新垦赤红壤结构特性的演化

CHANGES OF STRUCTURAL CHARACTERISTICS OF NEWLY CULTIVATED LATERITIC RED SOIL

本文探讨新垦赤红均结构特性的变化，定位试验结果表明：（１）在亚热带生物气候条件下垦殖赤红壤，由于耕作管理扰动土壤，将不可避免地产生土壤砂化或粉砂化现象。（２）新垦赤红壤在利用过程中，水稳性团聚体不断发生变化，较大粒径团聚体增多，较小粒径部分减少。（３）新垦赤红壤团聚体增加的原因，对豆科与非豆科作物轮作土壤来说，主要是土壤有机质含量有了提高；对多年生台湾草土壤来说，主要是植物根系的穿插作用。（４）作物轮作式土壤的容重、孔隙都有所改善，更有利于作物生长；多年生台湾草式的土壤孔隙度则有所减少。

This paper primarily discusses the changes of structural characteristics of newlycultivated lateritic red soil.Results are summarized as follows:(1) Under subtropical bioclimate condition,it was unavoidable for newly culti-vated lateritic red soil to be sandified due to disturbance by tillage and other mana-gemen practice. It was found that after cultivation,the contents of<0.001mm clayand<0.01mm physical clay in newly cultivated red soil reduced by 35-72%and10-20% respectively,0.05-0.01mm silt increased by 20-55%,while 3-0.05mmsand increased or decreased with the changes of silt content。(2)Waterstable aggregate composition of the lateritic red soil changed aftercultivation。>1mm aggregates increased more than one time over before cultivation,while<0.5mm aggregates decreased by 3-25%。 The increase of>1mm aggregatesin 0-20cm soil layer under different patterns of crop rotation was in the descend-ing sequence of perenial Taiwan grass>1: 1>1:2>2: 1￣* (3) Reasons for increase of larger aggregates were different for soils under dif-ferent use patterns. For soils with legume and non-legume crop rotation the incre-ase of larger aggregates might be attributed to the increase of organic matter,whilefor soil grown with perenial Taiwan grass it might be due to the grass root penera-tration and cutting,It was indicated that the more the soil organic matter,the morethe>1mm aggregates would be in the soil with legurne and non-legume crop rota-tion。(4)The bulk density and porosity in the soils with legume and non- legumecrop rotation gradually became more suitable for the growth of crops.Generally,the bulk density and capillary porosity rose in the 0-10cm soil layer but decreasedin the 10-20cm layer.But no increase in bulk density and porosity was found inthe soil grown with perenial Taiwan grass.