The effect of conversion of cropland to forage legumes on soil quality in a semiarid agroecosystem

This study explores the ecological restoration effects of the conversion of cropland to forage legumes on soil characteristics in the semi-arid Loess Plateau of China. Four types of treatments: fallow (F); alfalfa (Medicago sativa) forage legume (A); sweetclover (Melilotus officinalis) forage legume followed by fallow (SF) and erect milkvetch (Astragalus adsurgens) forage legume (E) were used to substitute for spring wheat, the native crop in April 2003 to October 2005. The results indicated that the highest soil water content in various soil layers was observed in F treatment during the whole experimental period, followed by SF treatments. The light fraction of organic C (LFOC) and increase of soil water content in SF was the highest. The above-ground biomass in SF was lower than that in E but higher than that in A and F. The total organic carbon (TOC) content in F and SF was higher than that in the other two treatments. But the total nitrogen (TN) content in F and SF was lower than that in A and E. Over the entire experimental period, the water use efficiency (WUE) of E was higher than that of A, SF and F by 70.02%, 42.05%, and 36.80%, respectively. In conclusion, SF proved to be a better pattern for soil productivity, soil quality, and nutrient cycling under semiand conditions.