Leguminosae herbage with deep roots such as alfalfa and sweet clover, leaves the deep soil plenty of root residue, which helps to improve the urease activity and soil fertilily of deep soil.

• 深根豆科牧草苜蓿、草木樨可留给深层土壤大量根系残留物，从而有利于提高土壤深层脲酶活性与综合供肥能力。