Seed :: Pulses :: Soyabeans

QUALITY SEED PRODUCTION IN SOYABEAN

 

Selection of land

The selection of land is the first and foremost step for a seed producer. It should be selected carefully. Selection of fertile and healthy seed plot will certainly help in the production of quality seed. The field must not have been sown with soyabean in the previous season. This is done to avoid volunteer plants that cause admixture. Fields continuously cultivated with soybean may harbour wilt pathogen. Hence, such fields must be avoided wherever possible. Follow the crop rotation will help to reduce endemic pathogen. .
Soil with neutral pH must be selected. Loam or 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 andphysically 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. Soyabean is a self pollinated crop and must be grown 3 m (15 feet) away from another variety of soyabean.     

Frequently we come across seed farmers complaining that they are not able to isolate seed crop. Under such condi­tion five rows of maize can be raised all around 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 only with this idea in mind. In Tamil Nadu the best seed crop is grown during June - July and September - October, so that the seeds mature during the cooler months of January - February.

Preparation of land

The land is made into ridges and furrows of one feet wide or beds and channels of 4' x 6' depending on cultivation practices.

Fertilizer

Ten cartloads (5T) of well decomposed compost is spread along with basal application of 40 kg urea: 360 kg super phosphate and 50 kg muriate of potash 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 for a good field stand. Hard seeds, diseased seeds, immature seeds, off coloured seeds that are green, brown, purple, shrunken and deformed seeds must be removed.   

Attention

It must be noted that any farmer can take up certified seed production. The Agricultural Officer of that area will be of help. The certified seed crop will be taken using Foundation seed and Foundation seed crop using Breeder seeds.

Seed rate

Depending on the variety, the seed rate varies from 16kg per acre.

Seed treatment

Before sowing, the shrunken, shrivelled, fungal infected and bruchid infected seeds must be removed and only good seeds must be sown. To control seed borne diseases, seeds can be treated with carbendazim fungi­cide @ 4g kg-l of seed.


Deformed seed and good seed

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.
Pulses are protein rich crop. In order to produce protein, the crop plants must be healthy and vigorous. Seed crop must be more vigorous in order to produce quality seeds. Some times, minor nutrients may not be available in the seed plot leading to production of poor quality seeds. To overcome this shortage of nutrients, the seeds can be soaked in nutrient solutions before sowing. Similarly seeds can be soaked in nutrients solutions that help them to germinate faster even in low amounts of water and withstand drought

 

Moist sand hydration

For sowing one acre of seeds we need 16kg of soyabean seeds. The seeds have to be soaked in water. But soaking directly in water injures the seed. This is due to the fact, that the high protein content of seed (42%) leads to faster absorption of water which is not regulated by seed coat and hence the seed coat is damaged. Such type of damage is called imbibition damage. Imbibition damaged seeds have poor germination and vigor leading to large gaps in field. Hence, instead of soaking the seed directly in water, soybean seeds are hydrated using moist sand.
        
Take 16 kg of sand to which 800 ml of water is added to achieve 5% moist sand. The seed to be sown are then placed in alternate layers of seed and sand in plastic bucket, covered with a gunny and placed under shade or cool place for seed to get hydrated. After 16hrs the seed is separated from sand by sieving.

Seed treatment using rhizobium

Rhizobium are small bacteria that live inside the roots of soyabean and similar legumes. These bacteria get into the roots of legumes and form small round structures called nodules . A plant root may have more than 50-100 nodules depending on the population of the bacteria in the soil. These bacteria fix atmospheric nitrogen and make it available to the plant roots. The plant inturn provides food to the bacteria and protects them by forming a thick layer of plant skin. This relationship between bacteria and plant is known as symbiotic relationship. Soyabean plant thus inoculated can fix upto 210 kg Nitrogen per acre.


Rhizobium packet and treated seed & Rhizobium treated seed

Since, the soil mayor may not possess native rhizobial population, it is necessary to add rhizobia to the seed before sowing. This is done using rhizobial packets by a process called inoculation. The rhizobial packets are nothing but, bacterial suspension mixed in peat soil. The packets are avail­able in 250g.
Rhizobial inoculation is a simple treatment that farm women can take up while men are busy preparing the field for sowing.

How to treat seeds using rhizobium packets?

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 g of rice to 500 ml of water and boiled until the rice becomes sticky. Three hundred milliliters of rice gruel is needed for preparing the rhizobial inoculation. The prepared rice gruel is then cooled under shade for 5 hrs. To this cooled rice gruel, two packets of rhizobium are added and stirred into a black sticky mass. The 16 kg of Soyabean seeds are placed in bucket. The rice gruel-rhizobial mixture is then poured over the seed and seeds are mixed well using a stick or hand. After assuring that all the soyabean 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.     

Caution

  • Always buy freshly prepared packets.
  • Seed treatment using fungicides must be done 24 hrs earlier to rhizobium seed treatment.
  • Do not use the rhizobium packet if the content is dried.

Phosphobacteria seed treatment

Being a highly nutritious crop, soyabean needs huge amount of phos­phorous for its growth and development. Just like we add Rhizobium  we can also add phosphobacteria which can perform the job of solublizing the phosphorous in the soil and provide it to the plant. As mentioned for rhizobium, phosphobacteria is also sold in 250g packets. Two such packets are sufficient to treat the seeds of an acre. The method of seed treatment is similar to that of rhizobium.

Sowing

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

Irrigation management

Seed crop is very sensitive to irrigation. Seed fields must be constantly monitored for drought conditions. If not irrigated properly, pulse crop shed flowers. Water starved plants produce seeds that are hard and small with low vigor. Hence, pulse seed crop needs regular and sufficient irrigation.
Water is applied 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 feeding 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 nutrients 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 DAP nutrient solution for spraying. This is done by soaking 4 kg of DAP fertilizer in 20 litres of water overnight. The next day morning, the solution is filtered through a cloth. One litre of filterate is then added to the sprayer tank followed by adding 9litres of water to fill the tank. The solution is then sprayed during the early morning or evening to avoid scorching. The crop must be irrigated immediately after spraying. This nutrient solution is sprayed 25-35 days after sowing followed by another spray at 40-50 days.
Apart from DAP, soybean plant may show symptoms of Zinc deficiency where, young leaves show yellowing symptoms. Under such conditions, spray the plants with500g of Zinc sulphate dissolved in 100 litre of water. 

Precautions during spraying

  • Irrigate the crop immediately after spraying or ensure that adequate soil   moisture is available.
  • Spraying should be done during evening hours.
  • Wet well the crop with spray solution.
  • DAP solution can be combined with pesticides.
  • Avoid spraying during peak flowering.

Weed control

Immediately after sowing and irrigation, Basalin weedicide is sprayed by dissolving 2 ml per liter 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 after 15 days will be useful. Sometimes, the 600 ml of Basalin can be mixed with 20kg sand (4 iron chatties of sand) and evenly spread on the field within three days of sowing. This reduces the cost of spraying.

Pest and disease control

Pests

In the initial stages, stem fly affects the crop leading to death of terminal shoots. The major pest is heliothis which makes holes in young pods and eats the seeds. The worms can be collected and killed or sprayed with Methyl dematon, Dimethoate or Phosphomidan at the rate of 2 ml per litre.
                                               
Diseases

During the growing phases of the seed crop incidence of wilt being noticed. The affected plants turn brown and die. These plants can be rogued out as and when they appear. The affected area is sprayed using 0.1 % Bavistin solution. Powdery mildew is noticed by the presence of white powder deposits on the leaves. The Powdery mildew can be controlled by spraying Dithane M 45 @ 4g / litre.    

How to prepare 0.1% and 1% Bavistin solution?

Take one grams of Bavistin and dissolve it in one litre of water for preparing 0.1 % solution and ten grams of Bavistin is dis­solved in one litre to get 1 % solution

Maintaining seed quality by through roguing

One of the most important aspects of seed production is thorough roguing. Rogue is defined as presence of those plants that deviates from the characters described for the variety. Such rogues if left in the field they tend to reduce the genetic purity of the seed crop and thus reduce purchase value of resultant seed. Roguing is defined as the operation of removing rouges. 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 rouging operation.

When to do rouging?

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

Roguing during vegetative stage

During vegetative stage i.e. during first 25 days, rouging is attempted based on plant characters like height of plant, leaf shape, size, venation, surface of leaf and presence or absence of hairs on plant surface. Plants showing wilt and yellow mosaic are also removed and the crop is immediately sprayed with Rogor (2 ml/lit) for controlling white fly that spreads the yellow mosaic disease.

Roguing during flowering stage

The rouges are identified based on flower characteristics. The varieties grown in Tamil Nadu are purple coloured flowers. Those with white flowers must be removed. During this phase when most of the plants are flowering, all those plants still in vegetative stage are also removed.

Roguing during pod formation stage

At this phase, the rouges are removed based on pod characteristics like length of pod, size, shape, number of seeds per pod and hairiness.


 Soybean pod

Roguing during pod harvest phase

Roguing is done prior to harvest based on seed characteristics like colour of seed, lustre and size of seed. Certain wild soyabean types are black coloured ( kali tur) and must be removed.

Soybean harvesting stage
      
Attention

Varietal characteristics for various crops are given at the end to this lesson.

Caution!

All the rouges must be immediately removed from the seed field and destroyed

Care during harvest

The seed crop comes to harvest 85-90 days after sowing, this is generally 30 days from 50% flowering. At this time, 70% the pods turn yellow and few at the base turn brown coloured. Most of the basal leaves have dropped and rests are yellow coloured. Prior to harvest there is an important pest to be controlled. Bruchids are the major pests of stored 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 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 (2 ml of insecticide per litre) ten days prior to harvest.

The indication mentioned above is the right stage of harvest for seed purpose. Delay in harvest will lead to shattering of pods and infection by diseases, pests and sometimes seed vigor will be lost due to untimely rains.
          
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 brown 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.

Cleaned seeds are then dried on tarpaulin or on the threshing floor until the moisture content is reduced to 12%. 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. Depending on the size of soyabean variety, the sieve size for soyabean is 8.00mm. After sieving, those seeds that are broken, fungal infected, seed coat damaged are removed.


Sieving seeds

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. In this section we will learn about the role of seed moisture content, seed treatment and proper methods of storage for prolonging seed viability.

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 moisture are attacked by fungal and other storage pests like bruchids. Further, seeds being living organisms 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 12% for short term storage of 6-8 months. Seeds with 12 % moisture can be stored in cloth or gunny bag. Seeds that have to be stored for long term i.e. 1-2 yrs, have to be dried to 7% moisture. Such seeds have to be stored in 700 gauge polythene bag.

Point to remember

Seeds stored in polythene bag have to be dried to moisture content below 7%. This is necessary because polythene bag do not allow moisture to move out and seeds if stored with high moisture will get damaged. Hence always store seeds in polythene bags with low moisture.

Seed treatment

Seeds are generally affected by fungi during storage. To prevent, seeds are treated with fungicide before storage. Soyabean seeds are treated using Bavistin at the rate of 4 g/kg 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. 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.
           
Seeds are to be stored without any detrimental effect to vigor. Incase of short term storage, cloth bag can be preferred. Cloth bag is porous and hence it can hold seeds for short period. However, cloth bags are cheaper and easily made using local tailor. Large quantity of seeds can stored in gunny bag. If the seeds are to be stored for longer period that thick polythene bags can be used

Stacking seed bags

Seed bags can be stacked one upon other upto six bags. 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.

Taking care of seeds during storage

Seed treatment is most effective in combating fungal pathogens.

Grain cum seed storage

Pulses are used both as seed and grain. Pulse seeds have high demand as grain also. Farmers may be tempted to use them for grain as the market price for grain sometimes exceeds the seed cost. Under such circumstances the seeds can treated with harmless substances like activated clay, neem oil and vegetable oil.

What is activated clay?

Activated clay is ordinary white clay moisture removed 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.

Activated clay is used to treat seeds at the rate of 100g per kg of seeds. Activated clay has rough clay particles that cut the surface of bruchids. Such bruchid beetles then die as they loose moisture fast compared to unbruised ones.
Similarly pulse seeds can also treated using vegetable oils/neem oil @ 3 m1 per kg. These techniques are eco- friendly techniques which do not harm the environment also.

Seed certification
           
Seed certification guarantees the quality of seed as it ensures that the certified seed has the genetic, physical, physiological and seed health qualities.  Genetic purity means that the seed gives rise to a plant which conforms to the varietal characteristics of the variety. The physical purity means that the seed is free from stones, broken seeds, straw bits and leaf bits etc. Physiological quality is measured by germination and seed health envisages freedom from pest and diseases.
           
Seed certification is being done in many stages. It starts from verifying whether seeds were obtained from authenticated source, verification of isolation distance and inspection during plant growth, flowering, harvesting, processing and bagging. Also seed samples are drawn form the seed lot and sent to seed testing lab to test whether the seeds are possessing required physical purity and germination. Then certification tag is issued. Colour of the tag is blue for certified seeds.
           
Only those seeds harvested from fields having prescribed field standards and possessing required seed standards are certified by the Certification Agency. Seeds thus certified are offered for sales. For further details nearer seed certification office may be contacted.

Minimum seed certification standards prescribed for certified seed

Field standards

Maximum permitted (%)

 

Foundation

Certified

Rogues

 

 

 

0.10

0.50

Seed standards

Factors

Standards for each class

 

Foundation

Certified

Pure seeds ( minimum)

98.0%

98.0%

Inert matter ( maximum)

2.0%

2.0%

Other crop seeds

 

 

(maximum)

None

10/kg

Weed seeds (maximum)

5/kg

10/kg

Other Distinguishable varieties

5/kg

10/kg

Germination (minimum)

70%

70%

Moisture content (maximum)

12.0%

12.0%

Vapour proof containers

 

 

(maximum)

7.0%

7.0%

Characteristics of cultivated varieties that can used while rouging

(Plants possessing characters other than given for a variety must be removed)

Characteristics

CO 1

CO2

Parents

Pure line selection from
Taiwan variety

UGM 21xJS 335
selection from

Duration of 50% flowering (days)

37

30-40

Duration (Days)

85

75-80

Plant height (cm)

58

30-40

No. of branches

6

 

Colour of flower

Purple

Pink to purple

No. of seed per pod

2-4

 

Seed colour

Buff yellow

Cream to yellow

100 seed weight (gm)

12.5

13-14

Seed yield (kg/ha)

1640

1340

 
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