关键词: 黄土高原, 半湿润区, 紫花苜蓿, 土壤干燥化, 草粮轮作, 水分恢复

Abstract:

【Objective】 Soil desiccation in alfalfa fields and the effects of alfalfa-grain crop rotation on soil water restoration of desiccated alfalfa fields in semi-humid areas of the Loess Plateau were studied. 【Method】 Soil moisture of alfalfa fields with different alfalfa-growing years and various alfalfa-grain crop rotation fields were observed at Zhenyuan Station of Gansu province, and the characteristics of desiccated soil layers of alfalfa fields and the effects of soil water restoration by alfalfa-grain rotation were analyzed.【Result】 The average soil moisture in the 0-1 000 cm soil layers of 15-28-year alfalfa fields was 10.20%, soil desiccation rate was 34.2 mm per year and the maximum distribution depth of desiccated soil layer was over 1 400 cm. Soil moisture in desiccated soil layer of alfalfa fields could be restored gradually after alfalfa plowed out and rotated with grain crops for 3-25 years, the average thickness of moisture restored soil layers was 583 cm, and the average rate of soil water resumption was 77.3 mm per year, and the average soil water restoration index (SWRI) reached 83.3%. To restore soil water to local soil stable moisture (15.5%) in 15 alfalfa-growing years field by alfalfa-grain crops rotation at least 8 years are needed. 【Conclusion】 The suitable alfalfa-grain crops rotation pattern for soil water restoration is “10 year alfalfa rotated with grain crops for at least 8 years”.

Key words: Loess Plateau, semi-humid area, alfalfa (Medicago sativa L.), soil desiccation, alfalfa-grain crop rotation, soil water restoration