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在实验室条件下,模拟稻茬和麦茬两种土壤状况,研究了抗机械强度、变形性质和内压力三者与土壤含水量的关系。稻茬田土壤抗机械强度随含水量变化的曲线的坡度很大,麦茬田则较小。前者因强烈收缩使分子引力很快发展之故。粘质土壤的内摩擦力,在含水量大时接近于零,抗剪强度只决定于内聚力,质地变轻内摩擦力微有呈现。含水量降低各种土壤内摩擦力增加快,并受土壤剪断面的粗糙度和团聚体强度所影响。土壤含水量降低到塑性下部,土壤脆性开始形成,但仍有一定的塑性和粘滞性,土壤质地变轻及垒结疏松时,土壤的脆性能够在更高的含水量范围内产生。土壤塑性体与固体的转变是渐次过渡的,所以二者的分界应是一个较大的湿度范围。稻茬田土壤含水量降低内压力增加很快,特别是粘质水稻土。所以我们认为水稻土耕作时湿度不宜过低,克服水稻土的塑性和粘滞性是耕作上的首要任务。为此,犁要能使土壤形成较小的初剪面土块,耕速要大,在播种期前先耕翻,并于播种时复耕。同时为发挥机具的曳引力,其行走部分与土壤的接触面积宜大。
Under laboratory conditions, two soil conditions, rice stubble and wheat stubble, were simulated. The relationship between mechanical strength, deformability and internal pressure and soil water content was studied. The slope of soil resistance to mechanical stress in rice stubble field varies greatly with the change of water content, while wheat stubble field is smaller. The former due to strong contraction of molecular gravitational rapid development. The internal friction of clayey soil is close to zero when the water content is large, the shear strength is only determined by the cohesion, and the texture becomes lighter with the slight internal friction. Decrease in water content Friction in various soils increases rapidly and is affected by the roughness of the sheared soil surface and aggregate strength. The soil water content decreased to the lower part of plasticity, soil brittleness began to form, but there was still some plasticity and viscosity. Soil brittleness could be produced in a higher water content when the soil texture became lighter and the bulge became stronger. The transformation of soil plasticity and solid is a gradual transition, so the boundary between the two should be a larger humidity range. Decreasing soil water content in rice stubble field increases rapidly, especially viscous paddy soil. Therefore, we think that the soil moisture should not be too low when it is cultivated. Overcoming the plasticity and viscosity of paddy soil is the primary task of farming. For this reason, the plow should be able to make the soil form a smaller primary cut clods, the tillage speed should be larger, the tillage should be done before sowing, and the tillage should be re-cultivated. At the same time to play the traction of the machine, the contact area of the walking part of the soil should be large.