Effects of Nitrogen Forms and Ratios on the Contents of Mineral Nutrients in Vegetable Soybean Seeds

Using vermiculite culture,the effects of NO3——N∶NH+4-N ratios on the contents of mineral nutrients in developing seeds of vegetable soybean [Glycine max(L.) Merr.cv.Li-xiang 95-1] were studied.The results showed that the appropriate NH+4-N ratio between 25% and 50% in nutrient solutions was beneficial to the growth and development of vegetable soybean,also the fresh and dry weight of biomass(including stem,leaf,root and pod) increased significantly.Under the treatment of excessive NO3-(100%) or NH4+(75%),both biomass production decreased obviously,especially in NH4+(75%).The contents of total N and P increased obviously under the NO3-∶NH4+ treatment of 25∶75,but the contents of K,Ca and Mg decreased obviously.However,the changes of mineral nutrient contents were just the opposite in the NO3-∶NH4+ treatments of 75∶25 and 50∶50,in which the contents of K,Ca and Mg maintained at high levels.Therefore,the high contents of mineral nutrients under the appropriate ratios of nitrogen forms were beneficial to the development of vegetable soybean seeds,but the excessive NH4+ was harmful to the uptake of mineral nutrients.