黄土高原半湿润区苜蓿草地土壤干燥化与草粮轮作水分恢复效应

Soil Desiccation of Alfalfa Fields and Effects of Alfalfa-Grain Crop Rotation on Soil Water Restoration of Desiccated Alfalfa Fields in Semi-Humid Areas of the Loess Plateau

【目的】揭示黄土高原半湿润区苜蓿草地土壤干燥化发生规律与草粮轮作对干燥化苜蓿草地土壤水分恢复效应。【方法】在甘肃镇原试验站实地测定了不同生长年限苜蓿草地与不同类型草粮轮作粮田深层土壤湿度,分析了苜蓿草地土壤干层分布特征与草粮轮作对土壤干层水分恢复效应。【结果】15—28年生苜蓿草地0—1000cm土层土壤湿度平均值为10.20%,土壤干燥化速率为34.2mm·a-1,土壤干层最大分布深度超过了1400cm;苜蓿草地翻耕并轮作3—25年粮食作物后土壤干层湿度能够逐步恢复,土壤干层恢复厚度为583cm,土壤湿度恢复速率为77.3mm·a-1,土壤湿度恢复度达到83.3%。通过草粮轮作方式使15年生苜蓿草地土壤湿度恢复到当地土壤稳定湿度值需要8年以上。【结论】有利于土壤水分恢复的适宜草粮轮作模式是"10年生苜蓿→8年以上轮作粮食作物"。

【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＂.