Research On Nitrogen Nutrition Status And Diagnosis For Various Varieties Of Winter Wheat On Dryland

The suitable application of nitrogen fertilizer not only affects the yield and quality of wheat, but also the safty of the environment. And a lot of researches have been carried out in these aspects. However, many of the researches have concentrated on the areas with higher application of water and nutrients. There is limited information available on the uptakes, accumulations and translocation of nitrogen for the different varieties on dryland regions of China. This is also true for nitrogen diagnosis of winter wheat on dryland. Therefore, the field experiment was carried out to research the nitrogen nutrition status and diagnosis for various varieties of winter wheat on the dryland. The main results were shown as followings:(1) The curve of dry matter accumulation could be divided into three phases, i.e., exponential increasing phase, liner increasing phase and slowly increasing phase. Nitrogenous fertilizer increased the dry matter accumulation and grain yield of winter wheat. The dry matter and grain yield increased with the increase of N rate when the N rate is less than 180 kgN/hm2; they were decreased by higher nitrogen application. The biological and grain yield of Xiaoyan22 varieties were higher than that of the three other varieties; the dry matter and grain yield were in the following order, Xiaoyan22 >Xiaoyan503>Shaan253>Shaan229. Compared to the other grain components of winter wheat, the number of spike per ha had the biggest contribution to the yield.(2) The higher stages of N accumulation in the growth period were in Jointing stage and Anthesis stage. The highest N accumulation for leaf and stem was in Jointing stage and Anthesis stage, respectively. The N transportation rate of leaf was 80%. The N transportation rate of stem was 40-50%. Xianyan22 varieties had the highest N transportation of leaf and stem.(3) The application of nitrogen fertilizer had the significant effects on the N use efficiency and N harvest index. The N use efficiency and N harvest index was the highest for the treatment without N addition; and as the increasing N rate, there was a declining trend for N use efficiency and N harvest index. The N harvest index did not show obvious differences among different varieties, but the N use efficiency had difference. The recovery of nitrogen fertilizer, nitrogen agronomic efficiency and nitrogen physiological efficiency had declined with the increasing N rate. There was significant difference between Xiaoyan22 and the other varieties. (4) In Jointing stage, NO3--N, NH4+-N, NH2--N(amide nitrogen,NH2--N), Pro--N (soluble protein nitrogen, Pro--N) showed obvious differences among the different varieties. The significant correlationships were found between NH4+-N, NH2--N, Pro--N and yield and N rate. In vegetable growth stage, the yield increased with the levels of NH4+-N, NH2--N, Pro--N in the leaves of wheat. The optimum stage for nitrogen diagnosis was in the Jointing stage.(5) The significant correlationships were found between the readings (SPAD value) of chlorophyII meter and the yields of biomass and grain of winter wheat, especially at jointing stage and anthesis stage. The SPAD value and the application levels of nitrogen also had a close correlation, the SPAD value was the highest under 180 kg/hm2 of nitrogen rate. In the same application levels of nitrogen the SPAD value was the highest at anthesis stage. The variations of the SPAD value with the variety of wheat were less before jointing stage; and after jointing stage the variations of the SPAD value were increasing. The highest variation of the SPAD value was 9.2 SPAD unit for different varieties of winter wheat. Xiaoyan22 had the highest SPAD value at every stage, was higher than that of Shaan253 Shaan229 and Xiaoyan503. Therefore, Xiaoyan22 was a different type of cultivars. The variations of SPAD value with the variety of wheat is needed considering during the nitrogen diagnosis.