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通过土壤水动力状态变化与土壤含水量和水势梯度之间关系试验研究,发现在降水或灌溉入渗过程中,土壤水系统将经历“吸水”(土壤含水量增大)、“过水”(含水量不变,且水通量不等于零)和“脱水”(含水量变小)过程,其总水势梯度大于、等于和小于1.0cmH2O/cm是重要标识特征。上述土壤水动力状态变化特征,在指导农田节水灌溉中具有独特作用。灌溉初期的水势梯度愈大,表明土壤水分亏缺愈严重,需要加大灌溉水量或延长灌溉时间;灌溉初期的水势梯度愈趋近1.0cmH2O/cm,表明土壤水亏缺愈少,应注意调控灌溉水量或限控灌溉时间,避免较多无效灌溉水量的发生。水势梯度等于1.0cmH2O/cm是降水或灌溉入渗过程中土壤含水量饱和的征兆,可作为灌溉节水调控的关键阈值,即当被监测土壤层的水势梯度趋近1.0cmH2O/cm时应结束该次灌溉。
Through the experimental study on the relationship between soil water dynamic state changes and soil water content and water potential gradient, it was found that the soil water system will experience “water absorption” (soil water content increase) during the process of precipitation or irrigation infiltration Water “(water content does not change, and the water flux is not equal to zero) and ” dehydration "(smaller water content), the total water potential gradient greater than, equal to and less than 1.0cmH2O / cm is an important identification features. The above characteristics of soil water dynamic state have a unique role in guiding water-saving irrigation in farmland. The greater the gradient of water potential in the initial period of irrigation, indicating that the more severe the soil water deficit, the need to increase the amount of irrigation water or prolong the irrigation time. The initial gradient of water potential approached 1.0cmH2O / cm, indicating that soil water deficit should be less and less Irrigation water or limited irrigation time to avoid more invalid irrigation water. The gradient of water potential equal to 1.0cmH2O / cm is a sign of saturation of soil moisture during precipitation or irrigation infiltration, which can be used as the key threshold for regulation of irrigation water saving. That is, when the water potential gradient of the monitored soil layer approaches 1.0cmH2O / cm The irrigation.