Effects of Genotype and Nitrogen Fertilizer on Growth and Yield of Soybean when Planted under Saturated Soil Culture

Abstract

Two experiment were conducted in the early rainy seasons in order to study the effects of genotypes and rates of nitrogen fertilizer on growth and yield of soybean grown under saturated soil culture (SSC). A split-split plot design with three replications was used for each experiment. Main plots composed of growing soybeans alone on beds and growing soybeans on beds and transplanted rice in the furrows. Both treatments were kept under saturated soil culture condition. Sub-plots composed of two soybean cultivars, Chiang Mai 60 and Leichhardt while sub-sub-plots consisted of four rates of nitrogen fertilizer, 0, 31.2, 62.5 and 125.0 kg N/ha applied on beds. Results of the experiments revealed that yield of soybeans planted as monoculture under SSC was significantly higher than those intercropped with rice in both of the early rainy and dry seasons . In the early rainy season, cultivar Leichhardt out yielded cultivar Chaing Mai 60 while there were no significant differences in yield between two cultivars in the dry season. The difference in yield of soybeans as affected by nitrogen fertilizer was not detected in both experiments. The number of pods per plant and total dry matter per unit area of soybean responsed to the treatments given in the same manners as the yield of soybean. In this study, it has been found that soybean planted under saturated soil culture demonstrated high rate of nitrogen fixation both in the rainy and dry season. This might be the reason to explain why the response to nitrogen fertilizer were not detected in this study