Soil, Climate and Crop Growth: Reading the Field Before You Sow
What this domain tests
This section checks whether you can connect soil properties and weather to crop choice, yield and season. Expect short-answer items on texture and structure, pH and liming, organic matter and cation exchange capacity (CEC), the agro-climatic zones of West Bengal, and the kharif–rabi–zaid calendar.
Soil properties you must be able to use
- Texture is the proportion of sand, silt and clay; structure is how those particles clump into aggregates. Loam is the best all-round texture.
- pH: the laterite red soils of Bankura, Purulia and Birbhum are strongly acidic (often pH 5.0–6.0) and need agricultural lime; Gangetic alluvial soils are near neutral; Sundarban coastal soils are saline-alkaline.
- Organic matter and humus raise water-holding capacity and CEC. Laterite soils are low in organic carbon, nitrogen and phosphorus.
- Depth, drainage and slope decide the crop: paddy tolerates poor drainage, most vegetables do not.
Climate and crop growth
Rainfall, temperature and photoperiod define three seasons: kharif (sown with the monsoon), rabi (sown October–November, ripening in cool dry weather) and zaid (a short summer crop). Growth runs through germination, vegetative, reproductive and maturity stages, each with a critical period - tillering and panicle initiation in rice, tuber initiation in potato.
Worked example
A field tests at pH 5.2 and needs 4 t/ha lime to reach pH 6.5, but the farmer can afford half. Reasoning: apply 2 t/ha, incorporate it 2–3 weeks before sowing, and re-test next season. Adding extra urea instead does not correct acidity, so the answer is not 'apply more nitrogen'.
Traps that cost marks
Confusing texture with structure; assuming alluvial soil is always fertile; forgetting that laterite is acidic; writing that sandy soil holds water well.