Blossom-End Rot in Drip-Irrigated Tomato on Calcareous Soil
Ramesh Patil grows 0.4 ha of tomato (cv. Abhinav) on raised beds with drip in Jalgaon. Soil test: pH 8.2, free lime 9%, EC 0.38 dS/m, organic carbon 0.42%. At planting he incorporated 10 t FYM/ha, 150 kg DAP/ha and 50 kg MOP/ha; top-dressing was 100 kg urea/ha in three splits through drip. At 45 days after transplanting, 15–20% of fruits on the first three trusses show a dark brown, leathery, sunken patch at the blossom end. Foliage looks normal and there is no wilting. Irrigation is given every third day for 45 minutes; the field was dry for four days during a pump repair. Night temperature has been 24–26°C and day 33–35°C. The farmer suspects a fungal disease and wants to spray carbendazim plus a calcium foliar spray.
1. Diagnose the disorder and explain why it appeared although the soil is calcareous.
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Diagnosis: blossom-end rot (BER), a calcium-related physiological disorder - not a fungal disease. The soil is calcareous (pH 8.2, 9% free lime), so total calcium is high but soluble Ca²⁺ is low. DAP and urea supply ammonium, which competes with Ca²⁺ uptake, and MOP adds K, another antagonist. Calcium moves in the xylem with transpiration and is immobile in the phloem; leaves transpire strongly and look normal while the fruit tip - a low-transpiration organ - is starved. The four-day dry spell followed by heavy irrigation caused a growth flush and disrupted Ca supply to expanding fruit. Carbendazim will do nothing. Split fruit and secondary rots may follow, but the primary cause is nutritional and moisture-related.
2. Give a two-week corrective plan for the standing crop, including irrigation, fertigation and foliar measures, and state what not to do.
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Immediate actions: remove and destroy affected fruits so they do not become rot sources; do not apply more urea. Irrigate lightly and frequently - for example 20–25 minutes daily instead of 45 minutes every third day - to keep moisture uniform, and mulch the beds. Foliar Ca: calcium chloride 0.5% or calcium nitrate 0.5% with a spreader, two or three sprays at 7–10-day intervals directed at new trusses; this is preventive for new fruit, not curative for already affected fruit. Fertigation: replace part of the urea with calcium nitrate, about 10 kg per 0.4 ha per week split through drip, and avoid tank-mixing calcium with phosphate or sulphate fertilizers. Reduce K until soil test supports more. Do not over-irrigate to “flush” salts; that worsens moisture fluctuation. Record EC and pH of the drip solution.
3. What pre-plant soil and nutrition changes would you make for the next season?
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Test again and address the calcareous, high-pH soil before planting. Add 15–20 t/ha well-decomposed FYM or compost and a green manure crop to improve structure and rooting. Use gypsum where soil-test Ca and sodium status justify it, and consider elemental sulphur only if pH reduction is the goal; both need soil-test-based doses. Band phosphorus near the root zone rather than broadcasting, and avoid heavy ammonium or potassium applications during fruiting. Prefer calcium ammonium nitrate or calcium nitrate for part of the N. Mulch and schedule drip by tensiometer or pan evaporation so the root zone never dries sharply. Monitor petiole/leaf Ca at flowering and keep a record of fruit quality. Variety choice and uniform moisture matter as much as the fertilizer bag.