Agronomy and Crop Production: Seasons, Seed Rate and Crop Sequences
The crop year in Assam
Cropping in Assam is organised around three rice ecologies. Ahu (autumn) rice is broadcast or transplanted in March–April and harvested June–July. Sali (winter) rice is the principal crop: nursery in May–June, transplanting June–July, harvest November–December. Boro rice is transplanted in November–December on low-lying irrigated land and harvested April–May. Rabi crops - mustard, lentil, pea, potato, wheat and vegetables - follow Sali rice where residual moisture allows, and this sequence drives the state's cropping intensity.
Core agronomic rules
- Land preparation: two to three ploughings plus puddling for transplanted rice; fine, firm tilth for small-seeded rabi crops.
- Seed rate is a calculated value, corrected for germination and purity - never quoted in isolation.
- Spacing fixes plant population, tillering, light interception and ultimately yield.
- Rotate cereals with legumes to break pest cycles and add nitrogen.
- Sowing date is a yield input: late Sali transplanting pushes flowering into low-temperature stress.
Worked example
Target population 100 plants/m²; 1,000-grain weight 20 g; laboratory germination 80 per cent. Plants/ha = 100 × 10,000 = 10,00,000. Viable seeds needed = 10,00,000 ÷ 0.80 = 12,50,000 seeds/ha. Seed rate = (12,50,000 × 20 g) ÷ 1000 = 25,000 g = 25 kg/ha. For 0.4 ha the requirement is 10 kg. Ignoring germination would have given 20 kg/ha and a thin stand.
Traps that cost marks
- Swapping Boro and Ahu seasons.
- Entering test weight in milligrams, which shifts the answer by a factor of 1000.
- Giving a seed rate without stating spacing and germination basis.
- Treating cropping intensity and crop rotation as the same concept.