不同粒径沙土水分扩散率

Water diffusivity of sandy soils of different particle sizes

应用水平土柱入渗法测定了科尔沁沙地典型沙质农田不同粒径沙土的水分扩散率。结果表明：不同粒径沙土湿润锋迁移速率的大小依次是0．50—0．25mm、0．25—0．10mm、原状土、〈0．10mm的沙土；土壤粒径与入渗性能呈正比关系，即粒径大，则入渗快，反之则小；湿润锋迁移速率与入渗距离符合幂函数关系，相关分析结果均达到了极显著水平；粒径〈0．10mm的沙土，当土壤容积含水量〈0．415时，入值随含水量的增加而缓慢降低，而当含水量〉0．415时，入值则随含水量的增加而迅速降低；随着土壤粒径的减小，土壤水分扩散率逐渐降低，其大小依次是0．50—0．25mm、原状土、0．25—0．10mm、〈0．10mm的沙土；土壤容积含水率与土壤水扩散率符合经验公式并呈指数曲线变化，相关分析结果具有极显著的正相关关系。

Soil water movement parameters include its diffusivity, conductivity, and so on, which synthetically reflect the water retentively and movement capacity. It is absolutely necessary to research soil water movement regularity and to analyze soil water movement quantitatively with mathematical monitoring method. Unsaturated soil water diffusivity is an important hydraulic parameter for estimating irrigation quota, water infiltration and water loss. In this paper, water diffusivity of sandy soils of different particle sizes from typical sandy croplands are measured with the method of horizontal soil columns. The results show that the sequences of the wetting front advancement rates are 0.50 -0.25 mm, 0.25 -0.10 mm, undisturbed soil and sand soil of 〈0.10 mm. The infiltration capability is positively correlated to soil particle size, the relationship between infiltration distance and the rate of wetting front advancement is fitted as a power function. With the increase of soil water content, Boltzmann parameter decreases gradually, for the sandy soil of 〈0.10mm, when soil water content less than 0.415, the Boltzmann parameter decreases slowly with soil water content increasing, when soil water content is more than 0. 415, the Boltzmann parameter decreases rapidly. Water diffusivity decreases gradually with the decrease of soil particle size, the sequences of water diffusivity are 0.50 - 0.25 mm, undisturbed soil, 0.25 - 0. 10 mm and sand soil of 〈 0. 10mm. There is significant positive correlation between water diffusivity and soil water content, the relationship is consistent with a rule of exponential curve and conforms to the empirical equation.