Effect of Directly-Applied and Residual Boron on Nutrition in French Bean-Cabbage Cropping Sequence under Alfisol

Effects of directly-applied-to-the-soil and residual boron (B) in soil were assessed in French bean (Phaseolus vulgaris L.) - cabbage (Brassica oleracea var. capitata L.) cropping sequence and cycle under Alfisol, with either low or adequate hot-water-soluble boron (HWS-B) content. The experiments focussed on effects of various levels of applied B on leaf tissue B and crop yield, HWS-B content in the year of B application, and in subsequent years. Response of the crops to applied B reflected initial soil B levels. Application of the highest level of B (8kg ha^-1) reduced crop yield at Site-I throughout the four years of experimentation. Applied B up to 2kg ha^-1 enhanced French bean yields at Site I, while at Site II, at all the levels of applied B, yields were reduced in the first two crops; during the third and fourth crop, yields in plots receiving 1kg B ha^-1 were higher than those in plots that did not receive supplemental B. In both French bean and cabbage, high B concentrations caused toxicity symptoms manifested as browning of leaf margin. These symptoms appeared in both French bean and cabbage under all the plots receiving B e" 4kg ha^-1. Monitoring HWS-B content at harvest in each crop during the experiment indicated that applied B diminished rapidly in these soils. However, at Site II, residual HWS-B was above the critical level throughout the period of experimentation. A single application of higher amounts of B fertilizer led to B toxicity and caused yield suppression in these vegetables. French bean, being a sensitive crop, should be grown preferably on residual B rather than subjecting it to direct application of B in any vegetable cropping system under red soils.