Best Management Practices for Sali season in Transplanted Rice in Assam

Varieties

The high yielding long-duration varieties such as Swarna-Sub1, Ranjit-Sub1 and Bahadur-Sub1, are able to tolerate complete submergence for two weeks. Depending on flood-water quality, the submergence-tolerance period may vary. Turbidity of water hinders radiation to reach plants, thereby impacts the photosynthesis process in plants. BINA Dhan 11, a medium-duration submergence-tolerant rice variety could be grown in all Assam districts including the areas having low rainfall, and under delayed post-flood sowing conditions mostly prevalent in upper Brahmaputra valley zone. The varieties for different growing situations are listed below along with their brief characteristics description.

Seed quality and treatment

Seed quality: Quality seed is clean (contains no pebbles, soil particles, weed seeds), genetically pure (contains only grains of one variety) and healthy (well filled, of the same color, without cracks, and no obvious disease- or pest-damage).

Seed selection: Seeds are immersed in plain water and stirred well. Seeds, those sink down are selected, and those float are rejected.

Seed treatment: Adopt seed treatment with recommended fungicides only. Once the selection process is done, the seeds should be soaked directly in one of the following fungicidal suspensions for 12 hours. One liter of fungicidal solution is required to treat one kg of seed. Treated seeds should be kept in incubation for 48-72 hours.

Safety precaution: Plastic gloves should be used while handling chemicals to avoid ill- effect on health

Nursery raising

Time of sowing: Last week of May to the first week of June is the most appropriate time for raising a nursery.

Seed rate: 40 kg per hectare

Nursery size: For one hectare of the main field, the nursery seedbed size should vary between 750 and 1000 m2, but should not be more than 1/10thof the main field size. Land is thoroughly puddled and seedbeds of 10 m length, 15 cm height and 1.5 m breadth are prepared keeping a 60-cm gap in between the beds. The length of the bed may vary according to convenience and availability of space.

Irrigation: Irrigate to maintain saturated condition in the surface soil of the seedbeds. Maintain 2-3-cm standing water 2-3 days prior to uprooting.

Plant protection: Adopt plant protection measures in the standing nursery as per standard package of practices.

Seedling priming against insects: As protective measure against stem borer, gall midge and hoppers, the uprooted seedlings are washed and the root portion is dipped in 0.02% solution of Chlorpyriphos (2 ml/lit of water) along with 1% urea (10g/liter of water) for 3 hours. Alternatively, spray Chlorpyriphos 20 EC @ 0.02% in the standing nursery 5-7 days before uprooting.

Nursery fertilizer: Use 3-1-2 g N-P₂O₅-K₂O + 2 kg manure per m² i.e., equivalent to 3-1-2 kg N-P₂O₅-K₂O + 2 tons manure in 1000 m² of nursery area for one-hectare main field.

Main field preparation

For preparation of the main plot, the following points should be kept in mind

Transplanting

• Seedling age: 30-35-day old seedlings for long-duration, 25-30-day old seedlings for medium-duration, and 20-25-day old seedlings for short-duration varieties, are transplanted in a thoroughly prepared main field.
• Spacing: 20-25cm x 15cm (8-10 x 6 inches)
• Seedling density: 2-3 seedlings per hill.
• Depth of seedling: 4-5cm

Fertilizer

For transplanted rice, fertilizer recommendation per hectare is 60-20-40-5kg of N-P-K-Zn. The nitrogen dose is split into 3 applications - approximately 1/3rd as basal, 1/3rd at tillering, and 1/3rd at panicle initiation. Under submerged condition, additional 20kg N and 20kg K₂O is applied 5-7 days after recession of flood to facilitate regeneration, and boost recovery from flood-shock. The detailed schedule and method of applying all nutrients is given in the table below:

Weeding: Keep the field weed-free, especially during the early phase of crop growth. Weeds cause maximum damage in the early phase of the crop growth. But the later control is also important to prevent seed-setting by the weeds. Two weeding are done manually or mechanically (using paddy weeder or power weeder ); first at 3 weeks after, and second at 6 weeks after transplanting.

Herbicides: Herbicides should be selected based on presence of weed flora, and considering even previous weed pressure in the field.

Herbicide application

Herbicide safety:

Given below are some of the recommended herbicide-combinations. Depending on weed flora, follow the application timing and doses as per above table

Irrigation: In Sali season, in the absence of rain, application of 5 cm irrigation water 3 days after disappearance of ponding water is recommended in medium and heavy soils.

Plant protection measures: It is applied, if threshold levels of pests are present in the field. Follow plant protection measures as per state recommendations.

Harvest and post-harvest