陇中黄土高原不同种植年限苜蓿草地土壤水分及产量响应

Soil moisture and alfalfa productivity response from different years of growth on the Loess Plateau of central Gansu

本研究利用黄土高原西部典型半干旱雨养农业区不同种植年限苜蓿草地布设田问试验，系统研究了3，6，8，10，12以及14a紫花苜蓿生产力及其土壤水分变化特征。结果表明，不同种植年限紫花苜蓿草产量差异显著，且表现为随着种植年限的增加，呈先增加后减小的趋势，其中以8a苜蓿草产量最高，为12128kg／hm^2。持续种植3，6，8，10，12和14a苜蓿草地0～300cm土层平均含水量均明显低于当地土壤稳定湿度值，其中12和14a仅为9．20％和7．14％，甚至低于作物有效水分下限。随着苜蓿种植年限的延长，土壤干燥化程度加剧，但干燥化速率呈减缓趋势。综合苜蓿生产力动态和土壤水分状况，本研究表明陇中黄土高原地区紫花苜蓿适宜的种植年限为8a。

The productivity and soil moisture of alfalfa （Medicago sativa） grassland with different years of growth （3, 6, 8,10, 12 and 14 years） were investigated in a typical semiarid area on the Western Loess Plat eau. There were significant differences in the dry matter yield from alfalfa grasslands with different years of growth. At first the dry matter yield increased, then it declined. The highest hay yield （12128 kg/ha） was found in alfalfa grassland with eight years of growth. Average soil moistures in 0-300 cm soil layers of alfalfa grasslands with different years of growth was significantly lower than local soil stable moisture （SSM）. The soil water content in grasslands with alfalfa that had been growing for twelve and fourteen years was 9.20% and 7. 14% respectively, which is even lower than the crop lower limit （CLL）. Over the years of alfalfa growth, soil desiccation intensity increases and soil desiccation rate decreases. Therefore, according to the soil moisture and productivity results produced by this study, the optimum growth period for alfalfa production is eight years in semi-arid areas of the Loess Plateau.