Effects of plastic film mulching periods on the soil nitrogen availability in semiarid areas
半干旱地区不同地膜覆盖时期对土壤氮素有效性的影响

A field experiment was carried out on cultivated loessial soil in semiarid areas with 415 mm precipitation and spring wheat ( Triticum aestivum L.) used as an indicating crop to study the effects of the plastic mulching periods on the soil nitrogen availability.The experiment had three factors and they were water storage in soil profile before sowing,plastic film mulching period and nitrogen fertilization.The water storage in soil profile before sowing had two levels under each of which there were no mul...