土壤磷扩散规律及其能量特征的研究──Ⅰ．水分、质地、温度及其相互作用对磷扩散的影响

DIFFUSION OF PHOSPHATE IN SOILS Ⅰ.THE INFLUENCE OF SOIL MOISTURE,TEXTURE AND TEMPERATURE AS WELL AS THEIR INTERACTIONS

用３２Ｐ示踪扩散池和扩散管法测定了４种不同质地土壤在不同含水量和温度下的磷自扩散系数。结果表明，非饱和土壤磷扩散系数（Ｄａ）随土壤水分含量（Ｗ）增加或土壤水吸力（Ｓ）减小而增大，符合幂函数Ｄａ＝ａＷｂ或Ｄａ＝ａＳ－ｂ关系；质地对磷扩散的影响与土壤水分条件密切相关，在同一含水量下，轻质土壤Ｄａ值大于粘质土，Ｄａ与粘粒含量呈显著负相关，而同吸力下与此恰好相反。饱和土壤磷扩散系数（Ｄｐ）比Ｄａ值通常大２—３个数量级，但不同土壤之间差异不大。５——４５℃范围内，每升温１０℃磷扩散系数增加量为１０％一５０％，平均为３０％左右。多元回归分析表明，水温相互作用对磷扩散有显著影响，其影响程度可用本文提出的磷扩散率水分系数和温度系数来表征。

Self-diffusion coefficients of phosphate in four soils of different texture at varying water content and temperature were measured by the methods of diffusion half-cells and diffusion tube using 32p-labelled KH2PO4 solution. The results showed that the apparent self-diffusion coefficient (Da)in the water unsaturated soils increased with increasing soil water content (W) or decreasing soil water suction (S). The relationship between Da and W or S could be described by the power equation of Da=aWb or Da=aS-b. The effect of soil texture on Da value was closely related with moisture condition. Under the same water content, the lighter the soil texture the higher the Da value, and a significant positive correlation of Da value with clay content was observed. On the contrary, at equal water suction, a negative correlation between Da value and clay content was found normally. The porous self-diffusion coefficient (Dp) in water saturated soil was higher 102-103 fold than the Da value of the soil, but there were no differences between the soils. The Da or Dp value increased with the temperature, and every increase of temperature 10℃ within 5℃ to 45℃ caused the Da or Dp value to increase by about 10-50%, with an average of 30% or so.Moreover, nonlinear multiple regression analyses were used to investigate the relation between the interaction of soil moisture with temperature and the self-diffusion coefficient of phosphate in soil. The analytical results indicated that the interaction influenced the diffusion of phosphate clearly,and the influencing extent could be defined by the concepts of "water coefficient"and "temperature coefficient "advanced in this paper.