玉米灌溉田土壤水分变化及其耗水规律研究

以辽宁省主要旱地作物玉米为研究对象，研究了其灌溉田土壤水分变化及其耗水规律。在试验条件下，0～20 cm土层水分含量最低，整个玉米生育期内水分变化幅度最大；30～50 cm土层由于受长期耕作习惯等因素的影响土壤的黏滞度较高，保持较明显的水分梯度，并使50～90 cm土层水分变化与0～20 cm土层相比滞后1～3 d；90～120 cm土层土壤水分受根系影响较小，变化不大。玉米生育前期农田实际蒸散量和参考蒸散量均趋于不断增大，生育中期个别时段内由于受阴雨气候影响蒸散量有所减弱；参考蒸散量最大值出现在玉米播种后第46天左右，农田实际蒸散量最大值出现在玉米出苗后第96天左右，玉米生育后期两者逐渐减弱。玉米生育前期表层土壤棵间蒸发量占实际蒸散量的比重较大，生育中期棵间蒸发量受降雨和灌溉等因素影响，变化幅度较大，生育后期相对较小。随着玉米叶面积增加，作物系数不断增加，在播种后第81天左右作物系数达最大值，之后作物系数逐渐下降。

Study on the Law of Soil Moisture and Evapo-transpiration Changes in the Irrigated Corn Farmland

We had studied law changes of soil moisture and evapo-transpiration in irrigated farmland of corn which was the principal crop of dry farmland in Liaoning province. The results indicated that the minimum moisture content of soil was in the soil layer 0 - 20 cm where moisture fluctuation ranged the most widely in the whole crop growth and development period. In contrast, the change of moisture was modest in the soil layer 30 - 50 cm where the water content of the soil keeped a gradient clearly. The change of the moisture in the soil layer 50 - 90 cm lagged the layer 0 - 20 cm, though the change in the two soil layers were parallel. The actual measured evaporation and the reference evapotranspiration increased greatly in the earlier stage of crop growth and development period. The evaporation was weak sometimes in the intermediate stage of crop growth and development period for various reasons, especially for the overcast sky. The maximum of reference evapotranspiration at the 46th day after sowing and the maximum of actual measured evaporation at the 96th day after sowing. Both decreased gradually in the later stage of crop growth and development period. The proportion of plant interspace evaporation to actual measurement evaporation was higher in the earlier stage of crop growth and development period. The proportion was changed in evidence in the intermediate stage, because of the rainfall and irrigation. And the proportion was smaller in the later stage. The crop coefficient increase with leaves area. The maximum crop coefficient at the 81st day after sowing, and then it became weak gradually.