Effect of Nitrate Levels on Nitrogen Accumulation, Seed Yield and Quality of Soybean Cultivars

Abstract

Soybeans (Glycine max [L.] Merr.) were grown in nutrient culture containing various concentrations of NO₃^- in the forms of KNO3 and Ca(NO₃)₂. The objective was to evaluate the seed yield and quality responses of soybean cultivars to NO₃^- solution. The experiment was conducted in a
hydroponic solution using a split plot in randomized complete blocks with three replications in the greenhouse at the Department of Agronomy, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand. Three levels of NO₃^- (5, 10, 15 mM) formed the main plots and three soybean cultivars (CKB1, SJ5, CM60) were the sub-plots. Nitrate application increased the yield of soybean cultivars and this increase was mainly associated with dry matter accumulation in leaves at R5. In comparison with the control (5 mM), the highest NO₃^- level (15 mM) resulted in higher leaf N accumulation at the R5 stage by an average of 82, 37 and 32% for SJ5, CKB1 and CM60, respectively. The maximum seed yield (41.43 g plant^-1) produced by the SJ5 cultivar under the highest NO₃^- level seemed to be supported by the significantly largest value of whole plant biomass and nitrogen content (%) in leaves at the R5 stage.