Effects of nitrogen fertilization on stored cabbage.

Abstract

The development of three physiological disorders of stored cabbage was studied in 1984-85 and 1985-86 on the tolerant cv. Hidena and susceptible cv. Safekeeper, after 126, 180 or 310 days of storage at 1°C and 95 % r. h. Cabbages were from field plots where treatments of 0, 90,180 or 270 kg N ha-1 of calcium nitrate, ammonium nitrate or ammonium sulphate were applied before transplanting. Yield, head weight and head density were measured at harvest and weight losses at storage removal. The severity of black midrib increased linearly with N rates, in 1984—85 the disorder occurred in storage. On the susceptible cv. Safekeeper, grey speck disease and vein streaking were generally severe even at low N rates; these two disorders also developed less rapidly than black midrib up to the maximal severity in storage on heads treated with high N. High N in general, and calcium nitrate more particularly, reduced maturity at harvest and promoted the development of grey speck disease, rooting and the break of dormancy after 310 days of storage. Fertilization with nitrates compared with ammoniuim sulphate occasionally increased vein streaking. Application of N fertilizers in excess of 180 kg N ha'1 must be avoided, nitrates should be used carefully, and a tolerant cultivar planted, to ensure high quality cabbage for long-term storage.