【摘要】 从水稻土的抗切强度,压缩性,收缩性与水分含量的关系作了初步研究和讨论。水稻土的抗切强度随着湿度的降低而增高,塑性下限以下增加更为强烈,不存在一般所谓湿度稍低于塑性下限有一抗机械强度较小的酥软结持阶段。土壤(原状土)的压缩性以湿度大时为最高,随着湿度的降低而变小,接近塑性范围的中部,有一明显的转折点,在这转折点以下(或塑性范围的下部),土壤实际的压缩性是较小的。与旱地土壤的变化规律不一致。原因是水稻土垒结状况和粘结的条件不同。质地轻的土壤比粘重的土壤压缩性大,其压缩性降低至较小程度需要降低的土壤湿度比粘重的土壤为多,但其收缩变紧的程度不强烈,粘重水稻土在湿度降低时发生强烈收缩,使土壤变紧;当土壤湿度在塑性以下时,收缩引起土壤紧实的程度比一般人为的机械压力还更大,只有当湿度较大时,才有较高的总孔隙度。根据这些特性,提出水稻土秋耕适宜的土壤湿度是:以塑性下限为底限,以塑性中部为上限,对质地较轻的土壤,上下限宜酌量降低,但其上限不一定在塑性以下。适宜春耕的湿度比秋耕可大一些,因为晒垡和水中耕作,可再疏散土壤。更多还原

【Abstract】 Physical properties of three types of paddy soil collected from south Kiangsu province were studied.The shearing strength of paddy soils increases with the decrease ofmoisture content,especially below the lower plastic limit.Maximum compressibility ap-pears at the high moisture content and it falls sharply near the middle part of plasticityrange.As compared with the soils of heavy texture,the light paddy soils have a highercompressibility and lowering soil water content to a greater extent is necessary to reducetheir compression.The soil moisture causes shrinkage,especially for soils of heavy texture.Shrinkage makes the paddy soils more compact than mechanical pressure.It issuggested therefore that the optimum soil moisture for the fall cultivation ranges fromlower plastic limit to the medium plasticity and for the spring cultivation the optimummoisture content may be higher than in the fall.更多还原