The role of subsoil on the crop production-subsoil edaphology.

底土和表层土壤一样，在为作物提供水分和养分方面起着重要作用。在日本等潮湿地区，肥沃的养分很容易通过降雨从表层迁移到底土。摘要本研究旨在研究不同黏土矿物条件下具有代表性的日本安土对作物生长和氮素吸收的影响，以及氮素控制效价肥（CAF）抑制根系向地下发育对土壤中作物生长的影响。本研究采用弱酸性的异硫磷和强酸性的非异硫磷与2:1矿物。试验处理为根系伸长限于表层（15 cm深）的表层土壤处理和根系可发育至45 cm厚的深层土壤处理。两种土壤地下样地燕麦和大麦的总干物质和产量均大于表层样地。地下样地氮素吸收量是表层样地的1.7 ~ 3.3倍。燕麦分别从allophanic和nonallophanic底土中吸收了约70%和50%的总氮。在对铝毒性敏感的大麦中，非异源土对底土氮吸收占总吸收量的比例（42%）低于异源土（65%）。在高毒铝含量的非allophanic土中，由于存在2:1的矿物质和较低的ph，大麦根系不能延伸到更深的底土中。结果表明，在日本湿润气候条件下，地下土壤在为作物提供肥料和土壤矿化氮，促进作物生长和粮食产量方面发挥着重要作用。底土对作物生长的贡献受与土壤酸度有关的土壤粘土矿物的影响。在土壤中施用cafn能有效地促进作物生长和粮食产量，抑制根系向底土伸长。砂质水稻土的铵离子持持能力低于粘土土。砂质土壤水稻产量和氮肥利用效率低于粘土土壤。砂质水稻土的生产力对底土供氮能力的依赖性较强。少

Subsoil, as well as surface soil, has an important role in supplying water and nutrients to crops. Fertilized nutrients easily migrate from surface layr to subsoil by rainfall in the humid regions such as Japan. The objectives of this study are to determine the effects of subsoil on the growth and nitrogen (N) uptake of crops in representative Japanese Andisols with different clay mineralogy, and the effect of controlled availability fertilizer (CAF) of N on the crop growth in soils inhibiting root development to subsoil. Weakly acidic allophanic Andisol and strongly acidic nonallophanic Andisol with 2 : 1 minerals were used in this study. Experimental treatments were surface soil plot where root elongation was limited to surface layr (15 cm depth) and subsoil plot where crop root can develop into subsoil (45 cm thickness). Total dry matter and grain yield of oats and barley in the subsoil plots were greater than those in the surface soil plots in both soils. Nitrogen uptake of both cr … More ops in subsoil plots were 1.7 to 3.3 times as much as in the surface soil plots. Oats absorbed about 70 % and 50 % of total uptake N from allophanic and nonallophanic subsoil, respectively. In the case of barley with sensitivity to Al toxicity, the ratios of N absorbed from subsoil to total uptake in nonallophanic soil (42%) were lower than those in allophanic soil (65%). Barley roots could not extend to deeper subsoil in nonallophanic soil with high toxic Al level due to presence of 2 : 1 minerals and low pH.Application of CAF-N increased growth and N uptake of crops in each surface soil plots.It was concluded that subsoil playd a signiflcant role in supplying fertilizer and soil-mineralized N to crops and in increasing the crop growth and the grain yield under humid climate of Japan. The contribution of subsoil to the crop growth was affected by soil clay mineralogy relating soil acidity. Application of CAF-N was effective for improving the crop growth and the grain yield in soils inhibiting root elongation into subsoil.Sandy paddy soil showed lower holding capacity of ammonium ion compared to clayy soil. Rice yield and utilization efficiency of fertilizer nitrogen was lower in sandy soil than clayy soil. Productivity of sandy paddy soil depended more strongly on nitrogen supplying ability of subsoil than clayy paddy soil. Less