Abstract
In a field study during Rabi 2000-2001 and 2001-2002, nutrient (N, P, and S) contents and their ratios (N:S, N:P, and S:P) in onion leaves at 9, 12, and 15 weeks after transplanting (WAT) were correlated with bulb yield and allied parameters. By and large, N, P, and S contents (%), and S:P ratio in onion leaves at 9 WAT were found positively, and N:S and N:P ratios negatively related to bulb yield, plant height, number of leaves per plant, and weight of 10 bulbs to a significant extent during both years of study. Similar relationships of N and S contents and N:S ratios in onion leaves at 12 and 15 WAT continued to exist with these parameters. However, at the nine weeks stage, per cent dry weight was found to be negatively related with P and S contents and positively with N:S, N:P, and S:P ratios to a significant extent. Correlations, as indicated by correlation coefficients (r values), were more pronounced during the second year compared to first due to warmer weather. Sulphur among nutrients and N:S ratio among three ratios were found to be good determinants of the performance of the onion crop. Nitrogen and S contents and N:P ratios ranging from 2.03 to 2.55%, 0.27 to 0.34%, and 8.8 to 9.4, respectively, were found to be critical for onion yield at 9 WAT. Similarly, P content and N:S and S:P ratios critical for yield, were 0.23% and 7.5 and 1.24, respectively. At 12 weeks of age, critical N and S contents and N:S ratio increased to 4.1 and 0.39%, and 10, respectively. Sulphur content critical for onion yield decreased to 0.35% at 15 WAT.
