OPTIMUM LEAF LEVELS OF NITROGEN, PHOSPHORUS AND POTASSIUM IN SWEET CORN AND SNAP BEANS

Publisher Website
Google Scholar
Abstract
Optimum nutrient levels were derived by comparing the polynomial regression curves relating leaf analyses and crop yields with rates of applied nitrogen, phosphorus and potassium. Uppermost mature leaves were used for analysis, and samples were collected at specific physiological stages of development.In two seasons the optimum levels in sweet corn differed by 7, 25 and 9 per cent, and in snap beans by 12, 29 and 11 per cent for nitrogen, phosphorus and potassium respectively. A low moisture supply was generally associated with lower optimum levels for all three nutrients, but "excess" moisture had only slight effects on these levels for any nutrient.Optimum nutrient levels which were calculated from ample moisture conditions were, for the tassel-emerging stage of sweet corn, 3.5, 0.38 and 2.5 per cent, and at the early flower stage of snap beans 5.1, 0.40 and 2.0 per cent for nitrogen, phosphorus and potassium, respectively. At the sixth to seventh leaf stage of sweet corn optimum levels were higher for nitrogen and potassium but lower for phosphorus (3.8, 3.1 and 0.34 per cent respectively), and at the pollen-shedding stage the levels were only slightly different than at tassel-emergence.