Effects Of Long-term Nitrogen Fertilization Combied With Straw Mulching On Wheat Growth And Soil Property In Dryland

Straw mulching is an important measure to improve soil water storage and fertilities. It has been widely used in the dryland of northern China. However,some researchers reported that application of mulching restrained the subsequent crop growth,which could even result in yield reduction. What is the effect of mulching on wheat growth in the dryland of southern Loess Plateau? Is there interaction between nitrogen fertilizer and straw mulching in this area? A long term experiment in Yangling was used to investigate the effects of mulching and nitrogen fertilizer on winter wheat growth,yield,water and fertilizer use efficiency,and soil properties. Here showed the main results:1. Straw mulching decreased the tillers number per wheat in winter and stems number per hectare in spring, which further resulted in less spike numbers per hectare and yield compared with no mulching treatment. For both of straw mulching and no mulching, application of nitrogen fertilizer promoted wheat growth and yield. Straw mulching treatments could obtain the highest yield when N rate was 274 kg/hm2 while no mulch could obtain the highest yield when N rate was 226 kg/hm2.2. Compare with no mulch,straw mulching improved soil temperature during winter period, but reduced soil temperature during the other growth periods. Straw mulching treatments had significantly less difference between maximum temperature and minimum temperature in a day than no mulch treatments.3. Straw mulching significantly increased organic matter content of 0-20 cm soil and water storage in 0-200 cm soil profile while it didn’t influence soil total nitrogen, available phosphorus, available potassium content and WUE. When nitrogen fertilizer rate was less than 225 kg/hm2,straw mulching reduced soil nitrate nitrogen accumulation in the 0-200 cm soil profile compared to no mulch. When nitrogen fertilizer rate was less than 150 kg/hm2, straw mulching increased soil microbial biomass carbon and nitrogen. Excessive N application significantly increased the residual nitrate nitrogen in 0-200 cm depth of soil,but had no impact on soil organic matter, total nitrogen, available phosphorus and available potassium content. NUE decreased with the increasing N rate.Straw mulching increased soil water storage and organic matter content while it couldn’t increase wheat yield in summer fallow-winter wheat system. Thus, straw mulching was not recommended in this area.