Effect of differential soil moisture and nutrient regimes on postharvest attributes of onion (Allium cepa L.)

Studies were conducted to observe the effect of different soil moisture and nutrient regimes on postharvest attributes of onion irrigated with microsprinkler irrigation system under semi-arid climate for 3 consecutive years (2002–2004). Soil moisture regime consisted of four irrigation treatments based on pan evaporation replenishment (0.60, 0.80, 1.00 and 1.20 Ep). Similarly, three fertigation treatments were tried with nutrient application rates of 100 (50:25:25), 150 (75, 37.5, 37.5) and 200 (100:50:50) kg/ha of NPK. Irrigation and fertigation had marked effect on yield, postharvest attributes and storability of onion. Irrigation at 1.20 Ep and fertigation at 200 kg/ha produced higher bulb and dry matter yield, mean bulb size and weight, which decreased with the decrease in amount of irrigation and fertigation. The percentage of B-grade bulbs, which is considered commercially important, had been considerably higher at 1.20 Ep of irrigation and 200 kg/ha of fertigation. TSS increased up to 1.00 Ep and then declined slightly, whereas it varied with fertigation significantly. A decreasing trend for protein content was recorded with the increase in irrigation from 0.60 to 1.20 Ep, however, protein content increased with increase in fertigation. Irrigation at 0.80 Ep and fertigation @ 200 kg/ha resulted into minimum physiological loss in weight (%) for onion during 60 days of storage. But for extended storage period, increasing fertigation and decreasing irrigation had adverse effect on storability of bulbs. Theoretically, 416 mm irrigation water was found optimum for maximizing the dry matter yield of onion. Studies indicated that onion crop should be irrigated at 1.0 Ep under microsprinkler irrigation regime for better postharvest attributes. Similarly, fertigation @ 150 kg/ha is most desirable for micro sprinkler irrigated onion crop under semi-arid climate of India.