Effect of different greencover patterns on soil secondary salinification in Qinwangchuan irrigated area

Soil secondary salinification was caused by unreasonable irrigation and bare soil, it has already become a main obstacle of agricultural sustainable development. The spatial and temporal dynamic changes of soil salt content in bare soil, or soil growing Triticum aestivum, Onobrychis viciaefolia, and T.aestivum / Vicia villosa were studied and the difference among four patterns was compared. The results indicated that during the wheatharvest period, three growing patterns had obvious restraining salt effect in 0～20 cm soil layer, and salt content of topsoil was reduced by 16.4%～30.5%.The difference between growing wheat and O.viciaefolia and T.aestivum / Vicia villosa was significant; however, the difference between growing O.viciaefolia and growing T.aestivum / Vicia villosa was not significant. The soil salt content within 80 cm was increased by 14.2% through sowing spring wheat, but decreased by 19.7% and 23% when sowing T.aestivum / Vicia villosa and O. viciaefolia. The vertical distribution of soil salt content was higher in middlelayer (2060 cm) than in the surface (020 cm) and lower layer (6080 cm) when only growing wheat. When growing O. s viciaefolia or T. aestivum / Vicia villosa, soil salt content was lower in the surface than other layers. After spring wheat was harvested, the soil salt accumulated quickly to the surface of the land, and the salt content of topsoil was higher than that in uncovered land. If T. aestivum / Vicia villosa is implemented, it can not only restrain soil secondary salinization, but also produce more forage by 36 018 kg/hm2.