苜蓿轮作农田和常规农田的作物产量与土壤水分及营养质量差异

Field experiment was carried out to further clarify the changes of soil water, nutrient and crop productivity to the conversion cropland from perennial M. sativa grassland in the semiarid area of China's Loess Plateau in 2010 and 2011. The field was grown for alfalfa for 30-years, before it was converted to cropland. Four treatment s were established in the experiment, 1) MF: conversion cropland with fertilized；2)MO: conversion corpland without fertilized; 3) NF: convention cropland with fertilized；4) NO: convention cropland without fertilized. The results showed that the soil water content of conversion cropland in 0-200 cm soil depth had only 78% of convention cropland in April 2010，significantly lower than the convention cropland, after two growth seasons，in September 2011，the soil water content of MO in 0-200 cm soil depth had reached to 82.80% of NO, and the soil water content of MF in 0-200 cm soil depth had reached to 89.78% of NF, and the soil water content in 0-60cm soil depth of conversion cropland had more water restoration than those of convention cropland. The conversion cropland had more total nitrogen content in 0-60cm soil depth than convention cropland in both of October 2010 and October 2011. The yields of conversion cropland were significantly lower than conventional cropland in the two years. Conclusion: Soil water content had declined severely after M. sativa grassland was grown for 30 years, which induced the reduction of crop yield follow-up, but crop rotation could improve the soil water content, which was benefit for the sustainable development of farmland system.