Effects Of Irrigation And Nitrogen Fertilization On Winter Wheat Yield, Wue, Nue And Soil Temperature Under Straw Mulching

Natural resources such as photo-thermal energy and large arable lands abound in dry land of China. Straw mulching is one of the important measures to improve crop production in this area. Many studies showed that straw mulching could improve soil water conservation and supply, as well as improve crop yields. However, some studies suggested crop yields under straw mulching may depend on soil water and nutrients supply. A 6-years field experiment was conducted to investigate the effects of irrigation time and N rate on winter wheat growth, WUE, NUE, soil temperature and soil fertility under straw mulching. Here the last two years results were reported.1 Limited irrigation in different growth stage of winter wheat effected on wheat growth under straw mulching. Straw mulching had different impact on wheat yield in the last two years. It may result from water storage in 0-200 cm of soil before wheat sowing. Irrigation at jointing stage treatments had greater wheat yield compared with other treatments no matter straw mulch was applied. Irrigation at jointing stage treatment and irrigation at seed-filling stage treatment had greater water use efficiency (WUE) compared with other treatments when no much was applied. However, irrigation at seed-filling stage treatment had greater WUE compared with other treatments under straw much. The distribution trend of nitrate through 0-200 cm soil profile was not influenced by straw mulch or irrigation. More nitrate stayed in the upper 60 cm of soil depth after wheat harvest. Nitrate content below 60cm of soil was lower and did not change a lot with the soil depth. Under straw mulch, irrigation during wheat growth period could reduce nitrate accumulation in soil.2 Straw mulching and irrigation at over-winter stage of wheat had significant impact on soil temperature. Compared with no irrigation treatment, irrigation in overwintering stage of wheat decreased soil temperature. Regardless of straw mulch or no-mulch, soil temperature of 20 cm depth was higher than that of 10 cm from 0 to 12 pm while the reverse was true after 12 pm. Straw mulch treatments had higher soil temperature compared with no mulch during overwintering stage. Straw mulch treatments had lower soil temperature from 0 to 12 pm and higher soil temperature after 12 pm compared with no mulch during overwintering stage. However, straw mulch didn't influence soil temperature during turning-green and jointing stages. Straw mulch treatments had lower soil temperature from 0 to 12 pm and higher soil temperature after 12 pm compared with no mulch during heading and seed-filling stages. Straw mulching reduced soil temperature diurnal amplitude, as well as soil heating rate and cooling rate.3 Effects of straw mulching on wheat growth depended on N rate. When no nitrogen or low nitrogen fertilizer was applied, straw mulch treatment and no mulch treatment had similar wheat yield. However, straw mulch treatment had lower wheat yield than no mulch. N225, N300 had greatest wheat yield, and N225 also had greatest WUE compared with other treatments, suggesting that ample N fertilizer was a key factor to improve wheat yield and WUE. Straw mulch reduced nitrogen use efficiency (NUE). N150 had highest NUE regardless of straw mulch or not. When less N fertilizer was applied, straw mulch treatment had greater nitrate accumulation in 0-200cm soil depth than that of no mulch while the reverse was true for high N rate treatments. N225, N300 had significant greater nitrate accumulation in soil profile regardless of straw mulch or not. There was great difference of nitrate content through 0-200 cm soil depth between low N rate treatments and high N rate treatments. However, great difference of nitrate content was only found in deeper layer of soil. Straw mulch treatments had slight higher organic matter content and total nitrogen content in surface layer of soil compared with no mulch.