Nitrogen and potassium levels on the onion yield and storage with different planting times

The objective of this work was to evaluate the effect of different planting times and nitrogen and potassium levels on onion yield and postharvest storage, cultivar Texas Grano 502 PRR. Two trials were carried out from March to November 2001 and from August 2001 to March 2002, in Brazilian Northeast. A randomized complete block design with split-plot in a 4x3 factorial scheme was used. The plots consisted of planting dates ( March and August) and the subplots of the factorial involving four levels of nitrogen ( 0, 60, 120 and 180 kg ha(-1)) and three levels of potassium (0, 90 and 180 kg ha(-1) K2O) with three replications. The March planting showed higher commercial yield ( 66.5 Mg ha(-1)) than August plating ( 41.4 Mg ha(-1)). In the absence of the potassium fertilization and at the level of 90 kg ha(-1) of K2O, linear increments were observed in the commercial yield according to nitrogen fertilization, while at 180 kg ha(-1) of K2O, the nitrogen fertilization showed quadratic behavior, with point of minimum yield at 23.5 kg ha(-1). Regarding non-commercial yield ( culls), the March planting obtained 6.0 Mg ha(-1) and August 5.4 Mg ha(-1). Significant effects of N, K and of the interaction were observed for bulb mass loss at 40 and 80 days after cure.