Seed :: Pulses :: Greengram

QUALITY SEED PRODUCTION IN GREEN GRAM

 

Selection of land for seed production
           
The seed production plot must be selected carefully. A fertile and healthy seed plot will certainly produce quality seed. The field selected for seed production must not have been sown with green gram in the previous season. This is done to avoid volunteer plants that cause admixture. Fields continuously cultivated with green gram may harbor root rot or wilt pathogen. Hence, such fields must be avoided where ever possible. Following the crop rotation will help to reduce endemic pathogen.
           
Soils with neutral pH must be selected. Loam of clay loam soils are best suited. Higher organic matter will lead to production of vigorous seed.

Isolating the seed crop to avoid genetic contamination
           
The quality seed must be genetically and physically pure. Genetic purity can be maintained by preventing cross pollination with other undesirable varieties. This is achieved by isolating the seed crop.
           
Isolation is the act of growing the seed crop away from a contaminant such that cross pollination is prevented. The greengram seed crop must be grown 5 m (15 feet) away from another variety of greengram. To prevent contamination 5-6 rows of the same crop may be sown as a border crop.

Frequently we come across seed farmers complaining that they are not able to isolate the seed crop. Under such condition five rows of Maize can be raised all around the seed crop to prevent contamination.

Selecting the right season
           
Seed is very sensitive to weather. A grain crop can be sold for a lower price even if it is damaged by rain. But a seed crop, if affected will lead to reduced seed vigor. Hence selecting the right season is necessary. Generally, the seed should mature in cool dry climate. Seasons are selected with this idea in mind. In Tamil Nadu the best seed crop growing season is June – September and February – March.

Preparation of land
           
The land is thrown in to ridges and furrows of one feet wide or beds and channels depending on cultivation practices.

Fertilizer
           
Ten cartloads (5t) of well decomposed compost is spread along with basal application of 20 kg urea and 120 kg super phosphate per acre.

Selection of seeds
           
Seeds used for sowing must be from an authentic source. An authentic source is one that proves the genetic purity and other aspects of seed quality of seed being sown. Seeds used for sowing must also be vigorous, only then you can expect a good field stand. Seeds must be checked for hard seeds, diseased seeds, immature seeds, shrunken, deformed and off coloured seeds.

Selected seeds
C. Good seeds D. Deformed seeds

Seed rate
           
Depending on the variety the seed rate varies from 8-10 kg per acre.

Seed treatment
           
Before sowing, shrunken, shriveled, fungal infested and bruchid infected seeds must be removed and only good seeds must be sown. Some times hard seeds occur in some varieties due to initial dormancy. Such variety seeds must be identified and treated with commercial sulphuric acid.

Seed hardening
           
Pulses are generally grown as rainfed and some times the seed crop even though not recommended as a rainfed crop may experience drought situations. Plants can be hardened by providing certain nutrients and hormones that help the plants to fight of disease and sustain vigor during stress conditions.

How to harden Greengram seeds?
           
For sowing one acre of seeds we need 8 kg of greengram seeds. These seeds must be soaked in four litres 0.01% manganese sulphate nutrient solution for three hours. After soaking them for 4 hours, the solution is drained and the seeds are spread over a gunny and dried under shade for 8 hours.
           
Preconditioned seeds are soaked in botanical leaf extracts of prosopis (Prosopis juliflora) and pungam (Pongamia pinnata) using 1% solution and taken in 1:1 ratio or mixed in 1:1 ratio. One kilo of seed is soaked in 300 ml of solution. So, for eight kilos we need 2.4 lit of solution in which seeds are soaked for three hours.

Seed treatment using Rhizobium
           
Two packets of Rhizobium will be needed to treat seeds of an acre. In order to make the rhizobium stick to the seeds, we need a binder. The binder is prepared using rice gruel. This is prepared by adding 100 gm of rice to 500 ml of water and boiled until the rice becomes sticky. Three hundred milliliters of rice gruel is cooled under shade for 5 hrs. To this cooled rice gruel, two packets of rhizobium are added and stirred into a black sticky mass. Eight kilos of greengram seeds needed for an acre are placed in a bucket. The rice gruel-rhizobial mixture is then poured over the seed and mixed well using a stick or hand.  After assuring that the greengram seeds are coated evenly by rhizobial inoculum, the seeds are spread over gunny and dried under shade for 6 hrs. The dried seeds are then used for sowing within 24 hrs of inoculation.

Seed treatment using fungicide
           
Seeds must be treated with seed treating fungicide to reduce infection by fungal pathogens found in the soil. Black gram seeds are treated with Bavistin 2 g for every kilo of seeds. Now-a-days bio remedies like Trichoderma viridi is recommended for pulses at the rate of 4g per kilo of seed.

Sowing
           
The seeds are sown at 2 cm depth with a plant – to – plant spacing of 10 cm and 30 cm between rows.

Emerging green gram seed crop

Irrigation management
           
Greengram sown field should be irrigated immediately after sowing followed by life irrigation on the third day. Then, irrigation is carried out whenever, the fields become dry. Irrigation during flowering, pod formation and seed development are must.

Foliar application of fertilizers
           
Some times, basal application of fertilizers alone is not sufficient for the seed crop. It is necessary to provide nutrition during the heavy growth and seed formation period when there is a huge demand for nutrients.
           
The nutrient needed by the fastly developing pulse seeds are provided through foliar feeding. This provides rapid food source like sick human are provided glucose fluid through intravenous method. We have to prepare a nutrient solution for spraying. This is done by soaking the following chemicals in water (100 litres). This nutrient solution is sprayed 25-35 days after sowing followed by another spray 40-50 days after sowing.

Chemicals / Fertilizers

Quantity to be soaked in 100 L

1. Urea

4.0

2. D.A.P.

1.0

3. Muriate of Potash

0.6

4. Potassium sulphate

0.02

5. Succinic acid

0.02

6. Teepol

0.04 ml

Weed control
           
Immediately after sowing and irrigation, Basalin weedicide is sprayed by dissolving 2 ml of Basalin per litre of water. The spraying of weedicide must be done within three days of sowing. If done later, it can harm the seed crop. Application of weedicide will control the early growing weeds, in order to control later emerging weeds, manual weeding done 30 days after sowing will be useful.

Pest and disease control

Pests
           
In most part of the areas, the incidence of stem fly is very high. This pest affects the plant at the early stages leading to drying and withering of affected plants. During the growth phase major pests like aphids, leaf hopper, white fly affect the seed crop. These pests can be controlled by spraying either Mehyldematan, Dimethoate or Phosphomidan at the rate of 2 ml per litre.

Diseases
           
During the growth phases of the seed crop incidence of yellow mosaic can be seen. The affected plants show yellow mottled symptoms. These plants can be rogued out as and when they appear. White fly is known to spread this disease, hence after removal of the affected plants, it is followed by an insecticide spray as mentioned above. Leaf crinkle and leaf curl diseases are also found to affect the crop. Such plants have to be rogued. Apart from this, greengram is also affected by root rot, wilt which have to be removed and the affected area can be sprayed with 0.1% Bavistin solution. Rarely the seed crop is affected by Cercospora leaf spot which can be distinguished by the presence of brown spots. Powdery mildew is noticed by the presence of white powder deposits on the leaves. The Cercospora and Powdery mildew can be controlled by spraying 1% Bavistin solution. Root rot is also noticed when plants suddenly wilt and the base of the stem shows brown lesions.

 Maintaining seed quality by thorough roughing
           
One of the most important aspects of seed production is thorough rouging. Rogue is defined as the presence of those plants that deviate from the characters described for the variety. Such rogues if left in the field they tend to reduce purchase value of resultant seed. Roguing is defined as the operation of removing rogues. In practice, all plants that do not obey the characteristics of the particular seed crop are to be removed along with diseased plants, other crop plants, weeds, insect affected plants during roguing operation.

When to do roguing?
           
Roguing is more effective if done prior to flowering, since upon flowering there is very high possibility of cross pollination. Though greengram is self pollinated, some extent of cross pollination is caused by bees. Roguing is also attempted during flowering, pod formation stage and prior to harvest in case of pulse crop.

Roguing during vegetative phase
           
During vegetative phase i.e., during first 25 days, rouging is attempted based on plant characters like height of plant, leaf shape, size, venation and presence or absence of hairs on plant surface. Plants showing tendril formation and those showing symptoms of root rot, wilt and yellow mosaic are also removed.

Roguing during flowering stage
           
The rogues are identified based on flower characteristics.  During this phase when most of the plants are flowering, all those plants still in vegetative phase are also removed and those that flower too early also to be removed.

Roguing during pod formation stage
           
At this phase, the rogues are removed based on pod characteristics like length of pod, pod width, shape of tip, colour of pod (green, red, blotched).

Roguing during pod formation stage
           
At this phase, the rogues are removed based on pod characteristics like length of pod, size, shape, colour of suture, presence or absence of bend at pod tip.

Roguing during pod harvest stage
           
Roguing is done prior to harvest based on seed characteristics like colour of seed, luster and size of seed.

Causion
       
All the rogues must be immediately removed from the seed field and destroyed.

Roguing

Proper care during harvest
           
The seed crop comes to harvest 55-65 days after sowing and it varies according to the varieties, this is generally 30 days from 50% flowering. At this time, the pods turn brown to black from green. Prior to harvest there is an important pest to be controlled, Bruchids are the major pests of stored pulse seeds.

Pre-harvest sanitation spray
           
Bruchids lay eggs on the surface, the grubs bore into the seeds and eat the cotyledon. Those seeds store poorly and loose their viability faster. It has been found that bruchids lay their eggs on the pods while in the field itself. Hence control of these pests must start from the field itself. The field carry-over of Bruchids can be controlled if the crop is sprayed using Quinalphos 25% EC (2 ml of insecticide per litre) ten days prior to harvest.

Harvesting
           
Upon ripening, the greengram pods will turn from green to yellow to black. This is the right stage for harvest for seed purpose. Delay in harvest will lead to shattering of pods and infection by diseases, pests and some times seeds vigor will be lost due to untimely rains.

Delay lead t pod shattering
           
In case of irrigated crop, the ripened pods can be collected in one or two pickings and dried on the threshing floor. If the plants come to even harvest, then the plants are cut and spread over the threshing floor to dry. The plants will dry and become black and pods may start splitting. The plants are then beaten using pliable sticks to prevent damage to seeds. After thorough beating, the seeds are separated from pods. The plant debris are removed and seeds cleaned by winnowing.

Cleaning seeds

Cleaned seeds are then dried on tarpaulin on the threshing floor until the moisture content is reduced to 10%. This is the safe moisture content for storing seeds and maintaining their viability.

Processing to improve seed quality
           
One of the main characteristics of seed quality is the right size. Plumpy seeds are better than ill-filled puny seeds. Grading is one simple method by which we can separate the filled seeds from broken and puny seeds. Grading is done using round holed sieves. Such sieves are easily available in the market at an average price of Rs.50/- depending on the size of greengram variety, the sieve size for greengram is 2.36 mm. After sieving, those seeds that are broken, fungal infected, seed coat damaged seeds are removed.

 Protecting seeds during storage
           
Seeds after harvest have to be stored so that they are viable and healthy for sowing during the ensuing season. Hence, proper after care during storage is very essential part of seed production.

Seed moisture content
           
Seed moisture is the most important physical quality. Seed moisture determines the length of seed storage life. Higher the moisture, the longevity of seed is reduced drastically. Seeds with high moisture are attacked by fungal and other storage pests like Bruchids. Further, seeds being living organism tend to utilize all their stored energy and loose vigor. Hence, reducing seed moisture is the first step in ensuring longer seed life.
           
The moisture content must be reduced to 9% for short term storage of 6-8 months. Seeds with 9% moisture can be stored in cloth bag or gunny. Seeds that have to be stored for long term i.e. 1-2 yrs, have to be dried to 8% moisture. Such seeds have to be stored in polythene bag.

Seed treatment
           
Seeds are generally affected by fungi during storage. To prevent, seeds are treated with fungicide before storage. Greengram seeds are treated using Bavistin at the rate of 2 g/kilo of seeds.

Seed packing
           
After seed treatment, seeds have to be stored in bags or containers. Choosing the right type of container is necessary. This depends on the quantity of seeds to be stored and storage environment. We already know that seeds absorb moisture and even if the seed is dried to safe moisture content before storage, during storage depending upon the prevailing climatic conditions, seeds tend to absorb moisture. If the storage is attempted in an environment with high humidity, seed absorb moisture until they equilibrate with the atmosphere. Hence high humidity in the environment will lead to increase in seed moisture that is detrimental to seed storage. Such high humid conditions exist at sea shores, near lakes and rivers. Most of the places of peninsular India are highly humid especially during the monsoon periods between the months of June-December.
           
In case of short term storage, cloth bag can be preferred. Cloth bag is porous and hence it can hold seeds for short period only. However, cloth bags are cheaper and easily made using local tailor. Large quantity of seeds can be stored in gunny bag. If the seeds are to be stored for longer period, thick polythene bags can be used.

Stacking seed bags
           
Seed bags can be stacked one upon other upto 6 layers. Stacking beyond this will damage the seeds present in the lower layers. To prevent damage to seeds in the bottom layers, the layers can be rotated periodically by shifting the lower layers to the top and vice-versa. Stacking must also be done on dunnages. Dunnages are wooden rafts that keep the seeds above floor and allow aeration. Tarpaulins and thick plastic sheet can also be used.

Grain cum pulse seed storage
           
Pulses are both as seed and grain. Being of high protein value, pulse seeds have high demand as grain also. Farmers may be tempted to use them for grain as the market price for grain some times exceeds the seed cost. Under such circumstances the seeds can be treated with harmless substances like activated clay, neem oil and vegetable oil.

What is activated clay?
           
Activated clay is ordinary white clay removed of moisture and acid washed to improve its ability to damage insect surface. It is very cheap and non-toxic to humans. Seeds treated with activated clay can be washed and reused for consumption, at the same time it offers protection against bruchid infection.
           
Activated clay is used to treat seeds at the rate of 100 g per kilo of seeds. Activated clay has rough clay particles that cut the surface of bruchids. Such beetles then die as they loose moisture fast compared to unbruised ones.
Similarly pulse seeds can also treated using vegetable oils/ neem oil at 3 ml per kilo. These techniques are farmer friendly techniques and do not harm the environment.

Seed certification
           
Seed certification guarantees the quality of seed as it ensures that the certified seed has the genetical, physical, physiological and seed health qualities. By genetical quality we mean that the seed has all the characteristics as desired by the breeder who had developed the variety, like short duration, higher yield, high protein etc. The physical quality entitles the seed to be free of stones, broken seeds, straw bits, leaf bits and low seed moisture for safe storage. Physiological quality is measured by germination and seed health envisages freedom from pest and diseases. Only those seeds that possess the aforementioned qualities alone are certified by the certification agency.
           
The certification agency officials visit the seed field for quality inspection and only those seed fields that are maintained properly are alone accepted for certification. The accepted fields are then harvested and processed under the supervision of the certification agency and tested for germination and other seed quality in the lab.
           
Only those seeds that possess the required quality are given certificate known as tag. The tag is blue in colour. So, next time when you buy a seed see if it has the blue tag.

Minimum seed certification standards prescribed for certified seed

Field standards

 

Rogues (maximum limit)

0.2%

Seed Standards

 

Pure seeds (minimum limit)

98.0%

Inert matter (maximum limit)

2.0%

Other crop seeds (maximum limit)

1.0%

Weed seeds (maximum limit)

1.0%

Germination (minimum limit)

75.0%

Moisture content

 

Moisture proof bag

8.0%

Moisture previous bag

9.0%

 
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