Transformations of fertilizer nitrogen in soil-plant system with special reference to comparison between submerged conditions and upland field conditions

Abstract

Abstract We investigated quantitatively the difference in N transformations in soil between submerged conditions and upland field conditions by using 15N-a mmonium. We also investigated the effect of the water conditions on the distribution of 15N fertilizer in rice plant and soil organic matter in greenhouse experiments. In the soil incubation experiment without plants, the amount of immobilized 15N in soil organic matter under upland field conditions increased rapidly during the initial period, but gradually decreased during the later period . The amount of immobilized 15N under submerged conditions continued to increase until the later period . In the pot experiment where plants were present, the amount of immobilized 15N in soil organic matter under submerged conditions was larger than that under upland field conditions, and the availability of the applied 15N to plants was larger under upland field conditions. Under upland field conditions, the 15N-ammonium immobilized by soil microorganisms was pres...