Soybean in Vidarbha: what to check, and when, from sowing to harvest

When should soybean be sown?

The ICAR soybean institute at Indore advises sowing only after 100 mm of rain, so that germination and growth last until the next spell of rain. Its 2026 advisory put the best window at the third week of June to the first week of July; that year the monsoon reached most soybean areas late. These advisories are written for central India; ask your KVK for your village.

Short and medium varieties mature in 90 to 100 days. Sowing time also changes the pests: a crop sown at the end of June escapes stem fly, while delayed sowing in July lowers girdle beetle (ICAR-IISR bulletin).

Dry spells and standing water

The seedling, flowering and pod-filling stages are the critical ones for moisture stress; stress then causes large yield losses (ICAR-IISR bulletin). The September 2026 advisory says a long dry spell hits hardest at pod filling. If a protective irrigation is possible, the bulletin says it should go on before cracks open in the soil.

In a dry spell, yellowing between the veins of the upper leaves can appear (July 2026 advisory). In continuous heavy rain, arrange drainage so that water does not stand (ICAR soybean institute).

Pests: when and what to look for

Girdle beetle: typically seen about 25 days after sowing; the female cuts girdles on the stem to lay eggs, and the part above droops and dries. Stem fly and whitefly come at the early stage, in July (ICAR soybean institute, 2026).

Tobacco caterpillar: young larvae feed together for 4 to 5 days on the green of the leaves, so infested plants are easy to spot. Green semilooper: small holes in leaves at first, then whole leaves eaten; worse with little rain, high temperature and high humidity. Pod borer: feeds on young pods first, then on the grains (ICAR-IISR bulletin).

Economic thresholds for monitoring, in larvae per metre of row: tobacco caterpillar 10 before flowering; semilooper 4 at flowering or 3 at podding; pod borer 10 at pod development (ICAR-IISR bulletin). Soybean can still yield normally with 20 to 25 per cent of its leaves lost. Check the crop regularly at 3 to 4 places in the field and note the caterpillars' stage. Ask your KVK before any spray.

Diseases that follow the weather

Yellow mosaic: small yellow patches or spots on young leaves at first; spread by whitefly. Mottled patterns and crinkling of the upper leaves are the signs (ICAR soybean institute).

Rust: mostly at flowering; the risk rises when leaves stay wet for 3 to 4 hours at 22 to 27 °C and 80 to 90 per cent humidity, and with night or morning fog. Sign: loose brown powder from burst pustules. Anthracnose: severe in long spells of drizzle with high humidity (ICAR-IISR bulletin).

Charcoal rot: shows when drought and 30 to 40 °C heat come between flowering and mature pods; split a plant and the taproot and lower stem show a light grey to silver colour (ICAR-IISR bulletin). Weed competition matters most 45 to 60 days after sowing.

When to harvest soybean

About 90 per cent of pods turning yellow is the right time to harvest (ICAR-IISR bulletin). Continuous rain at maturity can make seeds sprout in the pods and pods shatter, so the October 2026 advisory says to harvest soon after the crop matures.

What can the satellite tell you about soybean?

The satellite shows where and when greenness fell, for example a strip turning pale in a dry spell. It does not identify caterpillars, mosaic or rust; it points to the strip and you check it on the ground.

Kharif is the monsoon season, when cloud is a major problem for optical satellites (National Crop Forecast Centre, 2019): over one field near Katol, Sentinel-2 passed 23 times from July to September 2026 and saw the field clearly twice.