陇中黄土高原半干旱区苜蓿地土壤干燥化特征及适宜种植年限

研究了陇中黄土高原半干旱区不同种植年限紫花苜蓿地土壤水分特征及适宜种植年限.结果表明： 3、8、12和14年生苜蓿地0～300 cm土层土壤平均含水量均明显低于当地土壤稳定湿度值.12和14年生苜蓿地0～300 cm土层土壤含水量仅为9.2%和7.1%，甚至低于作物有效水分下限.1、3、8、12和14年生紫花苜蓿地0～300 cm土层干燥化指数分别为125.4%、30.5%、18.4%、-34.2%和-83.3%，除1年生苜蓿地土壤无干燥化现象之外，其余种植年限苜蓿地土壤均呈不同程度的干燥化.随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，该区紫花苜蓿适宜的种植年限为8～10 年.

Soil dryness characteristics of alfalfa cropland and optimal growth years of alfalfa on the Loess Plateau of central Gansu,China.

This paper investigated soil moisture in alfalfa (Medicago sativa) cropland with different growth years (1, 3, 8, 12 and 14 years) and discussed the optimum growth years of alfalfa on the Loess Plateau of central Gansu. The results showed that the soil moisture along 0-300 cm soil profile of alfalfa croplands with different growth years was obviously lower than that of the local soil stable moisture. The soil water contents in croplands with alfalfa that had grown for 12 and 14 years were only 9.2% and 7.1% of local soil stable moisture, respectively, which were even lower than the lower limit of alfalfa growth. The average soil dryness indexes along 0-300 cm soil profile in 1, 3, 8, 12 and 14 years alfalfa croplands were 125.4%, 30.5%, 18.4%, -34.2% and -83.3% respectively. The results indicated that soil dryness occurred to varying degrees with different growth years except croplands with alfalfa grown for 1 year. With the increase of growth years of alfalfa, the soil dryness intensity increased and the soil dryness rate decreased. According to the soil moisture and alfalfa productivity results in this study, it could be concluded that the optimum growth years of alfalfa are 8-10 years in semi arid areas of the Loess Plateau.