Onion tip burn: Significance, and response to amount and form of nitrogen

•Leaf tip burning in onion transplants proceeds after transplanting to reduce bulb yield.•A nitrogen induced boost to vegetative growth can recover plants from leaf tip burning by 42%.•Nitrate-N decreases whereas ammonium-N increases leaf tip burning of onion. Leaf tip burn in onion is a symptom of a number of biotic and abiotic stresses. It may appear in densely cultivated nursery transplants owing to one or the other simple or complex reasons. The present research work was planned to know the impact of rate and form of nitrogen (N) on post-transplantation recovery of tip burnt transplants, and significance of the disorder. Tip burn transplants were cultivated on sand culture hydroponic system at 0, 4, 6 and 8 mM N. In second trial 4 mM N was maintained in nutrient solution as 4:0, 3:1, 2:2 and 0:4 mM NO3-N: NH4-N ratios. N supply linearly increased total leaf length (TLL). Both high and low N levels and replacement of NO3-N with NH4-N in solution significantly increased burnt leaf length (BTL). Lowest BTL and highest bulb yield was noted at 4 mM N and at 4:0 mM NO3-N : NH4-N ratio. N induced increase in TLL significantly reduced BTL by 42% at 60 and 75 days after transplanting (DAT). In both the trials BTL, particularly at early growth stages, was linearly and negatively linked to bulb yield of onion. Depending upon the DAT, the suggested linear regression models described about 50% variation in bulb yield counted for BTL. It is concluded from the results that leaf tip burning in onion is of great importance regarding bulb yield and a reasonable recovery is possible through appropriate dose of nitrate nitrogen.