Optimizing Nitrogen Management For High-yielding Maize(Zea Mays L.) In Northwest China By Using Controlled-release Fertilizer

Increasing the yield of maize sustainability and stably with high nitrogen efficiency is essential for the food security. In order to understand the growth and development of high yield maize and we choose the spring maize in Northwest China as a case because of high yield potential (>15 Mg ha-1) in this region. Based on model simulation, high-yielding maize system (>15 Mg ha-1) was designed and tested in the filed in Ningxia and Gansu province. Dry matter and nutrient accumulation for high-yielding maize were analyzed based on field experiment data sets. The simplified N managements based on the controlled release fertilizers were studied in this areas. The main results are as follows:1. In Yongning, which located in Ningxia (irrigated area) and Zhenyuan, which located in Gansu (rainfed area), based on long-term weather data and hybrid maize model, highyielding system were designed, which include appropriate crop varieties, sowing dates, densities. Grain yield with designed crop management varied from 16.1 to 19.1 Mg ha-1, which attained 98% to 108% of the yield potential. The optimal N rate ranged from 207 to 222 kg N ha-1 with a high over ratio of 65 to 80 kg grain per kg applied N.2. A database comprising 537 measurements conducted in the spring maize with yield level over 15 Mg ha-1 which domains of Northeast, Northwest of China and North China Plain, was used to evaluate N requriment in relation to grain yield. As the yield level increased, N uptake requirement per ton grain yield stayed stabilized as 17.1 kg. The averaged grain N concentration and N harvest index were improved and straw N concentration was redued as the yield increased because of the increased of nitrogen transfer efficiency. The harvest index was kept about 0.50. Based on the 128 measurements, dry matter and N accumulation post-anthesis increased to 66% and 52%, when the yield was over 15 Mg ha-1. The N management is more important for high-yielding maize.3. In Changwu, which was film mulching in Shannxi (rainfed area), a two-year field experiment on the effects of different proportions of controlled release urea (CRU) and normal urea applied once before sowing was designed. The results showed that the treatment of N fertilizer rates of 180 kg N ha-1, with 1:2-CRU:Urea fertilizer mixture in one application could achieve high grain yields (11.8-12.0 Mg ha-1), N uptake (232-239 kg ha-1), PFPn (65.6-66.6 kg kg-1) and REN (65.8-67.7%). Moreover, the greatest net return was achieved in this treatment. These findings verify that blending CRU and urea for single basal application can facilitate simple, efficient, and economical N management.4. In Yongning, which was irrigated by yellow river, treatments factors consisted of one sole urea and two CRU-N (nitrogen from N)/Urea-N (nitrogen from N) mixtures (1:2; 2:1) applied at two N rates (180 kg ha-1 and 240 kg ha-1). The results indicated that 240 kg N ha-1 input one-off application with CRU-N proportion 1/3 mixture performed better in irrigated system, which could achieve high yields (17.8-19.3 Mg ha-1), N uptake (370-339 kg ha-1) and higher net return in both years.5. The effects of maize yield and N2O emission by applicating controlled release fertilizer were studied using methods of Data Mining. The results indicated that applying controlled release fertilizer increased the maize yield and reduced the N2O emissions, while there are variations among different amounts and soil pH.6. The comparative trial of subsoiling and rotary tillage has been established in 9 field sites which located on the northeast, north and northwest of China, to quantify the effects of subsoiling on maize yield, nutrients uptake and soil nutrients distribution in main maize-growing areas. The results showed that, maize yield was improved by the subsoiling in the three maize-growing areas by the median number 5.8%, and the yield increase in northeast and northwest were higher than in north China. The nitrogen and phosphorous uptake by maize plant during harvest had been increased in the subsoiling treatment, the median numbers of the nutrient uptake increase were 24%,5% and 10% for nitrogen and 17%,8% and 19% for phosphorus, in northeast, northwest and north China, respectively. Soil available phosphorous and potash had been improved in the surface and as well as subsurface layers (0-15 cm and 15-25 cm) in the subsoiling treatment in northeast and northwest China.