节水灌溉的土壤水分控制标准问题研究

A Study on the Soil Moisture Controlling Standard of Water saving Irrigation

农田土壤水分散失是在二个表面上进行的，一是土壤表面称之为蒸发，另外是作物表面称之为蒸腾。两者均与土壤水分呈线性相关，即随着土壤水分增大而增大。但土壤水分与光合速率关系研究表明，当土壤水分低于６５～６９％田持时，随着土壤水分增大光合速率增大，若土壤水分高于６５～６９％田持时，随着土壤水分增大光合速率降低。光合作用对土壤水分有一阈值反应。

The vaporization loss of soil moisture in farmland happens on two surfaces:one on the soil surface,being called as evaporation;another on the crop surface,being refered to as transpiration.They are both linearly related to soil moisture.Namely,they increase with the increase in soil moisture. Studies of the relationship between soil water and photosynthetic rate have shown that the photosynthetic rate increased with the increase in soil water when soil water is less than 65～69% of field capacity.While soil water is higher than 65～69% of field capacity,the photosynthetic rate decreases as soil moisture increases.Therefore,photosynthesis makes a threshold response to soil moisture.The threshold can be taken as the soil moisture controlling standard of water saving irrigation in the fields.