Nitrogen In-season Management For Winter Wheat And Summer Maize

Excessive application of N fertilizer is the main problem of winter wheat and summer maize cropping system in North China Plain. It is important to ensure the crop yield, increase nitrogen use efficiency and reduce environmental pollution by studying the laws of biomass and nitrogen accumulation of the main cultivars in North China and applying nitrogen fertilizer according to the crop demand in different stages combined with the content of soil initial inorganic nitrogen and indigenous nitrogen supply (INS). Therefore, field experiments were conducted with the materials of winter-wheat Hengguan 35 and summer maize Zhengdan 958. Combined with soil testing and plant analysis, the application effect on winter wheat and summer maize with different nitrogen management practices were compared and the scientific methods of nitrogen synchronous regulation were explored. The major findings are as following:1 The laws of dry matter and nitrogen accumulation of winter wheat in different fertility soils were revealed. The findings showed that the peak of dry matter accumulation of winter wheat was from jointing to heading and from heading to filling, while the peak of nitrogen accumulation was found to be from jointing to heading. The highest dry matter and N accumulation rates in different stages of winter wheat could be improved and its earlier occurring could be achieved with basal nitrogen fertilizer.2 The soil Nmin content and indigenous nitrogen supply of Hengshui experiment site, which belongs to high fertility site, were higher than that of Xinji experiment site. There is no significant effect to biomass and nitrogen accumulation of winter wheat before regreening with basal nitrogen fertilizer or not. The loss of nitrogen in winter wheat was mainly occurred before jointing. Therefore it would be beneficial to improve wheat yield, increase nitrogen use efficiency and reducing the loss of nitrogen by topdressing properly after jointing.3 A significant or highly significant relationship was found between leaf SPAD readings of key growth stages in winter wheat and the leaf nitrogen content, and the correlation in late growth stage was higher than that of prophase. The correlation between SPAD reading and Na was higher than Ndw. Therefore the status of plant nitrogen could be reflected by SPAD readings.4 The peak of dry matter and nitrogen accumulation of summer maize was from jointing to heading. The highest rates of dry matter and nitrogen accumulation in different growth stages of summer maize were increased with the amount of nitrogen. The occurrence of the highest accumulation rate would be achieved earlier with the increase of basal fertilizer.5 The soil Nmin content and indigenous nitrogen supply of Hengshui experiment site were higher than that of Xinji experiment site in summer maize season. Nitrogen fertilizer with split application can not only increase yield and nitrogen use efficiency, but also reduce the soil Nmin residual and its apparent loss, and synchronize N demand of maize in different growth stages and soil N supply. Compared with FFP (Farmers'Fertilizer Practice), 25%-85% amount of fertilizer could be saved by nitrogen fertilizer with split application. The nitrogen application effect could be significantly affected by the difference of soil fertility and texture. Therefore, regionalized N management should be adopted in nitrogen management practices combined with the demand of crop nutrient in different stages and soil supplying nutrient capacity.6 A significant or highly significant relationship was found between leaf SPAD readings of key growth stages in summer maize and the leaf nitrogen content. The correlation between SPAD readings and Na was higher than Ndw, therefore the status of plant nitrogen could be reflected by SPAD readings.