Seed Production

Reference: Seed Production Techniques for Cereals and Millets by CIKS and RRAN. December 2013.

The best season for seed production is November – December. The pollination should not coincide with rains. Rains prevent quality and effective seed setting. The temperature of 37o c is favourable for seed setting. Method of seed production Sorghum is often a cross-pollinated crop and seeds are allowed to set by open-pollination in isolation. The crop should be raised in isolation of 200 metres for foundation and 100 metres for certified seed production to maintain the varietal purity. Time isolation is not permitted. The spacing between the plants should be 45 x 15 cm.

A webpage on sorghum, brief information on its production and nutrient by APEDA. Useful for CSOs, NGOs, trainers.

Seed production stages: Breeder seed --> Foundation seed --> Certified seed

Land selection

Land selection The land selected should be free from volunteer plants and wild grass varieties like Johnson grass, sudan grass and other forage types. The land should not be cultivated with the same crop in the previous season. Land should be fertile with good drainage facility.

An information bulletin on Rabi and Kharif Sorghum package of practises containing information on cropping system, preparation of land, selection of HYV and hybrid seeds, method and time of sowing, seed rate spacing and plant population, nutrient management, weed control, water management, insect, pest and disease management by IIMR. Useful for CSOs, NGOs, trainers.

Seed selection and sowing

Seeds used for the seed production should be of good quality certified seeds from an authentic source. Seeds should be healthy with good germination percentage. Seed rate is 3 kg/acre (7.5 kg/ha) for irrigated crop (transplanted) and for direct sown rainfed and irrigated are 6 kg/acre (15 kg/ha) and 4 kg/acre (10 kg/ha), respectively. In cultivation through transplantation, the duration of the crop is reduced by 10 days and the seed rate is also reduced by 1 kg/acre (2.5 kg/ha). For dryland or summer sowing, selected seeds should be hardened by soaking them in 1:0.6 volume of 1% Prosopis and Pongamia leaf extract and further pelleted with Pongamia leaf powder using 10% maida as the adhesive material. The seeds are sown in ridges and furrows at a depth of 2 - 4 cm along the sides of the ridges. The spacing between the plants should be 45 x 15 cm.

Nutrient management

Before final ploughing compost or farmyard manure @ 5 tonnes/acre (12.5 tonnes/ha) should be applied and ploughed into the soil. Instead of this cattle penning can also be practiced. 50 kg neem cake and 500 kg vermicompost per acre (125 kg neem cake and 1250 kg vermicompost per hectare) should be applied as basal manure. After first weeding at 20 – 25 days after sowing first top dressing should be done using enriched vermicompost (2 kg Azospirillum, 2 kg Phosphobacterium and 2 litres Panchagavya mixed with 250 kg vermicompost and kept covered for a week and then used) @ 250 kg/ acre (600 kg/ha) followed by the second top dressing at 40 – 45 days after sowing using 25 kg neem cake and 250 kg vermicompost per acre (60 kg neem cake and 600 kg vermicompost per hectare). During flower initiation stage 10% tender coconut solution (1 litre tender coconut water + 9 litres of water) should be sprayed. For rainfed crop, 50 kg pungam cake and 250 kg vermicompost should be applied as basal manure just before sowing. First top dressing should be done at 20 – 25 days after sowing using 250 kg/ acre of enriched vermicompost. At 40 – 45 days after sowing apply 25 kg pungam cake and 250 kg vermicompost per acre (60 kg pungam cake and 600 kg vermicompost per hectare) as second top dressing. Spray 10% tender coconut water at the time of flower initiation. All the above mentioned inputs should be applied to the rainfed crop only when the soil is wet.

Weed management

Sorghum is slow growing in the early stages and is adversely affected by weeds. Hence, the field should be maintained weed free upto 45 days. Hoe or hand weeding on the 10th day of transplanting is a must. Hoe or hand weeding between 30 – 35 days after transplanting and between 35 – 40 days for a direct sown crop is necessary.

Irrigation

The crop should be irrigated once a week to increase the percentage of seed setting. Irrigation during primordial initiation, vegetative, milky and maturity stages are very critical. When irrigation during critical stages are withheld that will result in poor seed setting and reduced size of the seeds.

Pest and disease management

Sorghum is affected by pests like shoot fly, stem borer, sorghum midge, ear head bug and diseases like kernel smut, head smut, downy mildew, rust and grain mold at different growth stages of the crop.

Roguing

Roguing should be done in the vegetative phase. Off-types and volunteer plants should be uprooted and removed before they start shedding pollen. Off-types are identified based on the plant height, leaf shape, leaf colour, stem pigmentation, days for flowering etc. Rogue other plants like Johnson grass, sudan grass, forage plants and diseased plants of kernel smut and head smut. Maximum percentage of off-types permitted at the final inspection is 0.01% for foundation seed production and 0.05% for certified seed production.

Field inspection

A minimum of three field inspections should be done between vegetative and harvesting stages by the Seed Certification Officer. First inspection is done during the vegetative stage to check isolation requirement, off-types, volunteer plants and diseased plants. Second inspection is done during the flowering stage to check off-types, isolation and other relevant factors. The third inspection should be scheduled at the time of maturity prior to harvest to check for designated diseases, true nature of plants, head and seed.

Harvesting

Seeds attain physiological maturity 40 – 45 days after 50% flowering. A black layer formed over the seeds is a sign to confirm the physiological maturation of the seeds. After confirming the maturity the earheads should be harvested. At this time the moisture content would be around 20 – 25%.

Threshing and processing

Harvested earheads should be dried further for a safe moisture level of 15 – 18% before threshing. After drying, the earheads are beaten with bamboo stick to separate the seeds. In case of mechanical thresher care should be taken to prevent the seeds from mechanical damage. Threshed grains are winnowed and cleaned. Cleaned seeds are further dried to attain a safe moisture content of 8% and graded using round perforated metal sieve of 9/64” size as middle sieve.

Drying and storage

The cleaned and graded seeds are dried to attain 8% of moisture content under the sun. Seeds can be stored upto 12 months under open storage conditions and upto 18 months in moisture vapour proof containers.

Seed standards

The percentage of maximum physical purity of certified and foundation seeds should be 98% with a minimum of 75% of germination capacity and 8 - 13% of moisture content. The presence of inert matter and huskless seeds should not exceed 2.0% and other distinguishable varieties and weed seeds should not be more than 10/kg for foundation and 20/kg for certified seeds.