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

构建根箱，在每个隔间内插入土壤溶液取样器和铂电极。水稻种植在这个根箱里。本试验以异生型和密生型土壤为研究对象，通过观察不同理化性质土壤间的差异，探讨根际土壤理化变化的影响。每周收集离水稻根系不同距离的土壤溶液。测定了这些溶液的PH、NH4、Fe（ll）、有机C、无机C浓度。同种异质土和同种异质土对NH4的吸收方式不同。在ⅰ期和ⅱ期均以质量流吸收为主要的氮素吸收机制。这一结果与一般解释相NH4的吸收是由扩散吸收来解释的解释相矛盾。在第二阶段，pH降低导致的CEO降低增强了水稻根系周围NH4的流动性。在异形土中，第一阶段以质量流吸收为主，第二阶段以扩散吸收为主。结果表明，ⅰ期氮素向有机氮积累，ⅰ期有机氮矿化促进了水稻根系对NH4的吸收。其次，构建了专门的根箱，在水稻生长过程中采集根际亚样。异晶型和密晶型水稻土根际土壤有机氮分布明显不同。但通过根际导水率的快速下降，还不能区分嗜磷水稻土氮吸收的详细机制。

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.