Effects Of Irrigation And Nitrogen Fertilizer On Wheat Growth Under Straw Mulch In Dryland

Straw mulch is one of the most important cultivation technology in arid zones of Northern China. It can improve capacity of water storage, water retention and water supply in soil, leading to increase of crop yield in many areas. But some researches indicate that crop yield under straw mulch was as same as that of no mulch, or even straw mulching reduced yield significantly. Aiming at the problem, filed experiments were carried out to investigate the effect of irrigation and N fertilizer on wheat growth under straw mulch in dryland in order to find out the relationship between irrigation time, N rate and yield of wheat, water and fertilizer use efficiency. The main results obtained were listed as follow:1. When 40mm supplementary irrigation was allied during jointing stage or filling stage of winter wheat, straw mulch increased wheat yield due to the improvement of grain number per spike. However, straw mulch didn't increase wheat yield when irrigation was applied during seedling stage, over-winter stage of winter wheat, or no supplementary irrigation was plied.2. When 40mm supplementary irrigation was allied during jointing stage or filling stage of winter wheat, straw mulch also increased N uptake by wheat. When irrigation was applied during over-winter stage or jointing stage, residual nitrate in soil depth of 0^-200cm under straw mulch was less than that of no mulch treatment, while the opposite was true when irrigation was applied during filling stage. Under straw mulch, supplementary irrigation during any growth stage of wheat caused increase of residual nitrate in soil compared with no irrigation treatment.3. When supplemental irrigation was applied during the earlier growth stage of wheat, straw mulch was beneficial to water storage in soil. When supplemental irrigation was applied during the later growth stage, straw mulch was beneficial to improvement of water use efficiency.4. When 40mm supplementary irrigation was applied during over-winter stage of wheat, straw mulch didn't increase wheat yield in range of 0³00 kg N / hm². N rate required by the maximum wheat yield under straw mulch was higher than that for no mulch. Tiller number and spike number of wheat under straw mulch was less than no mulch. The opposite was true for grain number per spike of wheat. 5. Under straw mulch, N uptake by winter wheat increased with the increase of N rate. Residual nitrate in soil depth of 0^-200cm didn't increased significantly when N rate increased from 0 to 150kg·hm^-2, while much nitrate was found though the soil profile when more than 150 kg·hm^-2 nitrogen fertilizer was applied. The peak of accumulated nitrate under straw mulch appeared at the soil depth 40 cm deeper than that of no mulch.6. No significant difference of soil water water consumption was found between straw mulch and no mulch. However, water use efficiency of winter wheat for straw mulch was lower than no mulch. When 150 kg·hm^-2 N was applied, the highest water use efficiency was obtained under straw mulch...