Nutritional Quality of Vegetable Crops as Affected by Phosphorus and Zinc Fertilizers1

Abstract

AbstractThe nutritional quality as well as the yield of the portions of vegetable plants used for human consumption should be considered in fertilization programs.The purpose of this study was to Determine the effects of rates of concentrated superphosphate and zinc sources on some nutritionally important factors including the concentration of P, Zn, phytic acid (myoinositol hexaphosphoric acid), and oxalic acid in the edible portions of four vegetables. The plants, pea (Pisum sativum L.), snap bean [Phaseolus vulgaris (L.) var. humilis], cabbage (Brassica oleracea var. capitata), and table beet (Beta vulgaris L.) were grown on a Honeoye fine sandy loam (Glossoboric Rapludalf, fine loamy, mixed mesic) derived from calcareous glacial till. These crops were fertilized with concentrated superphosphate (CSP) at rates of 0, 30, 60, and 120 kg P/ha, and ZnSO4 or ZnCl2 at rates of 0, 5, 20, and 80 kg Zn/ha applied in a band at planting time in a factorially designed experiment. The plants were sampled at processing stage except that pea and snap bean seeds were also sampled at full maturity. Increasing fertilizer CSP rates increased yields and P concentrations in all crops. Fertilizer CSP increased phytic acid concentrations in immature and mature pea seeds and in mature snap bean seeds. Oxalic acid concentrations in table beet plants decreased with increasing rates of CSP fertilizer. Fertilizer CSP without Zn fertilizer decreased Zn concentrations in the plants, but CSP with Zn fertilizer generally increased Zn concentrations. Fertilizer Zn did not affect yields nor cause visible plant toxicities. However, Zn fertilizer increased Zn concentrations in the plants, especially when applied with high rates of CSP fertilizer. Thus, CSP fertilization without Zn fertilization of vegetable crops can reduce their nutritional quality by lowering their Zn concentrations. However, the concomitant use of Zn fertilizer, with high rates of CSP fertilization, can improve the nutritional quality of vegetable crops with respect to Zn.