低丘红壤性水稻土土种及亚种的划分

划分水稻土土种,是以土体构型及诊断层的发育度为依据.为此,须首先确定水稻土的基本土层,规定层位段标准.因不同层位标准基本土层组成的土体构型,心土部位诊断层发育度相应有差异,以潴育型水稻土的渗育层为例,除形态特征不同外,中度发育的含结晶铁及晶胶率高,弱度发育的次之,强度发育的是无定形铁含量明显增高.耕作层肥力状况是划分亚种的主要依据,必须按理化性状及犁底层发育特征综合判断.

ON THE CLASSIFICATION OF SOIL SPECIES AND VARIETIES OF PADDY SOILS DERIVED FROM RED EARTH

The soil species of paddy soil are generally classified on the basis of the patterns of solum structure and the development degree of the diagnostic horizon.Therefore,the basic horizons of paddy soil should be established and the criteria for division of the horizons in soil solum should be defined in advance.Owing to the different patterns of solum structure,the developmant degree of the diagnostic horizon in subsoil is different.For example,in addition to the differences in morphological features,the periodically waterlogged paddy soil with moderately developed percogenic horizon is rich in crystalline iron and higher in ratio of crystalline iron to the amorphous iron in the horizon;and the soil with weakly developed percogenie horizon is commonly less in crystalline iron a.nd lower in the ratio of crystalline iron to amorphous iron in the horizon;while the soil with well developed percogenic horizon is rich in amorphous iron in the horizon.