Liming and Water Limits on a Bankura Laterite Holding
Sabita Mondal cultivates 0.60 ha of red laterite land near Khatra in Bankura. A soil test this March reports pH 5.2, organic carbon 0.38%, available nitrogen low, available phosphorus 22 kg/ha and available potassium 115 kg/ha; the block office notes high exchangeable acidity. Rainfall is about 1,150 mm, almost all of it between June and September. Her only irrigation is a dug well that usually holds water until early January. For years she has taken one rainfed transplanted aman rice crop (about 2.8 t/ha) and left the land fallow afterwards. This year she has saved ₹18,000 and wants to grow tomato and cauliflower on the whole 0.60 ha for the local haat, using the well. Last season the seedlings in her raised nursery bed collapsed in small patches, with a water-soaked rot at the collar; she blamed the seed trader and bought fresh seed from another shop.
1. Identify the two soil-related constraints that most limit her winter vegetables, and state what she should apply, in what quantity for 0.60 ha, and when.
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Two constraints stand out from the report and from the soil type:
- Acidity (pH 5.2 with high exchangeable acidity). Below pH 5.5, aluminium and iron in laterite soil fix phosphate, molybdenum becomes unavailable and root tips are damaged, so fertilizer alone gives a poor response. She should apply agricultural lime at about 2 t/ha - roughly 1.2 t for 0.60 ha - broadcast and mixed into the top 10–15 cm at least 2–3 weeks before planting. Lime must not be mixed with urea, DAP or ammonium sulphate at the same time, because ammonium nitrogen is lost as ammonia gas; keep them a fortnight apart.
- Very low organic carbon (0.38%). Apply 8–10 t/ha of well-rotted FYM or compost, i.e. 5–6 t for her area, and add glyricidia loppings or a green-manure crop. Organic matter holds moisture in a shallow laterite profile, feeds the microbes that release locked phosphorus, and improves the physical condition of the bed.
Nitrogen is low and P and K only medium, so a soil-test-based NPK dose is still needed - but lime and organic matter are what allow that fertilizer to work.
2. She plans to irrigate the whole 0.60 ha of tomato and cauliflower from the dug well until harvest. Is that realistic? What would you advise?
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It is not realistic. A tomato crop needs roughly 5–7 irrigations of 5 cm each; on 0.60 ha one 5 cm irrigation is 0.60 × 10,000 m² × 0.05 m = 300 m³, about 3 lakh litres, and a dug well of that command rarely delivers it, especially one that dries by early January. Cauliflower needs steady moisture from curd formation onwards; stress gives small, ricey curds, while tomato shows blossom-end rot and fruit cracking when moisture swings.
A workable plan is to put vegetables on only 0.15–0.20 ha around the well, mulch with straw to cut evaporation, irrigate in furrows rather than by flooding, and use the remaining 0.40 ha for a low-water rabi crop such as lentil, mustard, chickpea or linseed that can finish on residual moisture. She should also deepen or line the well and store rainwater. The area sown should follow the water available, not the other way round.
3. Was the seed the cause of the nursery collapse? What should she do differently next season?
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The pattern suggests the seed was not the main cause. Patchy collapse with a water-soaked rot at the collar, spreading from the wettest spots, is damping-off (Pythium/Rhizoctonia), a soil- and water-borne problem. It is favoured by unsterilised nursery soil, dense sowing, shade, poor drainage and evening overhead watering; fresh seed from a new shop will fail in the same way if the bed is unchanged.
What she should do:
- raise beds about 15 cm high with a friable mix of soil, sand and well-decomposed FYM;
- solarise the bed under clear polythene for 2–3 weeks, or drench with Trichoderma viride at about 5 g/kg of nursery soil;
- sow thinly in lines and water in the morning, not in the evening;
- never use fresh manure on the nursery bed;
- treat seed with Trichoderma or thiram, and shift the nursery site each year.
If patches appear, remove affected seedlings and drench the bed with a copper-based or metalaxyl-type fungicide before watering. Liming the main field also reduces the problem later.