Saturday, January 30, 2010
Indira Sona, the first rice hybrid for the shallow lowlands of Chhattisgarh State
The rainfed lowland ecosystem occupies about 40% of the state’s total rice area. Yield in these areas has remained stagnant in the past decades. Several pockets within this system can be considered as favorable lowland.The IGKV has identified the first rice hybrid, Indira Sona, for the shallow lowland ecosystem. Released for commercial cultivation in 2006. The hybrid has medium growth duration and high yield potential (8–9 t ha–1) (table). The area under hybrid rice is increasing gradually in the state and is currently around 50,000 ha.
Seed production of Indira Sona is easier because it involves less staggered flowering between the female and male parental lines (5−7 d). The restorer line (R710-437-1-1) has good floral characters—i.e., asynchronous flowering with good pollen load. Thus, only two staggered sowings of the restorer line are required for seed production. The panicle of restorer line R710-437-1-1 is pale green at the time of flowering; the sickle-shaped bunt at the end of the panicle is one of the restorer’s distinguishing features.
Friday, January 22, 2010
Processing Technology Of Turmeric
Turmeric processing technology-Botanical name of turmeric is curcutha longa L. It is an important spice which is used for yellow colour and special flavour. Rhizomes of turmeric are often found in violet yellow colour. Central rhizomes are like tubers and small rhizomes like fingers coming out from the central one. It contains 1.8 to 5.4% curcumin due to this it has yellow colour. Some amount of starch and 2.5 to 7.2% oil is also obtained. It is used in the form of spices for colouration and flavour. In this very form it is used in medicine and cosmetic goods manufacturing. There are two types of turmeric produced in central India. One has solid and dark colour and the other long, soft and light colour.
Washing-At first rhizomes are separated after digging out from the soil and these are washed, so that particles of soil, spray residues and unuseful particles attached with the rhizomes are removed. For this rhizomes are kept soaked in water throughout the night. Later on rhizomes are taken out and water is sprayed. This process can be achieved by soaking and spraying equipment. Spraying is done at low pressure and wide angle jet. At the time of washing rhizomes are divided in two parts. First part from middle is called mother rhizomes. The second part of it which is long and thin is called Doctor Rhizome. Mother rhizome is kept for seed while Doctor rhizomes are further processed and sold.
Boiling/Blanching/Cooking:-The next step of processing is boiling or blanching. Traditionally boiling is done in metal or mud pots alongwith ¾ water. Top of the pots are covered with a lid or dry leaves. Boiling process is continued till foams and white foams start coming out. These come out with a special quality of flavour. Rhizomes are tested by pressing with fingers. If rhizomes are soft and inner colour has become yellow instead of red then this process is said to be complete.
By using developed method of boiling or blanching both colour and quality are improved. Time taken is less. In the developed method bulbs are treated with 0.1% Soda (Sodium Carbonate, Sodium bicarbonate or Ammonium Carbonate) and water solution. The time required for this process is 30 minutes to 6 hours. Boiler is used in the developed method which is metal kettle open from the top. Soda solution is filled in it and it is heated from the bottom by electric heater or fuel oil. Perforated frame loaded with turmeric tubers or bulbs are sunk here. Water from all sides of perforations enters inside making turmeric tubers soft. After 30 or 40 minutes bulbs/tubers are taken up and tested alongwith the frame. Cooking at the optimal level is important as overcooking spoils the colour and undercooking renders the product brittle resulting in breakage of rhizomes during drying and polishing. Once the water in the vessel starts boiling it may take 45-60 minutes to complete the cooking. Cooking at optimal level is indicated by the frothing of the liquid and the release of the characteristic turmeric aroma.
Drying -Cooked rhizomes are cooled first and spread slowly in the yard for drying. It takes at least 10 to 15 days for drying in the sun. Tubers are brought up and down in the middle of drying so that all are dried well. Mother rhizome takes comparatively more time while Doctor rhizome dries up quickly. Therefore these are dried separately also. After drying these become hard and solid. Completely dried turmeric holds 6% moisture content.
Polishing-Dried rhizomes are rubbed against ground or below the foot to take out the hard layer over them and small roots are removed. By this process colour of turmeric becomes bright or shining. Later on removed roots, light garbage and thin layerings are cleaned.
Machine is also used for polishing. For this a drum having 0.9m diameter and 0.6m length is used. It is kept horizontally on a shaft and operated by a handle. Average capacity of this machine comes to 32kg per batch. Dry turmeric 32kg approx.is filled and polishing is done at least for 7 minutes. During this period water is also sprinkled which causes improvement in the colour of turmeric.
Manual polishing consists of rubbing the dried turmeric fingers on a hard surface or trampling them under feet wrapped in gunny bags. The improved method is by using hand operated barrel or drum mounted on a central axis, the sides of which are made by expanded metal mesh. When the drum filled with turmeric is rotated, polishing is effected by abrasion of the 3 surface against the mesh as well as by mutual rubbing against each other as they roll inside the drum. The turmeric is also polished in power operated drums.
Colouring-Exporting turmeric is given special colour by mixing yellow so that powder and processed materials can give better look and quality. Cleaning is done by two methods. One is dry colouring and the other wet colouring. In the first process dry powder of yellow colour is sprayed on boiled turmeric and rightly mixed. Powder is known as middle crome. In the wet colouring process its solution is prepared in water which is sprayed on rhizomes and mechanically mixed. After colouring is complete for one week these are dried. Later on these rhizomes are kept in sacks and closed for exporting (Adulteration-Lead chromate is sometimes used to produce a better finish. This should be actively discouraged.) For wet colouring prepare a solution of 2Kg Turmeric powder, 30 ml HCL ,140 ml Castor oil, 40 gm alum this mixture can colour 100 Kg of Turmeric.
Grinding or Powder making-Traditionally dried and polished turmeric are cut into pieces and beaten in mortar and pestle. After this is milled or ground with hand operated chakki. Hammer mill is also used for grinding. Powder should be so fine that it passes through 300 micron sieve and nothing is left over the sieve.
Processing of turmeric by traditional method-In India, at various places different methods and equipments are used, but basic method is mentioned below in a process
flow sheet.
Turmeric rhizomes ------> Washing-------> Boiling/Blanching/Cooking------> Drying-----> Colouring -------> Grinding/Powdering--------> Sieving-------> Packaging------------> Marketing
Washing-At first rhizomes are separated after digging out from the soil and these are washed, so that particles of soil, spray residues and unuseful particles attached with the rhizomes are removed. For this rhizomes are kept soaked in water throughout the night. Later on rhizomes are taken out and water is sprayed. This process can be achieved by soaking and spraying equipment. Spraying is done at low pressure and wide angle jet. At the time of washing rhizomes are divided in two parts. First part from middle is called mother rhizomes. The second part of it which is long and thin is called Doctor Rhizome. Mother rhizome is kept for seed while Doctor rhizomes are further processed and sold.
Boiling/Blanching/Cooking:-The next step of processing is boiling or blanching. Traditionally boiling is done in metal or mud pots alongwith ¾ water. Top of the pots are covered with a lid or dry leaves. Boiling process is continued till foams and white foams start coming out. These come out with a special quality of flavour. Rhizomes are tested by pressing with fingers. If rhizomes are soft and inner colour has become yellow instead of red then this process is said to be complete.
By using developed method of boiling or blanching both colour and quality are improved. Time taken is less. In the developed method bulbs are treated with 0.1% Soda (Sodium Carbonate, Sodium bicarbonate or Ammonium Carbonate) and water solution. The time required for this process is 30 minutes to 6 hours. Boiler is used in the developed method which is metal kettle open from the top. Soda solution is filled in it and it is heated from the bottom by electric heater or fuel oil. Perforated frame loaded with turmeric tubers or bulbs are sunk here. Water from all sides of perforations enters inside making turmeric tubers soft. After 30 or 40 minutes bulbs/tubers are taken up and tested alongwith the frame. Cooking at the optimal level is important as overcooking spoils the colour and undercooking renders the product brittle resulting in breakage of rhizomes during drying and polishing. Once the water in the vessel starts boiling it may take 45-60 minutes to complete the cooking. Cooking at optimal level is indicated by the frothing of the liquid and the release of the characteristic turmeric aroma.
Drying -Cooked rhizomes are cooled first and spread slowly in the yard for drying. It takes at least 10 to 15 days for drying in the sun. Tubers are brought up and down in the middle of drying so that all are dried well. Mother rhizome takes comparatively more time while Doctor rhizome dries up quickly. Therefore these are dried separately also. After drying these become hard and solid. Completely dried turmeric holds 6% moisture content.
Polishing-Dried rhizomes are rubbed against ground or below the foot to take out the hard layer over them and small roots are removed. By this process colour of turmeric becomes bright or shining. Later on removed roots, light garbage and thin layerings are cleaned.
Machine is also used for polishing. For this a drum having 0.9m diameter and 0.6m length is used. It is kept horizontally on a shaft and operated by a handle. Average capacity of this machine comes to 32kg per batch. Dry turmeric 32kg approx.is filled and polishing is done at least for 7 minutes. During this period water is also sprinkled which causes improvement in the colour of turmeric.
Manual polishing consists of rubbing the dried turmeric fingers on a hard surface or trampling them under feet wrapped in gunny bags. The improved method is by using hand operated barrel or drum mounted on a central axis, the sides of which are made by expanded metal mesh. When the drum filled with turmeric is rotated, polishing is effected by abrasion of the 3 surface against the mesh as well as by mutual rubbing against each other as they roll inside the drum. The turmeric is also polished in power operated drums.
Colouring-Exporting turmeric is given special colour by mixing yellow so that powder and processed materials can give better look and quality. Cleaning is done by two methods. One is dry colouring and the other wet colouring. In the first process dry powder of yellow colour is sprayed on boiled turmeric and rightly mixed. Powder is known as middle crome. In the wet colouring process its solution is prepared in water which is sprayed on rhizomes and mechanically mixed. After colouring is complete for one week these are dried. Later on these rhizomes are kept in sacks and closed for exporting (Adulteration-Lead chromate is sometimes used to produce a better finish. This should be actively discouraged.) For wet colouring prepare a solution of 2Kg Turmeric powder, 30 ml HCL ,140 ml Castor oil, 40 gm alum this mixture can colour 100 Kg of Turmeric.
Grinding or Powder making-Traditionally dried and polished turmeric are cut into pieces and beaten in mortar and pestle. After this is milled or ground with hand operated chakki. Hammer mill is also used for grinding. Powder should be so fine that it passes through 300 micron sieve and nothing is left over the sieve.
Processing of turmeric by traditional method-In India, at various places different methods and equipments are used, but basic method is mentioned below in a process
flow sheet.
Turmeric rhizomes ------> Washing-------> Boiling/Blanching/Cooking------> Drying-----> Colouring -------> Grinding/Powdering--------> Sieving-------> Packaging------------> Marketing
Forms of Ginger and Process Of making Dried Ginger
Forms of ginger- Ginger is usually available in three different forms:
•Fresh (green) root ginger
•Preserved ginger in brine or syrup
•Dried ginger spice.
Fresh ginger is usually consumed in the area where it is produced, although it is possible to transport fresh roots internationally. Both mature and immature rhizomes are consumed as a fresh vegetable.
Preserved ginger is only made from immature rhizomes. Most preserved ginger is exported. Hong Kong, China and Australia are the major producers of preserved ginger and dominate the world market.
Making preserved ginger is not simple as it requires a great deal of care and attention to quality. Only the youngest tenderest stems of ginger should be used. It is difficult to compete with the well established Chinese and Australian producers; therefore processors are advised against making this product.
Dried ginger spice is produced from the mature rhizome. As the rhizome matures the flavour and aroma become much stronger. Dried ginger is exported, usually in large pieces which are ground into a spice in the country of destination. Dried ginger can be ground and used directly as a spice and also for the extraction of ginger oil and ginger oleoresin.
This brief outlines the important steps that should be taken pre-harvest and post-harvest to produce dried ginger.
Processing dried ginger-There are two important factors to consider when selecting ginger rhizomes for processing:
a.Stage of maturity at harvest. Ginger rhizomes can be harvested from about 5 months after planting. At this stage they are immature. The roots are tender with a mild flavour and are suitable for fresh consumption or for processing into preserved ginger. After 7 months the rhizomes will become less tender and the flavour will be too strong to use them fresh. They are then only useful for drying. Mature rhizomes for drying are harvested between 8 and 9 months of age when they have a high aroma and flavour. If they are harvested later than this the fibre content will be too high.
b.Native properties of the type grown. Gingers grown in different parts of the world can differ in their native properties such as flavour, aroma and colour and this affects their suitability for processing. This is most important when preparing dried ginger, which needs rhizomes with a strong flavour and aroma. Himachel, Maran, Mananthody and Kuruppampady are good varieties for the preparation of dried ginger. Size of rhizome is an important factor to consider when drying ginger – medium sized rhizomes are the most suitable for drying. Large rhizomes often have a high moisture content which causes problems with drying.
Making dried ginger-Dried ginger is available in a number of different forms – the rhizomes can be left whole or they may be split or sliced into smaller pieces to accelerate drying. Sometimes the rhizomes are killed by peeling or boiling them for 10 to 15 minutes, which causes the rhizomes to become blackened. They have to be whitened (bleached) by treating with lime or sulphurous acid. The only product which is acceptable for the UK market is cleanly peeled dried ginger.
The process for dried ginger:
•The fresh rhizome is harvested at between 8 to 9 months of age.
•The roots and leaves are removed and the rhizomes are washed.
•The rhizomes have to be ‘killed’ or inactivated. This is done by peeling, rough scraping or chopping the rhizome into slices (either lengthwise or across the rhizome). The skin should be peeled off using a wooden scraper made from bamboo to prevent staining the rhizome. Whole unpeeled rhizomes can be killed by boiling in water for 10 minutes.
•After peeling and washing, the rhizomes are soaked for 2-3 hours in clean water then soaked in a solution of 1.5-2.0% lime (calcium oxide) for 6 hours. This produces a lighter coloured (bleached) rhizome. After soaking, the rhizomes are drained.
•The rhizomes are dried. The traditional method is to lay the pieces on clean bamboo mats or on a concrete floor and sun-dry until a final moisture content of 10%. Drying may take anything from 7 to 14 days depending upon the weather conditions. During drying, the rhizomes lose between 60 and 70% in weight.
•In rainy conditions, a mechanical drier such as a tray drier should be used to accelerate the drying process. Sliced ginger pieces take only 5-6 hours to dry when a hot air drier is used. Whole peeled ginger rhizomes take about 16-18 hours to dry in a mechanical drier. It is important to monitor the air flow and temperature during drying. The drying temperature should not exceed 60°C as this causes the rhizome flesh to darken. See the Practical Action Technical Brief on drying for further information on the different types of drier available.
•After drying, the rhizomes are cleaned to remove any dirt, pieces of dried peel and insects. An air separator can be used for large quantities, but at the small scale it is probably not cost effective.
•The dried rhizomes should be packaged into air-tight, moisture proof packaging for storage or export.
Quality assurance of dried ginger- Quality of the dried ginger is assessed by the appearance of the final product (colour, lack of mould or aflatoxin) and the aroma and flavour. These qualities are influenced by a combination of pre- and post-harvest factors:
•The most important factor is the cultivar of ginger used as this determines the flavour, aroma, pungency and levels of essential oil and fibre.
•The stage or maturity of the rhizome at harvest determines its suitability for end use. Rhizomes that are 8-9 months old produce the best quality dried ginger as they have a good combination of aroma and pungency and not too much fibre.
•After harvest the rhizomes should be handled with care to prevent injury. They should be washed immediately after harvest to ensure a pale colour. The wet rhizomes should not be allowed to lie in heaps for too long as they will begin to ferment.
•Care should be taken when removing the outer cork skin. It is essential to remove the skin to reduce the fibre content, but if the peeling is too thick, it may reduce the content of volatile oil which is contained near the surface of the rhizome.
•During drying the rhizomes should lose about 60-70% of their weight and achieve a final moisture content of 7-12%. Care should be taken to prevent the growth of mould during drying.
•The use of a mechanical drier produces a higher quality, cleaner product. The drying conditions can be carefully controlled and monitored and the time taken to dry is considerably reduced.
•After harvest, the cleaning, peeling and drying processes should be carried out as quickly as possible to prevent the growth of bacteria and mould and to prevent fermentation. If the drying process takes too long there is a risk of the ginger becoming infected by aflatoxin or other fungus.
•Dried ginger should be stored in a dry place to prevent the growth of mould. Storage for a long time results in the loss of flavour and pungency.
Grinding-Grinding can be a method of adding value to a product. However, it is not advisable to grind spices as they are more vulnerable to spoilage after grinding. The flavour and aroma compounds are not stable and will quickly disappear from ground products. The storage life of ground spices is much less than for the whole spices. It is very difficult for the consumer to judge the quality of a ground spice. It is also very easy for unscrupulous processors to contaminate the ground spice by adding other material. Therefore most consumers, from wholesalers to individual customers, prefer to buy whole spices.
Dried ginger is usually exported whole and ground in the country of import.
Packaging-Bulk rhizomes can be packed in jute sacks, wooden boxes or lined corrugated cardboard boxes for shipping. Dry slices or powder are packaged in multi-wall laminated bags. Some laminates are better than others due to film permeability. The packaging material should be impermeable to moisture and air. Sealing machines can be used to seal the bags.
Storage-Dried rhizomes, slices and splits should be stored in a cool place (10-15°C). At higher temperatures (23-26°C) the flavour compounds start to deteriorate and ginger loses some of its taste and aroma. The storage room should be dry and away from the direct sunlight. During storage the rhizomes should be protected from attack by insects and other pests. Natural pesticides such as the leaves of Glycosmis pentaphylla or Azadirachta indica can be added to the rhizomes to prevent damage from the cigarette beetle (Lasioderma serricome).
The storage room should be clean, dry, cool and free from pests. Mosquito netting should be fitted on the windows to prevent pests and insects from entering the room. Strong smelling foods, detergents and paints should not be stored in the same room.
•Fresh (green) root ginger
•Preserved ginger in brine or syrup
•Dried ginger spice.
Fresh ginger is usually consumed in the area where it is produced, although it is possible to transport fresh roots internationally. Both mature and immature rhizomes are consumed as a fresh vegetable.
Preserved ginger is only made from immature rhizomes. Most preserved ginger is exported. Hong Kong, China and Australia are the major producers of preserved ginger and dominate the world market.
Making preserved ginger is not simple as it requires a great deal of care and attention to quality. Only the youngest tenderest stems of ginger should be used. It is difficult to compete with the well established Chinese and Australian producers; therefore processors are advised against making this product.
Dried ginger spice is produced from the mature rhizome. As the rhizome matures the flavour and aroma become much stronger. Dried ginger is exported, usually in large pieces which are ground into a spice in the country of destination. Dried ginger can be ground and used directly as a spice and also for the extraction of ginger oil and ginger oleoresin.
This brief outlines the important steps that should be taken pre-harvest and post-harvest to produce dried ginger.
Processing dried ginger-There are two important factors to consider when selecting ginger rhizomes for processing:
a.Stage of maturity at harvest. Ginger rhizomes can be harvested from about 5 months after planting. At this stage they are immature. The roots are tender with a mild flavour and are suitable for fresh consumption or for processing into preserved ginger. After 7 months the rhizomes will become less tender and the flavour will be too strong to use them fresh. They are then only useful for drying. Mature rhizomes for drying are harvested between 8 and 9 months of age when they have a high aroma and flavour. If they are harvested later than this the fibre content will be too high.
b.Native properties of the type grown. Gingers grown in different parts of the world can differ in their native properties such as flavour, aroma and colour and this affects their suitability for processing. This is most important when preparing dried ginger, which needs rhizomes with a strong flavour and aroma. Himachel, Maran, Mananthody and Kuruppampady are good varieties for the preparation of dried ginger. Size of rhizome is an important factor to consider when drying ginger – medium sized rhizomes are the most suitable for drying. Large rhizomes often have a high moisture content which causes problems with drying.
Making dried ginger-Dried ginger is available in a number of different forms – the rhizomes can be left whole or they may be split or sliced into smaller pieces to accelerate drying. Sometimes the rhizomes are killed by peeling or boiling them for 10 to 15 minutes, which causes the rhizomes to become blackened. They have to be whitened (bleached) by treating with lime or sulphurous acid. The only product which is acceptable for the UK market is cleanly peeled dried ginger.
The process for dried ginger:
•The fresh rhizome is harvested at between 8 to 9 months of age.
•The roots and leaves are removed and the rhizomes are washed.
•The rhizomes have to be ‘killed’ or inactivated. This is done by peeling, rough scraping or chopping the rhizome into slices (either lengthwise or across the rhizome). The skin should be peeled off using a wooden scraper made from bamboo to prevent staining the rhizome. Whole unpeeled rhizomes can be killed by boiling in water for 10 minutes.
•After peeling and washing, the rhizomes are soaked for 2-3 hours in clean water then soaked in a solution of 1.5-2.0% lime (calcium oxide) for 6 hours. This produces a lighter coloured (bleached) rhizome. After soaking, the rhizomes are drained.
•The rhizomes are dried. The traditional method is to lay the pieces on clean bamboo mats or on a concrete floor and sun-dry until a final moisture content of 10%. Drying may take anything from 7 to 14 days depending upon the weather conditions. During drying, the rhizomes lose between 60 and 70% in weight.
•In rainy conditions, a mechanical drier such as a tray drier should be used to accelerate the drying process. Sliced ginger pieces take only 5-6 hours to dry when a hot air drier is used. Whole peeled ginger rhizomes take about 16-18 hours to dry in a mechanical drier. It is important to monitor the air flow and temperature during drying. The drying temperature should not exceed 60°C as this causes the rhizome flesh to darken. See the Practical Action Technical Brief on drying for further information on the different types of drier available.
•After drying, the rhizomes are cleaned to remove any dirt, pieces of dried peel and insects. An air separator can be used for large quantities, but at the small scale it is probably not cost effective.
•The dried rhizomes should be packaged into air-tight, moisture proof packaging for storage or export.
Quality assurance of dried ginger- Quality of the dried ginger is assessed by the appearance of the final product (colour, lack of mould or aflatoxin) and the aroma and flavour. These qualities are influenced by a combination of pre- and post-harvest factors:
•The most important factor is the cultivar of ginger used as this determines the flavour, aroma, pungency and levels of essential oil and fibre.
•The stage or maturity of the rhizome at harvest determines its suitability for end use. Rhizomes that are 8-9 months old produce the best quality dried ginger as they have a good combination of aroma and pungency and not too much fibre.
•After harvest the rhizomes should be handled with care to prevent injury. They should be washed immediately after harvest to ensure a pale colour. The wet rhizomes should not be allowed to lie in heaps for too long as they will begin to ferment.
•Care should be taken when removing the outer cork skin. It is essential to remove the skin to reduce the fibre content, but if the peeling is too thick, it may reduce the content of volatile oil which is contained near the surface of the rhizome.
•During drying the rhizomes should lose about 60-70% of their weight and achieve a final moisture content of 7-12%. Care should be taken to prevent the growth of mould during drying.
•The use of a mechanical drier produces a higher quality, cleaner product. The drying conditions can be carefully controlled and monitored and the time taken to dry is considerably reduced.
•After harvest, the cleaning, peeling and drying processes should be carried out as quickly as possible to prevent the growth of bacteria and mould and to prevent fermentation. If the drying process takes too long there is a risk of the ginger becoming infected by aflatoxin or other fungus.
•Dried ginger should be stored in a dry place to prevent the growth of mould. Storage for a long time results in the loss of flavour and pungency.
Grinding-Grinding can be a method of adding value to a product. However, it is not advisable to grind spices as they are more vulnerable to spoilage after grinding. The flavour and aroma compounds are not stable and will quickly disappear from ground products. The storage life of ground spices is much less than for the whole spices. It is very difficult for the consumer to judge the quality of a ground spice. It is also very easy for unscrupulous processors to contaminate the ground spice by adding other material. Therefore most consumers, from wholesalers to individual customers, prefer to buy whole spices.
Dried ginger is usually exported whole and ground in the country of import.
Packaging-Bulk rhizomes can be packed in jute sacks, wooden boxes or lined corrugated cardboard boxes for shipping. Dry slices or powder are packaged in multi-wall laminated bags. Some laminates are better than others due to film permeability. The packaging material should be impermeable to moisture and air. Sealing machines can be used to seal the bags.
Storage-Dried rhizomes, slices and splits should be stored in a cool place (10-15°C). At higher temperatures (23-26°C) the flavour compounds start to deteriorate and ginger loses some of its taste and aroma. The storage room should be dry and away from the direct sunlight. During storage the rhizomes should be protected from attack by insects and other pests. Natural pesticides such as the leaves of Glycosmis pentaphylla or Azadirachta indica can be added to the rhizomes to prevent damage from the cigarette beetle (Lasioderma serricome).
The storage room should be clean, dry, cool and free from pests. Mosquito netting should be fitted on the windows to prevent pests and insects from entering the room. Strong smelling foods, detergents and paints should not be stored in the same room.
Thursday, October 1, 2009
What is Soft Rice
CRRI, Orissa, India develops soft rice
A rice variety sourced from Assam may soon change the cooking pattern of rice in the country. Termed as soft rice or komal chawl, this rice has low starch content. It does not need boiling, and becomes eatable after being soaked in water for less than an hour.
Scientists have studied the rice named Aghonibora and has found that it retains quality. “It takes 140-145 days to mature; measured 90 cm in height and per hectare yield is about 4.5 tonne in preliminary testing. According to the CRRI, a number of rice varieties of Assamese origin--Aghonibora, Bhogalibora, Chakua and Misiri--classified as ‘soft’ rices or komal chawl, are low in amylose (a kind of starch) content. Grains of these varieties do not require cooking in boiled water, as they become fit to eat just after being soaked in normal water for less than an hour (One has only to soak the rice in warm water for 15 minutes and in cold water for around 40 minutes) to render it fit for consumption.
The CRRI has also introduced a flood-resistant paddy variety, Swarna Sub1, with a gene sourced from Philippines-based International Rice Research Institute (IRRI). Swarna Sub1 can withstand floodwater for close to two weeks.
A rice variety sourced from Assam may soon change the cooking pattern of rice in the country. Termed as soft rice or komal chawl, this rice has low starch content. It does not need boiling, and becomes eatable after being soaked in water for less than an hour.
Scientists have studied the rice named Aghonibora and has found that it retains quality. “It takes 140-145 days to mature; measured 90 cm in height and per hectare yield is about 4.5 tonne in preliminary testing. According to the CRRI, a number of rice varieties of Assamese origin--Aghonibora, Bhogalibora, Chakua and Misiri--classified as ‘soft’ rices or komal chawl, are low in amylose (a kind of starch) content. Grains of these varieties do not require cooking in boiled water, as they become fit to eat just after being soaked in normal water for less than an hour (One has only to soak the rice in warm water for 15 minutes and in cold water for around 40 minutes) to render it fit for consumption.
The CRRI has also introduced a flood-resistant paddy variety, Swarna Sub1, with a gene sourced from Philippines-based International Rice Research Institute (IRRI). Swarna Sub1 can withstand floodwater for close to two weeks.
Classification of Fungicides
FUNGICIDES
Definitions –
1.Fungicide - is a chemical, which is capable of killing fungi.
2. Antibiotic- is a chemical produced by a microorganism, which is inhibitory to other organisms. Fungicides can be classified as protectants, eradicants & systemic fungicides.
a. Protectant- Fungicide which is effective only if applied prior to fungal infection is called Protectant. Example – Mancozeb, Zineb.
b. Eradicant – is the one, which removes fungi from an infection court. An Eradicant can penetrate the host tissues to a limited extent & eliminate an established infection. Example – Lime Sulpher.
c. Systemic Fungicides- Systemic fungicides are the compounds, which are transported over a considerable distance in plant system after-penetration. They kill fungi, which are found remote from the point of application.
I) SULPHER FUNGICIDES
a) Inorganic Sulpher fungicides - includes elemental Sulpher, wettable Sulpher & lime Sulpher. Sulpher fungicides effectively control powdery mildew of different crops such as chilli, okra, grape, rubber, mango, citrus, black gram & green gram. Sulpher controls tikka leaf spot of groundnut & Diplocapron black spot of rose. Sulpher dust is used as seed treatment also.
b) Organic Sulpher fungicides- Dithiocarba mates are the organic Sulpher fungicides. They are divided into-
(i) Dialkyldithiocarbamtes- Thiram, Ziram & ferban & Ziram is used as Protectant & sprayed before the outbreak of the disease. It controls early blight of potato & tomato and anthracnose disease of cucurbits & beans. Thiram is commonly used for seed treatment. Thiram seed treatment controls seed-borne pathogens as well as soil born pathogens. It controls seed borne infection of colletotrichum capsici of chilli, root rot of groundnut, sorghum grain smut & Helminthosporium leaf spot of rice. As seed treatment it controls soil-borne infection of Phthium spp. of tomato, tobacco & brinjal (Damping off) Rhizoctonia solani of cotton & Sheath blight of rice. Ferban control diseases of apple. It controls leaf spot of banana, leaf mould of tomato & leaf spot of coffee.
(ii) Monoalkyldithio carbamates- maneb, Zineb, Mancozeb, vapam & nabam. Zineb controls anthracnose disease of bean, chilli, & cucurbits, rust disease of wheat, sorghum & bajra, downy mildew of grapevine, cucurbits, Onion & cabbage, cercospora leaf spot of groundnut, cabbage, cauliflower, Alternaria leaf spot of potato, tomato singer. Mancozeb is widely used for the control of late blight of potato, cercospora leaf spot of groundnut, cucurbits & sugar beet. Helminthosporium leaf spot of rice, ragi, maize & sorghum, downy mildew of grapevine & tobacco, rust disease of wheat groundnut, bajra & sorghum, Alternaria leaf spot of ginger, potato, tomato & wheat anthracnose of chilli, grapevine, sorghum, bean & cucurbits.
Vapam controls cotton wilt & damping off of papaya, tobacco & tomato. It controls nematodes also.
(II) Copper Fungicides
(a) Copper Sulphate Preparations – It include Bordeaux mixture, Bordeaux Paste, Burgundy mixture, & chestnut compound. Bordeaux mixture is highly effective against late blight of potato, downy mildew of grapevine, coffee rust, betel vine wilt, pepper wilt, tomato early & late blights & coconut will & bud rot.
(b) Copper Carbonate Preparations- It controls many fungal diseases of apple, pear, peach, plums & apricot.
c) Copper Oxychloride Preparations – Some formulations available in the market are Fytolan, Blue copper, Blitox etc. They are generally effective against all diseases against which Bordeaux mixture has been found effective.
Mercury Fungicides-
Various mercury fungicides sold in the market are ceresan, aretan, agallol, wet ceresan, Dry ceresan etc. They are effective as seed treatment.
IV Heterocylic nitrogen compounds-
a) Captan- It is commercially marketed as Captan, orthocide, vancide etc. It is Protectant fungicide. It controls maize helminthosporiose, chilli fruit rot & apple scab. It is mostly used as seed treatment.
b) Folpet – It is commercially marketed as Phaltan. It controls rose black spot & apple scab.
(c) Captofol – It is marketed as Difolotan, Foltaf etc.
It effectively controls sheath rot of rice & mango anthracnose.
V) Quinone Fungicides-
a) Chloranil – It is commercially marketed as spergon. It is good seed dressing fungicide. It controls grain smut of sorghum & damping off of beans & cotton.
b) Dichlone- The commercial name of the fungicide is phygon. It controls peach leaf curl, apple scab & bean anthracnose.
Miscellaneous Fungicides-
a) Quintozene - Commercial names of the fungicide are Brassicol, Terraclor, PCNB & Tritisan. It is used to control soil borne pathogens. It is effective against Rhizoctonia Solani, Macrophomina Phaseolina & Sclerotiana Sclerotiorum.
b) Dinocap - It is marketed in the name of karthane, Arathane, Mildex etc. Dinocap is effective in controlling powdery mildews.
c) Fenaminsosulph- it is commercially known as Dexon. It is highly effective against phycomycetes like pythium phytophthora & Aphanomyces.
d) Dicloran_ Its trade name is Botran. It controls Botrytis infection in several crops.
e) Chlorothalonil- It is marketed as Daconil & Kavach. It controls both tikka leaf spot & rust disease of groundnut & betelvine wilt.
SYSTEMIC FUNGICIDES-
Some of the systemic fungicides are-
a) Carbendazim – It is marketed as Bavistin, Derosal, B-Sten etc. It controls Powdery Mildews, smut diseases & bunts.
b) Benomyl- Benomyl is effective against Fusarium , Rhizoctonia, Macrophomina, Cercospora, Colletotrichum, Puricularia, Verticillium, Phomopsis, Septoria, Erysiphe, Plasmodiophora, Botrytis, Ustilago, Urocystis & Tilletia Spp.
c) Thiabendazole – It is commercially available as Tecto & Mertect. It controls wheat bunt.
d) Carboxin- it is commercially available as vitavax. It is the most effective fungicide to control internally seed borne loose smuts of cereals.
e) Oxycarboxin- it is commercially marketed as Plantvax. It is specifically effective against rust pathogens.
f) Pyracarbolid- it is commercially available as sicarol. It is effective against rust & smut & Rhizoctonia Spp.
g) Metalaxyl- it is marketed as Ridomil & Apron. Metalaxyl is highly effective against phycomyces fungi like Phytophthrora, Pythium, Scierospora, Pseudopernospora, Plasmopara, Sclerophthora & Albugo.
h) Tride morph- its trade name is calixin. It is mainly used against powdery mildews as foliar sprays
i) Pyroquilon- it is commercially available as Fongorene. It effectively controls rice blast.
j) Kitazin- it is commercially marketed as Kitazin. It is highly effective against rice blast.
k) Tricyclazole – it is commercially marketed as Beam. It is highly specific for the control of rice blast.
l) Probenazole- its commercial name is oryzemate. It is also specific against rice blast.
m) Triadimefon- it is commercially market as Bayleton. It is highly effective against powdery mildews. It also controls rust diseases.
n) Biloxazole- it is marketed as Baycor. It is effective against cercospora diseases & rusts.
o) Triademenol- The commercial name of the fungicide is Bayton. As seed treatment it controls smut & powdery mildews.
Definitions –
1.Fungicide - is a chemical, which is capable of killing fungi.
2. Antibiotic- is a chemical produced by a microorganism, which is inhibitory to other organisms. Fungicides can be classified as protectants, eradicants & systemic fungicides.
a. Protectant- Fungicide which is effective only if applied prior to fungal infection is called Protectant. Example – Mancozeb, Zineb.
b. Eradicant – is the one, which removes fungi from an infection court. An Eradicant can penetrate the host tissues to a limited extent & eliminate an established infection. Example – Lime Sulpher.
c. Systemic Fungicides- Systemic fungicides are the compounds, which are transported over a considerable distance in plant system after-penetration. They kill fungi, which are found remote from the point of application.
I) SULPHER FUNGICIDES
a) Inorganic Sulpher fungicides - includes elemental Sulpher, wettable Sulpher & lime Sulpher. Sulpher fungicides effectively control powdery mildew of different crops such as chilli, okra, grape, rubber, mango, citrus, black gram & green gram. Sulpher controls tikka leaf spot of groundnut & Diplocapron black spot of rose. Sulpher dust is used as seed treatment also.
b) Organic Sulpher fungicides- Dithiocarba mates are the organic Sulpher fungicides. They are divided into-
(i) Dialkyldithiocarbamtes- Thiram, Ziram & ferban & Ziram is used as Protectant & sprayed before the outbreak of the disease. It controls early blight of potato & tomato and anthracnose disease of cucurbits & beans. Thiram is commonly used for seed treatment. Thiram seed treatment controls seed-borne pathogens as well as soil born pathogens. It controls seed borne infection of colletotrichum capsici of chilli, root rot of groundnut, sorghum grain smut & Helminthosporium leaf spot of rice. As seed treatment it controls soil-borne infection of Phthium spp. of tomato, tobacco & brinjal (Damping off) Rhizoctonia solani of cotton & Sheath blight of rice. Ferban control diseases of apple. It controls leaf spot of banana, leaf mould of tomato & leaf spot of coffee.
(ii) Monoalkyldithio carbamates- maneb, Zineb, Mancozeb, vapam & nabam. Zineb controls anthracnose disease of bean, chilli, & cucurbits, rust disease of wheat, sorghum & bajra, downy mildew of grapevine, cucurbits, Onion & cabbage, cercospora leaf spot of groundnut, cabbage, cauliflower, Alternaria leaf spot of potato, tomato singer. Mancozeb is widely used for the control of late blight of potato, cercospora leaf spot of groundnut, cucurbits & sugar beet. Helminthosporium leaf spot of rice, ragi, maize & sorghum, downy mildew of grapevine & tobacco, rust disease of wheat groundnut, bajra & sorghum, Alternaria leaf spot of ginger, potato, tomato & wheat anthracnose of chilli, grapevine, sorghum, bean & cucurbits.
Vapam controls cotton wilt & damping off of papaya, tobacco & tomato. It controls nematodes also.
(II) Copper Fungicides
(a) Copper Sulphate Preparations – It include Bordeaux mixture, Bordeaux Paste, Burgundy mixture, & chestnut compound. Bordeaux mixture is highly effective against late blight of potato, downy mildew of grapevine, coffee rust, betel vine wilt, pepper wilt, tomato early & late blights & coconut will & bud rot.
(b) Copper Carbonate Preparations- It controls many fungal diseases of apple, pear, peach, plums & apricot.
c) Copper Oxychloride Preparations – Some formulations available in the market are Fytolan, Blue copper, Blitox etc. They are generally effective against all diseases against which Bordeaux mixture has been found effective.
Mercury Fungicides-
Various mercury fungicides sold in the market are ceresan, aretan, agallol, wet ceresan, Dry ceresan etc. They are effective as seed treatment.
IV Heterocylic nitrogen compounds-
a) Captan- It is commercially marketed as Captan, orthocide, vancide etc. It is Protectant fungicide. It controls maize helminthosporiose, chilli fruit rot & apple scab. It is mostly used as seed treatment.
b) Folpet – It is commercially marketed as Phaltan. It controls rose black spot & apple scab.
(c) Captofol – It is marketed as Difolotan, Foltaf etc.
It effectively controls sheath rot of rice & mango anthracnose.
V) Quinone Fungicides-
a) Chloranil – It is commercially marketed as spergon. It is good seed dressing fungicide. It controls grain smut of sorghum & damping off of beans & cotton.
b) Dichlone- The commercial name of the fungicide is phygon. It controls peach leaf curl, apple scab & bean anthracnose.
Miscellaneous Fungicides-
a) Quintozene - Commercial names of the fungicide are Brassicol, Terraclor, PCNB & Tritisan. It is used to control soil borne pathogens. It is effective against Rhizoctonia Solani, Macrophomina Phaseolina & Sclerotiana Sclerotiorum.
b) Dinocap - It is marketed in the name of karthane, Arathane, Mildex etc. Dinocap is effective in controlling powdery mildews.
c) Fenaminsosulph- it is commercially known as Dexon. It is highly effective against phycomycetes like pythium phytophthora & Aphanomyces.
d) Dicloran_ Its trade name is Botran. It controls Botrytis infection in several crops.
e) Chlorothalonil- It is marketed as Daconil & Kavach. It controls both tikka leaf spot & rust disease of groundnut & betelvine wilt.
SYSTEMIC FUNGICIDES-
Some of the systemic fungicides are-
a) Carbendazim – It is marketed as Bavistin, Derosal, B-Sten etc. It controls Powdery Mildews, smut diseases & bunts.
b) Benomyl- Benomyl is effective against Fusarium , Rhizoctonia, Macrophomina, Cercospora, Colletotrichum, Puricularia, Verticillium, Phomopsis, Septoria, Erysiphe, Plasmodiophora, Botrytis, Ustilago, Urocystis & Tilletia Spp.
c) Thiabendazole – It is commercially available as Tecto & Mertect. It controls wheat bunt.
d) Carboxin- it is commercially available as vitavax. It is the most effective fungicide to control internally seed borne loose smuts of cereals.
e) Oxycarboxin- it is commercially marketed as Plantvax. It is specifically effective against rust pathogens.
f) Pyracarbolid- it is commercially available as sicarol. It is effective against rust & smut & Rhizoctonia Spp.
g) Metalaxyl- it is marketed as Ridomil & Apron. Metalaxyl is highly effective against phycomyces fungi like Phytophthrora, Pythium, Scierospora, Pseudopernospora, Plasmopara, Sclerophthora & Albugo.
h) Tride morph- its trade name is calixin. It is mainly used against powdery mildews as foliar sprays
i) Pyroquilon- it is commercially available as Fongorene. It effectively controls rice blast.
j) Kitazin- it is commercially marketed as Kitazin. It is highly effective against rice blast.
k) Tricyclazole – it is commercially marketed as Beam. It is highly specific for the control of rice blast.
l) Probenazole- its commercial name is oryzemate. It is also specific against rice blast.
m) Triadimefon- it is commercially market as Bayleton. It is highly effective against powdery mildews. It also controls rust diseases.
n) Biloxazole- it is marketed as Baycor. It is effective against cercospora diseases & rusts.
o) Triademenol- The commercial name of the fungicide is Bayton. As seed treatment it controls smut & powdery mildews.
Wednesday, August 19, 2009
MASS COMMUNICATION AND METHODS OF MASS COMMUNICATION’S
Importance:
Mass media enable extension workers to greatly increase their teaching efficiency. Publications, news papers articles, circular letters, radio, television, exhibits, posters etc., provide helpful repetition for those contacted personally or through groups. They also facilitate dissemination of information to a much larger & different clientele. Even though the intensity of the teaching contact, through mass media is less, the large number of people reached and the low cost per unit of coverage more than off-set the lack of intensity. The extension teaching plan which neglects the communication possibility through mass media fails to fully capitalize on what has already been invested in the more intensive contact methods.
Definitions of Communication
Leagans says, “It is a process by which two or more people exchange ideas, facts, feelings or impressions in a way that each gains a common understanding of message. In essence it is the act of getting a sender and a receiver tuned together for a particular message or series of messages.”
Communication is the imparting or interchange of thoughts, opinions or information by speech, writing or science. (American College Dictionary)
According to Rogers & Shoemaker (1970) Communication is the process by which messages are transferred from a source to receiver.
Van de Ban & Hawkins (1988) defined Communication as the process of sending & receiving messages through channels which establishes common meanings between a source and a receiver.
Communication is the process by which the message is transmitted from the source to the receiver (Rogers, 1983)
Communication is a mutual interchange of ideas by any effective means (Thayer 1968)
Communication is anything that conveys meaning that carries a message from one person to another (Brooker 1949)
Communication Methods
A method is a procedure or process for attaining an objective. The choice of channels or method of communication, also known as extension teaching method, generally depends on the number and location of the target audience, and the time available for communication.
Selection of effective combination of extension method
A combination of extension teaching methods or that of mass media and inter personal sources is perhaps the most effective way of reaching people with new ideas and persuading them to utilize these innovations.
The basic idea behind this is:
The more the senses of the learner are involved in the learning process, the greater the learning.
To ensure action on the part of learner, several exposures may be necessary in order to motivate, remind and persuade them.
It will depend on the situation as well as knowledge and experience of the extension agent.
Basically Communication Methods Are Classified As:-
1. Interpersonal Communication
2. Mass media Communication
Interpersonal Communication
It consists of a face to face exchange between two or more individuals. The message flow is from one to a few individuals. Feed back is immediate and usually plentiful, and the messages are often relatively high in socio-emotional content
Mass media Communication
It involves some type of hardware equipment that enables a source of one or a few individuals to reach a large audience. Feedback is limited and delayed and the messages are often relatively low in socio-emotional content.
[A]. Interpersonal Methods
In this method, the extension agent communicates with the people individually, maintaining separate identity of each person. This method is followed when the number of people to be contacted are few, are conveniently located close to the communicator and sufficient time is available for communication. eg. Farm & Home visit, Farmers call etc
Advantages
1. Helps in selecting demonstrators & local leaders
2. Helps in changing attitudes of people
3. Helps in teaching complex practices.
4. Facilitates transfer of technology
5. Getting feedback information
Limitations
1. This method is time consuming & relatively expensive
2. Has low coverage of audience
3. Extension agent may develop favoritism or bias towards some persons
[B]. Group Methods
It may be defined as an aggregate of small number of people in reciprocal communication and interaction around some common interest. In this method extension agent communicates with the people in groups and not as individual persons. eg. Result demonstration, Method demonstration, group meeting etc.
Objectives
1. It helps for selection of village leaders.
2. It gives the idea for the need of people.
3. Less expensive than individual method due to more coverage
4. More effective than mass method in stimulating action.
Limitations
1. Wide diversity of interest of people may create a difficulty to learning situation
2. Every body wants for their individual development.
[C].Mass Methods
In this method, extension agent communicates with vast & heterogeneous mass of peoples, without taking into consideration their individual identity. This method is followed where a large & widely dispersed audience is to be communicated within a short period of time. The size of audience may be a few hundred in mass meeting, few thousands in campaign & exhibition and millions in newspaper, radio & TV.
Advantage:
1. Suitable for creating general awareness amongst the people.
2. Helps in transferring knowledge, forming & changing opinion.
3. Large number of people can be communicated within short time
Limitations:-
1. Less intensive method.
2. Cannot be held frequently
3. Little scope for personal contact with the audience.
4. Little control over the responses of audience.
5. Difficult in getting feedback information & evaluation of results
Means of Mass Communication:
Newspaper:
Newspaper is a bunch of loose printed papers properly folded, which contains news, views, advertisements etc and is offered for sale at regular intervals, particularly daily or weekly. Newspapers are usually printed on a special type of paper known as newsprint.
Daily newspapers are resource strong and are published from national/ state capitals or big cities. Their approach is cosmopolite and the circulation may range from about a lack to several lakhs. Some of the daily newspaper are quite big and are published simultaneously from several cities.
Selection of matter for writing in news paper
Prepare a draft write up on the topic in simple language, furnishing current and important information. The lead i.e. the opening sentence or paragraph is important and should be comprehensive. Give a suitable caption
1. The draft should contain information on what, who, when, where and why.
2. Revise the draft and produce a brief, lucid, interesting and informative write up.
3. In required, enclose photographs on glossy paper with the write up.
Advantages:
1- Large circulation.
2- Cheaper than any other mass communication device.
Limitations:
1. Only literate people generally can take advantage of this medium.
2. Increase in the price of newspapers may restrict their circulation.
Television
Television is an electronic audio-visual medium which provides pictures with synchronized sound. This medium is cosmopolite in approach and can be used to create instant mass awareness. Television combines the immediacy of radio with the mobility of Cinema and can carry messages over long distance at a relatively low unit cost.
Television is multi media equipment as it can include motion picture, recording, slide, photograph, drawing, poster etc. Television can show recorded as well as live programmes.
Both recording and playback equipments are transportable, allowing flexibility of use
Purpose:
1. People learn through the eye, & will remember things better if they see them.
2. The message on the tv screen are presented in the simplest manner possible.
Advantages
1. To create a general awareness amongst the people about agricultural and rural development.
2. To provide need based programmes to the rural audience.
3. To show the rural people in general & the farmer in particular what to do,how to do,& when to do.
Limitations
1. Requires lots of planning, preparation, trained personal and availability of equipments.
2. Audience participation depends on costly receiving sets and availability of electricity.
3. TV is an electronic audio visual medium,which provides pictures with synchronize sound.
4. Seldom goes beyond creating general awareness of audience
Video Films:
Video films are really a series of still pictures on a long strip of film. Each picture is flashed momentarily on the screen and the rapid succession of still pictures-(each of which shows the subject in a slightly different position) – gives an illusion of movements. Usually 70 mm and 35 mm. films are used for commercial entertainment, 16 mm. Film for educational movies, and 8 mm. Film for domestic pictures.
Advantages:
1. A complete process involving motion can be shown in a short time.
2. People identify themselves with those in the films.
3. Compel attention.
4. Heighten reality.
5. Speed or slow down time.
6. Bring the distant past and the distant present into learning situation.
7. Enlarge or reduce actual size of objects.
Limitations:
1. Special equipment is necessary.
2. The equipment is costly.
3. Some sort of power is required to operate the projectors.
4. Transportation maintenance & storage of equipment & materials require special consideration & skill.
5. Suitable halls for showing motion picture are not available in many places.
6. Bring the distant past and the distant present into learning situation.
7. Enlarge or reduce actual size of objects.
Purpose:
1. To present facts in an interesting way.
2. To attract audience.
3. To arouse interest.
4. To change attitudes.
5. To bring new practices to village In a short time.
6. To reach illiterate as well as literate people.
Points to remember:
1. Be thoroughly familiar with the subject you plan to teach and how exactly the film supports the ideas you want to get across.
2. Preview the film
3. before showing the film, explain the subject, tell why it is important and stimulate viewers to look for certain thing in the film.
4. At the end of the show, have a forum
5. Follow up (capitalise the enthusiasm generated)
Mass Meeting:
Mass meeting is held to communicate interesting and useful information to a large audience at a time. The size of the audience for mass meeting may be a few hundreds, but at the time of fairs or festivals it may be few thousands
Objectives
1. To focus attention of the people on some important topic.
2. To enlist people’s participation in community work.
3. To appear personally before a large audience
Advantage
1. Reaches many who read little or none at all.
2. A means of informing non farm people (tax payers) about agricultural matters.
3. Reaches people who are unable to attend extension meetings.
4. Builds interest in other extension media.
Limitations
1. In-depth discussion of the topic not possible.
2. Can’t be held frequently.
3. Difficult to get feed back information.
Radio:
Radio is an electronic audio-medium for broadcasting programmes to the audience. This medium is cosmopolite in approach and is suitable for communication to millions of people widely dispersed and situated in remote areas. Radio is suitable for creating general awareness amongst the people, help change their attitude and reinforces learning. It reaches a large number of people at a very low cost.
Purpose:
1. To reach large numbers of people quickly & inexpensively.
2. To reach people not reach by other means.
3. To stimulate participation in extension through all other media.
4. To build enthusiasm & maintain interest.
Advantages:
1. Can reach more quickly than any other means of communication.
2. Specially suited to give emergency & timely information(e.g. weather,pest-out-break etc.)
3. Relatively cheap.
4. Reaches many who read little or none at all.
5. Reaches people who are unable to attend extension meetings.
6. A means of informing non farm people( tax payers) about agricultural matters.
7. Builds interest in other extension media.
8. Possible to do other things while listening.
Limitations:
1. Limited number of broadcasting stations.
2. Not within reach of all farmers.
3. Recommendations may not apply to individual needs.
4. No turning back if not needed.
5. Frequently loses out in competition with entertainment.
6. Difficult to check on results.
PROJECTORS:
The lantern slides is one of the most popular & versatile visual in extension education. It is a transparent picture on glass or film) which is projected by focusing light through it from electric bulb, petromax or lantern.
Reasons for the popularity of lantern slides are:
1. They can be made by the individual worker at low cost.
2. They can be made either in natural colour in black and white.
3. Both the slides and projections equipment are relatively light and can be easily transported.
4. Slide sequence can be readily changed to keep them timely and localized.
5. We can use the full set of slides or select only a few slides required for our subject.
6. Each slide can be retained for any length of time according to the teaching situation.
Limitations:
1. They do not show action.
2. They normally require live narration, unless synchronized with tape recorder.
3. They require close co-operation within a projections throughout the presentation if the speaker desires to be in front of his audience.
Mass media enable extension workers to greatly increase their teaching efficiency. Publications, news papers articles, circular letters, radio, television, exhibits, posters etc., provide helpful repetition for those contacted personally or through groups. They also facilitate dissemination of information to a much larger & different clientele. Even though the intensity of the teaching contact, through mass media is less, the large number of people reached and the low cost per unit of coverage more than off-set the lack of intensity. The extension teaching plan which neglects the communication possibility through mass media fails to fully capitalize on what has already been invested in the more intensive contact methods.
Definitions of Communication
Leagans says, “It is a process by which two or more people exchange ideas, facts, feelings or impressions in a way that each gains a common understanding of message. In essence it is the act of getting a sender and a receiver tuned together for a particular message or series of messages.”
Communication is the imparting or interchange of thoughts, opinions or information by speech, writing or science. (American College Dictionary)
According to Rogers & Shoemaker (1970) Communication is the process by which messages are transferred from a source to receiver.
Van de Ban & Hawkins (1988) defined Communication as the process of sending & receiving messages through channels which establishes common meanings between a source and a receiver.
Communication is the process by which the message is transmitted from the source to the receiver (Rogers, 1983)
Communication is a mutual interchange of ideas by any effective means (Thayer 1968)
Communication is anything that conveys meaning that carries a message from one person to another (Brooker 1949)
Communication Methods
A method is a procedure or process for attaining an objective. The choice of channels or method of communication, also known as extension teaching method, generally depends on the number and location of the target audience, and the time available for communication.
Selection of effective combination of extension method
A combination of extension teaching methods or that of mass media and inter personal sources is perhaps the most effective way of reaching people with new ideas and persuading them to utilize these innovations.
The basic idea behind this is:
The more the senses of the learner are involved in the learning process, the greater the learning.
To ensure action on the part of learner, several exposures may be necessary in order to motivate, remind and persuade them.
It will depend on the situation as well as knowledge and experience of the extension agent.
Basically Communication Methods Are Classified As:-
1. Interpersonal Communication
2. Mass media Communication
Interpersonal Communication
It consists of a face to face exchange between two or more individuals. The message flow is from one to a few individuals. Feed back is immediate and usually plentiful, and the messages are often relatively high in socio-emotional content
Mass media Communication
It involves some type of hardware equipment that enables a source of one or a few individuals to reach a large audience. Feedback is limited and delayed and the messages are often relatively low in socio-emotional content.
[A]. Interpersonal Methods
In this method, the extension agent communicates with the people individually, maintaining separate identity of each person. This method is followed when the number of people to be contacted are few, are conveniently located close to the communicator and sufficient time is available for communication. eg. Farm & Home visit, Farmers call etc
Advantages
1. Helps in selecting demonstrators & local leaders
2. Helps in changing attitudes of people
3. Helps in teaching complex practices.
4. Facilitates transfer of technology
5. Getting feedback information
Limitations
1. This method is time consuming & relatively expensive
2. Has low coverage of audience
3. Extension agent may develop favoritism or bias towards some persons
[B]. Group Methods
It may be defined as an aggregate of small number of people in reciprocal communication and interaction around some common interest. In this method extension agent communicates with the people in groups and not as individual persons. eg. Result demonstration, Method demonstration, group meeting etc.
Objectives
1. It helps for selection of village leaders.
2. It gives the idea for the need of people.
3. Less expensive than individual method due to more coverage
4. More effective than mass method in stimulating action.
Limitations
1. Wide diversity of interest of people may create a difficulty to learning situation
2. Every body wants for their individual development.
[C].Mass Methods
In this method, extension agent communicates with vast & heterogeneous mass of peoples, without taking into consideration their individual identity. This method is followed where a large & widely dispersed audience is to be communicated within a short period of time. The size of audience may be a few hundred in mass meeting, few thousands in campaign & exhibition and millions in newspaper, radio & TV.
Advantage:
1. Suitable for creating general awareness amongst the people.
2. Helps in transferring knowledge, forming & changing opinion.
3. Large number of people can be communicated within short time
Limitations:-
1. Less intensive method.
2. Cannot be held frequently
3. Little scope for personal contact with the audience.
4. Little control over the responses of audience.
5. Difficult in getting feedback information & evaluation of results
Means of Mass Communication:
Newspaper:
Newspaper is a bunch of loose printed papers properly folded, which contains news, views, advertisements etc and is offered for sale at regular intervals, particularly daily or weekly. Newspapers are usually printed on a special type of paper known as newsprint.
Daily newspapers are resource strong and are published from national/ state capitals or big cities. Their approach is cosmopolite and the circulation may range from about a lack to several lakhs. Some of the daily newspaper are quite big and are published simultaneously from several cities.
Selection of matter for writing in news paper
Prepare a draft write up on the topic in simple language, furnishing current and important information. The lead i.e. the opening sentence or paragraph is important and should be comprehensive. Give a suitable caption
1. The draft should contain information on what, who, when, where and why.
2. Revise the draft and produce a brief, lucid, interesting and informative write up.
3. In required, enclose photographs on glossy paper with the write up.
Advantages:
1- Large circulation.
2- Cheaper than any other mass communication device.
Limitations:
1. Only literate people generally can take advantage of this medium.
2. Increase in the price of newspapers may restrict their circulation.
Television
Television is an electronic audio-visual medium which provides pictures with synchronized sound. This medium is cosmopolite in approach and can be used to create instant mass awareness. Television combines the immediacy of radio with the mobility of Cinema and can carry messages over long distance at a relatively low unit cost.
Television is multi media equipment as it can include motion picture, recording, slide, photograph, drawing, poster etc. Television can show recorded as well as live programmes.
Both recording and playback equipments are transportable, allowing flexibility of use
Purpose:
1. People learn through the eye, & will remember things better if they see them.
2. The message on the tv screen are presented in the simplest manner possible.
Advantages
1. To create a general awareness amongst the people about agricultural and rural development.
2. To provide need based programmes to the rural audience.
3. To show the rural people in general & the farmer in particular what to do,how to do,& when to do.
Limitations
1. Requires lots of planning, preparation, trained personal and availability of equipments.
2. Audience participation depends on costly receiving sets and availability of electricity.
3. TV is an electronic audio visual medium,which provides pictures with synchronize sound.
4. Seldom goes beyond creating general awareness of audience
Video Films:
Video films are really a series of still pictures on a long strip of film. Each picture is flashed momentarily on the screen and the rapid succession of still pictures-(each of which shows the subject in a slightly different position) – gives an illusion of movements. Usually 70 mm and 35 mm. films are used for commercial entertainment, 16 mm. Film for educational movies, and 8 mm. Film for domestic pictures.
Advantages:
1. A complete process involving motion can be shown in a short time.
2. People identify themselves with those in the films.
3. Compel attention.
4. Heighten reality.
5. Speed or slow down time.
6. Bring the distant past and the distant present into learning situation.
7. Enlarge or reduce actual size of objects.
Limitations:
1. Special equipment is necessary.
2. The equipment is costly.
3. Some sort of power is required to operate the projectors.
4. Transportation maintenance & storage of equipment & materials require special consideration & skill.
5. Suitable halls for showing motion picture are not available in many places.
6. Bring the distant past and the distant present into learning situation.
7. Enlarge or reduce actual size of objects.
Purpose:
1. To present facts in an interesting way.
2. To attract audience.
3. To arouse interest.
4. To change attitudes.
5. To bring new practices to village In a short time.
6. To reach illiterate as well as literate people.
Points to remember:
1. Be thoroughly familiar with the subject you plan to teach and how exactly the film supports the ideas you want to get across.
2. Preview the film
3. before showing the film, explain the subject, tell why it is important and stimulate viewers to look for certain thing in the film.
4. At the end of the show, have a forum
5. Follow up (capitalise the enthusiasm generated)
Mass Meeting:
Mass meeting is held to communicate interesting and useful information to a large audience at a time. The size of the audience for mass meeting may be a few hundreds, but at the time of fairs or festivals it may be few thousands
Objectives
1. To focus attention of the people on some important topic.
2. To enlist people’s participation in community work.
3. To appear personally before a large audience
Advantage
1. Reaches many who read little or none at all.
2. A means of informing non farm people (tax payers) about agricultural matters.
3. Reaches people who are unable to attend extension meetings.
4. Builds interest in other extension media.
Limitations
1. In-depth discussion of the topic not possible.
2. Can’t be held frequently.
3. Difficult to get feed back information.
Radio:
Radio is an electronic audio-medium for broadcasting programmes to the audience. This medium is cosmopolite in approach and is suitable for communication to millions of people widely dispersed and situated in remote areas. Radio is suitable for creating general awareness amongst the people, help change their attitude and reinforces learning. It reaches a large number of people at a very low cost.
Purpose:
1. To reach large numbers of people quickly & inexpensively.
2. To reach people not reach by other means.
3. To stimulate participation in extension through all other media.
4. To build enthusiasm & maintain interest.
Advantages:
1. Can reach more quickly than any other means of communication.
2. Specially suited to give emergency & timely information(e.g. weather,pest-out-break etc.)
3. Relatively cheap.
4. Reaches many who read little or none at all.
5. Reaches people who are unable to attend extension meetings.
6. A means of informing non farm people( tax payers) about agricultural matters.
7. Builds interest in other extension media.
8. Possible to do other things while listening.
Limitations:
1. Limited number of broadcasting stations.
2. Not within reach of all farmers.
3. Recommendations may not apply to individual needs.
4. No turning back if not needed.
5. Frequently loses out in competition with entertainment.
6. Difficult to check on results.
PROJECTORS:
The lantern slides is one of the most popular & versatile visual in extension education. It is a transparent picture on glass or film) which is projected by focusing light through it from electric bulb, petromax or lantern.
Reasons for the popularity of lantern slides are:
1. They can be made by the individual worker at low cost.
2. They can be made either in natural colour in black and white.
3. Both the slides and projections equipment are relatively light and can be easily transported.
4. Slide sequence can be readily changed to keep them timely and localized.
5. We can use the full set of slides or select only a few slides required for our subject.
6. Each slide can be retained for any length of time according to the teaching situation.
Limitations:
1. They do not show action.
2. They normally require live narration, unless synchronized with tape recorder.
3. They require close co-operation within a projections throughout the presentation if the speaker desires to be in front of his audience.
AQUATIC WEEDS AND THEIR CONTROL
INTRODUCTION
Aquatic weed are those unwanted plants which grow in water and complete at least a part of their life cycle in water. Many aquatic plants are desirable since they may play temporarily a beneficial role in reducing agricultural, domestic and industrial pollution. Letting a crop of plants grow in a lake or pond and then killing it over a period of time, and consequently releasing nutrients back into the water, may help in fish production. However, many aquatic plans are considered weeds when they deprive human beings of all facets of efficient use of water and cause harmful effects, some of which are discussed below.
Submersed, immersed, emerged and marginal weeds in and along irrigation canals, ditches, and drainage channels impede water flow, increase evaporation, cause damage to canals and structures, and clog gates, siphons, valves, sprinkler heads bridge piers, pumps, etc.
Floating and deep-rooted submersed weeds interfere with navigation. Some of the tougher and densely growing weeds, e.g. water hyacinth and alligator weed become impenetrable and prevent boats and even steamers moving through. Submersed and floating aquatic weeds in farm ponds, village tanks and water reservoirs reduce their utility for water storage and irrigation.
Aquatic weed growth also prevents or impairs the use of inland waters for fishing. The weed assimilates large quantities of nutrients from water, thus reducing their availability for desirable planktonic algae. They cause oxygen deficiency and prevent gaseous exchange with atmosphere, resulting in an adverse effect on fish production. Excessive growth of these weeds may provide excessive cover, resulting in an overpopulation of small fish and interference with fish harvesting.
Aquatic weeds provide a suitable habitat for development of mosquitoes in impounded waters, causing malaria, filariasis and encephalitis. These weeds serve as the primary vector for the disease-causing organisms.
Aquatic weeds reduce the recreational values of lakes, tanks, streams, etc. as the water is made turbid or dirty with an undesirable odour
TYPES OF AQUATIC WEED
There are two types of aquatic plants: algae and hydrophytes.
ALGAE-Algae normally inhabit the surface of fresh and saline waters exposed to sunlight. While some kinds of algae are found in solid and on terrestrial surfaces exposed to air, the majority aquatic and adapted to live in ponds, lakes, reservoirs, steams, swimming pools and oceans.
Freshwater algae are of two types: planktonic and filamentous. planktonic algae, called phytoplankton, include the truly aquatic single-celled algae and the simplest filamentous or colonial forms. A heavy growth of algae may colour the water shades of green, yellow, red and black. Hey may also form water blooms or scums. They convert solar energy into food, remove CO2 from water during photosynthesis (in day time) and produce oxygen as a by product. During the night or in cloudy water, they release co2 in the water through respiration as consume O2.
Certain planktonic algae are beneficial as they can maintain biotic balance in natural aquatic environment because of their ability to produce oxygen and maintain an aerobic condition. They are the original sources of food for most fish and aquatic animals. Although planktonic algae are beneficial, their overabundance may be undesirable for many domestic and commercial water uses.
Excessive phytoplanktonic blooms often result in zooplanktonic (the microscopic animal forms) development that may deplete result in zooplanktonic the water of oxygen and lead to over fertilization or eutrophication and destruction of fish and other aquatic wild life. Dense growth of planktonic algae will shade bottom muds sufficiently to prevent germination of seeds and growth of many species of rooted submersed weeds, thus affecting the stability of the habitat
Generally, planktonic algae do not interfere with the use of surface waters or irrigation purposes. But some of them, the blue-green algae and green algae produce odours and scums that make unfit for swimming. Several of the blue-algae produce toxic substances that kill fish, birds and domestic animals.
Another group of algae called filametous algae (nanoplankton) consists of single celled joined end to end which may form single thread, branched filaments, nets, or erect stem like whorled branches or forked leaf like forms. They don’t have roots, stems or leaf as do higher plants. The important genera of the filamentous algae are: Chara, Nitella, Spirogyra, Hydrodictyon, Cladophora, Pithophora.
HYDROPHYTES-The hydrophytes, which represent more than 100 families, are vascular plants. They grow wholly or partially submersed in either fresh or saline water or in plaustrine areas. They are structurally different from mesophytes and xerophytes that grow in moisture-deficient situations. The protecting and conducting tissues of hydrophytes are less developed. They have extensive provision for aeration and buoyancy, particularly in the leaf mesophyll, ground tissue of the petiole and the cortex of the stem and root. Buoyancy is provided by aerenchyma or by air chambers. The air chambers may be either schiogenous or lysigenous, or both. Hydrophytes weeds can be grouped as submersed, emersed, marginal and floating weeds.
1- SUBMERSED WEEDS
Submersed weeds are mostly vascular plants the produce all or most of their vegetative growth beneath the water surface. Most submerged vascular weeds are seed plants and have true roots, stems and leaves. Abundance and density of these weeds is primarily dependent on depth and turbidity of water and physical characteristics of the bottom. A maximum depth of 3.5-4 m in clear waters is the limit for most of the submersed plants. They are capable of absorbing nutrients and herbicides through the leaves and stems as well as roots. They compete for nutrients with planktonic algae and decrease their production and a corresponding decrease in fish production.
The submersed weeds belong to the following genera: Potamogeton, Elodea, Myriophyllum, Ceratophyllum, Utricularia, Ranunculus, Heteratheral Alisma, Zannichellia, Lemna, etc.
2- EMERSED WEEDS
Emersed weeds are those plants rooted in the bottom muds with serial stems and leaves at or above the water surface. They grow in situations where the water level ranges from just below ground level to about half the maximum height of the plant. They differ in leaf shape, size and pint of attachment. Some of the weeds of this group have broad leaves, 5-50cm in diameter, and others have ling narrow leaves like grasses, less than 3-15cm or more in width; the latter are commonly called reeds. The leaves of emersed weeds do not rise and fall with water level as in the case of attached floating weeds. Some of the emersed weeds belong to the genera Nuphar, Nelumbo, Jussiaea, Myriophllum, etc.
3-MARGINAL WEEDS
Most marginal weeds are emersed weeds that can grow on saturated soil above the water surface; they grow from moist shoreline areas into water up to 60-90cm in depth. Marginal weed vary in size, shape and habitat species of this group are the most widely distributed rooted aquatic plant. Plants of this group are broad leaves herbs, shrubs, trees and some grasses. The important genera to which they belong are : Phragmitis, typha, Polygonum, Alternanthera, Populus, Tamarix, Cephalanthus, Juncus etc.
4-FLOATING WEEDS
Many water plants have leave that float on the water surface either singly or in rosettes .They have true root and leaves .Some are free floating and others rooted in bottom mud have floating leaves that rise or fall with the water level .They reproduce very rapidly under favorable conditions and are among the most troublesome of aquatic weed .Floating weed belong to the genera Eichhornia, Pistia, Salvinia , Lemna , Nymphaea and brasenia.
MAJOR AQUATIC WEEDS OF INDIA
Common Name Botanical Name
Water hyacinth Eichhornia crassipes
Cattails Typha angustata
Pond weed Potamogeton spp.
Hydrilla Hydrilla verticillata
Water lettuce Psitia stratiotes
Salvinia Salvinia molesta
Swamp morning glory Ipomea aquatic
Alligator weed Alternanthera spp.
Arrow head Sagittaria spp.
Spatter dock or Yellow lily Nuphar spp.
Pickerel weed Ponterdenia cordata
Reed weed Pharagmites communis
Swamp morning glory Ipomea aquatica
METHODS OF CONTROL OF AQUATIC WEEDS
Mechanical & Manual Methods
These methods employ physical forces to remove weeds:
1. Dredging- It is most common way of cleaning weeds in ponds and ditches.A dragline dredge may be equipped with a bucket or with a weed fork or other special tools. The bucket dreadge will also remove mud along with weeds while the weed fork will leave the mud. This method is labour expensive and slow.
2. Draining - Draining is an offseason weed management normally in drainage ditches by which weeds are cut manually or mechanically or spraying with a total weed killer or bottom ploughed to kill vegetative structures and root stock
3. Drying- Simple and inexpensive. The tops of under water weeds are exposed to sun by draining the water from ditches and ponds are allowed to dry. This method is effective in areas where the ponds are seasonal in use and remain dry during summers and rainy seasons. Drying is ineffective against emersed weeds and some of floating species.
4. Burning- It is used to control weeds in the banks above the water line. For obtaining the best results first searing the green vegetation and secondly after 10 -12 days with complete burning. In searing a hot flame is passed over the vegetation at such a rate that the plants wilt but are not charred. Mowing followed by burning the dried weeds may increase the effectiveness of mowing.
5. Chaining- This is relatively inexpensive method which is widely used. A heavy chain is attached between two tractors or teams on the opposite banks of ditch. As they move the chain drags over the weeds and breaks them off. Chaining is generally done only when the ditch is severely clogged. Chaining is primarily to ditches of uniform width and accessible from both sides with tractors. It is effective for cattails, tules, bur reed, arrow head and other emersed weeds.
The major disadvantages of chaining are its too laborious has to be repeated at regular intervals reverse chaining cannot be done.
6. Cutting- A mechanical weed cutter is used to cut the submersed weeds at 1 to 1.5 m deep in water. It consists of a sharp cutter bar operated hydraulically from a boat. The harvested weeds float to the water surface and removed manually or by sieve buckets.
Disadvantages of Mechanical Control Methods- They do not provide effective and economical weed control because of which repetitive operations are required. The weed fragment remaining proves as a source of new infestation.
HERBICIDES USED FOR CONTROLLING AQUATIC WEEDS
Asulam-Docks and bracken on banks.
Dalapon-Effective against grasses and cattails when applied on foliage. Draining of water before application is advisable. It is used in irrigation and drainage channels, lakes, ponds & ditch banks. Applied @ 15-20 Kg/ha for surface area. It is normally harmless to fish. However treated water is unsuitable for potable & irrigation purposes.
Dichlobenil-Effective on Elodea, watermilfoil, chara and potamageton species and is applied before weed starts growing. This is applied at the rate of 5 to 10 Kg/ha to the exposed bottom after draining water. This pre emergence application inhibits regeneration from roots and rhizomes. Water is let in after a month of treatment.
Diquat & Paraquat-These are generally used for control of floating weeds like water hyacinth and water lettuce with foliar application at 1 to 2 Kg/ha. There application in muddy water is ineffective. Efficiency is increased by combining with copper sulphate and triethanolamine.
Aqualin-The compound acrolein or acrylaldehyde has been named as aqualin. It is an active chemical attacks plant cells and kills them. It has lachrymatory effect on man and has to be sold by licensed operators.
Endothall-Aquatic weeds including algae without harming fish or aquatic life. It can be used for both submerged as well as emersed aquatic weeds. Granular formulation is Aquathall.
Copper sulphate-It is effective against many kinds of algae including chara and other species that causes scum. It is either applied as crystals or by placing crystals in a bag or towed behind a boat until the chemical is dissolved. This is applied at the rate of 0.5-1 ppm W. A concentration upto 2.5 ppm W is considered safe for human consumption while above 1 ppm W is considered unsafe for fish, but can be used for irrigation purpose.
Silvex-Effective for control of surface and emersed weeds like alligator weed, water lily, arrow head etc. prevalent in standing waters. Treated water is unsuitable for any purpose.
Method of application
Application is done by pumping the liquid into the water and allowing it to move as a blanket over and through the aquatic weeds. The herbicide may be introduced over a time period ranging from 45 min to 5 hrs. Temperature of water is important consideration. At 150C the dosage must be twice that at 28 0C. Hence the dosage must be adjusted with the plant population and temperature. In fast flowing streams, contact is not so thorough as in slow and hence, dosage must be increased when flow is greater than 10 cumec.
For proper control of weeds of wider water bodies power sprayers are mounted on motor boats. The spray range in this case will be 10 to 20 mts. With a discharge rate of 20 to 200 lts per min. For injection in stable water a hard pipe with several small holes is fitted. In flowing water the herbicide is injected from the shore itself. The herbicide is carried down the stream. During spraying the boats should maintain a speed of 2-5 Km/hr.
Biological control-
Name of Bioagent Weed controlled
Congo tilapia & Jawa tilapia Algae (chara & Nitella) & saw weeds (Najas)
Chinese grass carp or white amur
(Ctenopharyngodon idella) Aquatic plants
Common carp It is mud bottom feeder and it controls submersed aquatic weeds due to its uprooting plants and breaking up mats of algae in its search for food.
Marasmiellus inoderma Thread blight in water hyacinth
Flea beetles (Agasiches hydrophilla) Water hyacinth and Salvinia
Aquatic weed are those unwanted plants which grow in water and complete at least a part of their life cycle in water. Many aquatic plants are desirable since they may play temporarily a beneficial role in reducing agricultural, domestic and industrial pollution. Letting a crop of plants grow in a lake or pond and then killing it over a period of time, and consequently releasing nutrients back into the water, may help in fish production. However, many aquatic plans are considered weeds when they deprive human beings of all facets of efficient use of water and cause harmful effects, some of which are discussed below.
Submersed, immersed, emerged and marginal weeds in and along irrigation canals, ditches, and drainage channels impede water flow, increase evaporation, cause damage to canals and structures, and clog gates, siphons, valves, sprinkler heads bridge piers, pumps, etc.
Floating and deep-rooted submersed weeds interfere with navigation. Some of the tougher and densely growing weeds, e.g. water hyacinth and alligator weed become impenetrable and prevent boats and even steamers moving through. Submersed and floating aquatic weeds in farm ponds, village tanks and water reservoirs reduce their utility for water storage and irrigation.
Aquatic weed growth also prevents or impairs the use of inland waters for fishing. The weed assimilates large quantities of nutrients from water, thus reducing their availability for desirable planktonic algae. They cause oxygen deficiency and prevent gaseous exchange with atmosphere, resulting in an adverse effect on fish production. Excessive growth of these weeds may provide excessive cover, resulting in an overpopulation of small fish and interference with fish harvesting.
Aquatic weeds provide a suitable habitat for development of mosquitoes in impounded waters, causing malaria, filariasis and encephalitis. These weeds serve as the primary vector for the disease-causing organisms.
Aquatic weeds reduce the recreational values of lakes, tanks, streams, etc. as the water is made turbid or dirty with an undesirable odour
TYPES OF AQUATIC WEED
There are two types of aquatic plants: algae and hydrophytes.
ALGAE-Algae normally inhabit the surface of fresh and saline waters exposed to sunlight. While some kinds of algae are found in solid and on terrestrial surfaces exposed to air, the majority aquatic and adapted to live in ponds, lakes, reservoirs, steams, swimming pools and oceans.
Freshwater algae are of two types: planktonic and filamentous. planktonic algae, called phytoplankton, include the truly aquatic single-celled algae and the simplest filamentous or colonial forms. A heavy growth of algae may colour the water shades of green, yellow, red and black. Hey may also form water blooms or scums. They convert solar energy into food, remove CO2 from water during photosynthesis (in day time) and produce oxygen as a by product. During the night or in cloudy water, they release co2 in the water through respiration as consume O2.
Certain planktonic algae are beneficial as they can maintain biotic balance in natural aquatic environment because of their ability to produce oxygen and maintain an aerobic condition. They are the original sources of food for most fish and aquatic animals. Although planktonic algae are beneficial, their overabundance may be undesirable for many domestic and commercial water uses.
Excessive phytoplanktonic blooms often result in zooplanktonic (the microscopic animal forms) development that may deplete result in zooplanktonic the water of oxygen and lead to over fertilization or eutrophication and destruction of fish and other aquatic wild life. Dense growth of planktonic algae will shade bottom muds sufficiently to prevent germination of seeds and growth of many species of rooted submersed weeds, thus affecting the stability of the habitat
Generally, planktonic algae do not interfere with the use of surface waters or irrigation purposes. But some of them, the blue-green algae and green algae produce odours and scums that make unfit for swimming. Several of the blue-algae produce toxic substances that kill fish, birds and domestic animals.
Another group of algae called filametous algae (nanoplankton) consists of single celled joined end to end which may form single thread, branched filaments, nets, or erect stem like whorled branches or forked leaf like forms. They don’t have roots, stems or leaf as do higher plants. The important genera of the filamentous algae are: Chara, Nitella, Spirogyra, Hydrodictyon, Cladophora, Pithophora.
HYDROPHYTES-The hydrophytes, which represent more than 100 families, are vascular plants. They grow wholly or partially submersed in either fresh or saline water or in plaustrine areas. They are structurally different from mesophytes and xerophytes that grow in moisture-deficient situations. The protecting and conducting tissues of hydrophytes are less developed. They have extensive provision for aeration and buoyancy, particularly in the leaf mesophyll, ground tissue of the petiole and the cortex of the stem and root. Buoyancy is provided by aerenchyma or by air chambers. The air chambers may be either schiogenous or lysigenous, or both. Hydrophytes weeds can be grouped as submersed, emersed, marginal and floating weeds.
1- SUBMERSED WEEDS
Submersed weeds are mostly vascular plants the produce all or most of their vegetative growth beneath the water surface. Most submerged vascular weeds are seed plants and have true roots, stems and leaves. Abundance and density of these weeds is primarily dependent on depth and turbidity of water and physical characteristics of the bottom. A maximum depth of 3.5-4 m in clear waters is the limit for most of the submersed plants. They are capable of absorbing nutrients and herbicides through the leaves and stems as well as roots. They compete for nutrients with planktonic algae and decrease their production and a corresponding decrease in fish production.
The submersed weeds belong to the following genera: Potamogeton, Elodea, Myriophyllum, Ceratophyllum, Utricularia, Ranunculus, Heteratheral Alisma, Zannichellia, Lemna, etc.
2- EMERSED WEEDS
Emersed weeds are those plants rooted in the bottom muds with serial stems and leaves at or above the water surface. They grow in situations where the water level ranges from just below ground level to about half the maximum height of the plant. They differ in leaf shape, size and pint of attachment. Some of the weeds of this group have broad leaves, 5-50cm in diameter, and others have ling narrow leaves like grasses, less than 3-15cm or more in width; the latter are commonly called reeds. The leaves of emersed weeds do not rise and fall with water level as in the case of attached floating weeds. Some of the emersed weeds belong to the genera Nuphar, Nelumbo, Jussiaea, Myriophllum, etc.
3-MARGINAL WEEDS
Most marginal weeds are emersed weeds that can grow on saturated soil above the water surface; they grow from moist shoreline areas into water up to 60-90cm in depth. Marginal weed vary in size, shape and habitat species of this group are the most widely distributed rooted aquatic plant. Plants of this group are broad leaves herbs, shrubs, trees and some grasses. The important genera to which they belong are : Phragmitis, typha, Polygonum, Alternanthera, Populus, Tamarix, Cephalanthus, Juncus etc.
4-FLOATING WEEDS
Many water plants have leave that float on the water surface either singly or in rosettes .They have true root and leaves .Some are free floating and others rooted in bottom mud have floating leaves that rise or fall with the water level .They reproduce very rapidly under favorable conditions and are among the most troublesome of aquatic weed .Floating weed belong to the genera Eichhornia, Pistia, Salvinia , Lemna , Nymphaea and brasenia.
MAJOR AQUATIC WEEDS OF INDIA
Common Name Botanical Name
Water hyacinth Eichhornia crassipes
Cattails Typha angustata
Pond weed Potamogeton spp.
Hydrilla Hydrilla verticillata
Water lettuce Psitia stratiotes
Salvinia Salvinia molesta
Swamp morning glory Ipomea aquatic
Alligator weed Alternanthera spp.
Arrow head Sagittaria spp.
Spatter dock or Yellow lily Nuphar spp.
Pickerel weed Ponterdenia cordata
Reed weed Pharagmites communis
Swamp morning glory Ipomea aquatica
METHODS OF CONTROL OF AQUATIC WEEDS
Mechanical & Manual Methods
These methods employ physical forces to remove weeds:
1. Dredging- It is most common way of cleaning weeds in ponds and ditches.A dragline dredge may be equipped with a bucket or with a weed fork or other special tools. The bucket dreadge will also remove mud along with weeds while the weed fork will leave the mud. This method is labour expensive and slow.
2. Draining - Draining is an offseason weed management normally in drainage ditches by which weeds are cut manually or mechanically or spraying with a total weed killer or bottom ploughed to kill vegetative structures and root stock
3. Drying- Simple and inexpensive. The tops of under water weeds are exposed to sun by draining the water from ditches and ponds are allowed to dry. This method is effective in areas where the ponds are seasonal in use and remain dry during summers and rainy seasons. Drying is ineffective against emersed weeds and some of floating species.
4. Burning- It is used to control weeds in the banks above the water line. For obtaining the best results first searing the green vegetation and secondly after 10 -12 days with complete burning. In searing a hot flame is passed over the vegetation at such a rate that the plants wilt but are not charred. Mowing followed by burning the dried weeds may increase the effectiveness of mowing.
5. Chaining- This is relatively inexpensive method which is widely used. A heavy chain is attached between two tractors or teams on the opposite banks of ditch. As they move the chain drags over the weeds and breaks them off. Chaining is generally done only when the ditch is severely clogged. Chaining is primarily to ditches of uniform width and accessible from both sides with tractors. It is effective for cattails, tules, bur reed, arrow head and other emersed weeds.
The major disadvantages of chaining are its too laborious has to be repeated at regular intervals reverse chaining cannot be done.
6. Cutting- A mechanical weed cutter is used to cut the submersed weeds at 1 to 1.5 m deep in water. It consists of a sharp cutter bar operated hydraulically from a boat. The harvested weeds float to the water surface and removed manually or by sieve buckets.
Disadvantages of Mechanical Control Methods- They do not provide effective and economical weed control because of which repetitive operations are required. The weed fragment remaining proves as a source of new infestation.
HERBICIDES USED FOR CONTROLLING AQUATIC WEEDS
Asulam-Docks and bracken on banks.
Dalapon-Effective against grasses and cattails when applied on foliage. Draining of water before application is advisable. It is used in irrigation and drainage channels, lakes, ponds & ditch banks. Applied @ 15-20 Kg/ha for surface area. It is normally harmless to fish. However treated water is unsuitable for potable & irrigation purposes.
Dichlobenil-Effective on Elodea, watermilfoil, chara and potamageton species and is applied before weed starts growing. This is applied at the rate of 5 to 10 Kg/ha to the exposed bottom after draining water. This pre emergence application inhibits regeneration from roots and rhizomes. Water is let in after a month of treatment.
Diquat & Paraquat-These are generally used for control of floating weeds like water hyacinth and water lettuce with foliar application at 1 to 2 Kg/ha. There application in muddy water is ineffective. Efficiency is increased by combining with copper sulphate and triethanolamine.
Aqualin-The compound acrolein or acrylaldehyde has been named as aqualin. It is an active chemical attacks plant cells and kills them. It has lachrymatory effect on man and has to be sold by licensed operators.
Endothall-Aquatic weeds including algae without harming fish or aquatic life. It can be used for both submerged as well as emersed aquatic weeds. Granular formulation is Aquathall.
Copper sulphate-It is effective against many kinds of algae including chara and other species that causes scum. It is either applied as crystals or by placing crystals in a bag or towed behind a boat until the chemical is dissolved. This is applied at the rate of 0.5-1 ppm W. A concentration upto 2.5 ppm W is considered safe for human consumption while above 1 ppm W is considered unsafe for fish, but can be used for irrigation purpose.
Silvex-Effective for control of surface and emersed weeds like alligator weed, water lily, arrow head etc. prevalent in standing waters. Treated water is unsuitable for any purpose.
Method of application
Application is done by pumping the liquid into the water and allowing it to move as a blanket over and through the aquatic weeds. The herbicide may be introduced over a time period ranging from 45 min to 5 hrs. Temperature of water is important consideration. At 150C the dosage must be twice that at 28 0C. Hence the dosage must be adjusted with the plant population and temperature. In fast flowing streams, contact is not so thorough as in slow and hence, dosage must be increased when flow is greater than 10 cumec.
For proper control of weeds of wider water bodies power sprayers are mounted on motor boats. The spray range in this case will be 10 to 20 mts. With a discharge rate of 20 to 200 lts per min. For injection in stable water a hard pipe with several small holes is fitted. In flowing water the herbicide is injected from the shore itself. The herbicide is carried down the stream. During spraying the boats should maintain a speed of 2-5 Km/hr.
Biological control-
Name of Bioagent Weed controlled
Congo tilapia & Jawa tilapia Algae (chara & Nitella) & saw weeds (Najas)
Chinese grass carp or white amur
(Ctenopharyngodon idella) Aquatic plants
Common carp It is mud bottom feeder and it controls submersed aquatic weeds due to its uprooting plants and breaking up mats of algae in its search for food.
Marasmiellus inoderma Thread blight in water hyacinth
Flea beetles (Agasiches hydrophilla) Water hyacinth and Salvinia
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