Effects of physico-chemical properties of rhizosphere soils on uptakes of nutrients by rice.

点击翻译按钮获取中文摘要

Rhizobox was constructed in which soil solution samplers nad platinum electrodes were inserted in each compartment. Rice plants were grown in this rhizobox. Allophanic and smectitic soils were used for this experiment to investigate effects of physico-chemical change of rhizosphere soil by the observation of the differences between thses soils with distinct physicochemical properties. Soil solutions of different distances from rice root were collected every week. PH, NH4, Fe(ll), organic C, inorganic C concentration were measured for these solutions.The ways of NH4 uptake were different in allophanic and smectitic soils. In smectitic soil, in both phase I and phase II, uptake by mass flow was the major N uptake mechanism. This result was contradict with ordinary explanation by which NH4 uptake in phase II is explained by diffusive uptake. In phase II, the decrease in CEO by pH reduction enhanced NH4 mobility around rice root.In allophanic soil, in phase I, uptake by mass flow was the major N uptake mechanism, but in phase II uptake by diffusion was the major N uptake mechanism. Our results indicated that in phase I N accumulation into organic N proceeded and in phase It mineralization of the organic N enhanced NH4 uptake by rice root.Next, pecial rhizobox was constructed to take subsamples from rhizosphere during growth of rice plant. Organic N profiles in rhizosphere soils were distinct between allophanic and smectitic paddy soils. Buf by rapid decrease in hydro-conductivity of rhizobox did not allow to distinguish the detailed mechanism of N uptake in AIlophanic paddy soil.