| Corn has become China's first staple type. Guanzhong plain is the main area of summer maize production in Shaanxi Province. The production of summer maize local is pretty important to the food security of the whole province. The production of summer maize is highly dependent on water and nutrient supply. However, water and nitrogen supply in this region is limited. With nitrogen fertilizer increasing, yield of summer maize can be improved.But it will lead to the environmental pollution, waste of resources caused by nitrogen losses and ammonia volatilization. Conservation tillage practices has attracted wide attention recent years because it can protect environment and increase yield. But the effects of conservation tillage vary owing to climate condition and soil fertility. Experiment was conducted in Yangling, Guanzhong Plain during the 2014 and 2015 summer maize growing season. Effects of different conservation tillage and nitrogen treatments on the growth, water and nitrogen utilization of summer maize were studied. The field experiment is in a split-plot design, three conservation tillage methods, namely rotary and ridge tillage(RT), no-tillage(NT) and no-tillage with straw mulching(NTM) were assigned to the main plot and nitrogen(N230 and N0) applications were the subplot. There are 6 trials which are repeated 3 times. The grain yield, water and nitrogen utilization, ammonia volatilization and available nitrogen residue,soil environment factors of summer maize under different tillage and nitrogen treatments were analyzed to find a suitable conservation tillage and provide the theoretical basis for summer maize planting, improvement of water and fertilizer utilization. The main results are listed as follows:(1)Tillage and fertilization had a significant effect on grain yield and its components of summer maize(P< 0.05).NT and NTM treatments could increase grain yield, 100 kernel weight and ear kernel number of summer maize significantly(P< 0.05).The average grain yield during the 2014 and 2015 growing seasons of three conservation tillage practices showed as NTM > NT > RT. Grain yield averaged 6002 kg ha-1 and 6792 kg ha-1in NT and NTM treatments, 25.3% and 41.8% respectively greater than RT(4789 kg ha-1). In addition,nitrogen application could significantly increase grain yield(P< 0.05).The average grain yield of N230(7024 kg ha-1) increased by 49.5%(P< 0.05) than N0 treatment(4698 kg ha-1).(2) Tillage and nitrogen treatment could significantly affect the water storage and wateruse efficiency of summer maize(P< 0.01). Compared with RT, NT and NTM treatments could significantly reduce the water consumption of summer maize, and increase water use efficiency and water storage of 0 ~ 2 m soil layer after harvest(P< 0.05). Water use efficiency in NT and NTM treatments averaged 23.6 kg mm-1 ha-1and 26.8 kg mm-1 ha-1respectively,42.4%and 62.0%greater than RT treatment(16.5 kg mm-1 ha-1, P< 0.05). Nitrogen application could increase the water consumption and water use efficiency of summer maize, and decrease the soil water storage(P< 0.05). Water use efficiency of N230 application averaged26.8 kg ha-1 mm-1, compared to the treatment N0 application(17.8 kg ha-1 mm-1),which is increased by 50.5%(P< 0.05).(3) Tillage could significantly affect nitrogen uptake and nitrogen use efficiency(P<0.01). Compared with RT, NTM could significantly improve the nitrogen uptake and nitrogen use efficiency(P< 0.05), reduce vegetative organ nitrogen translocation amount and efficiency,vegetative organ nitrogen contribution ratio. There was no significant difference of nitrogen harvest index between RT and NTM treatment. Nitrogen use efficiencyin NT and NTM treatments averaged 26.8% and 33.1% respectively, which were both higher than RT(23%).Nitrogen fertilization could increase the amount of nitrogen uptake(P< 0.05) and vegetative organ nitrogen translocation, but it would reduce vegetative organ nitrogen translocation efficiency, vegetative organ nitrogen contribution ratio and nitrogen harvest index. Nitrogen uptake in N230 application averaged 121.8 kg ha-1, which was significantly higher than N0application(58.3 kg ha-1)(P< 0.05).(4) The effect of tillage treatments on soil ammonia volatilization was not significant,and the loss of ammonia volatilization was significantly affected by nitrogen application(P<0.01). The soil ammonia volatilization peak appeared on sixth days after the jointing stage fertilization. There was no difference of soil ammonia volatilization loss between tillage treatments. However, NT and NTM treatments could reduce ammonia volatilization loss from nitrogen fertilizer in a certain extent. In addition, during the 2014 growing season with more precipitation, NT and NTM treatments increased the nitrate leaching. Nitrogen fertilization could improve soil ammonia volatilization loss and nitrate nitrogen residue in soil profile significantly. Among them, the average application soil ammonia volatilization loss and nitrate nitrogen residue of N230 application were 3.48 kg N ha-1 and 585.24 kg N ha-1respectively, which were significantly higher than N0 application(2.37 kg N ha-1 and 64.85 kg N ha-1,P< 0.05).(5)The dynamic changes of soil environmental factors in different tillage and nitrogen treatments during summer maize growth period were different. NT and NTM treatments were more favorable to the stability of soil environmental factors. Compared with RT treatment,fluctuation range of soil moisture, temperature, p H, nitrate and ammonium content during growth period in NT and NTM treatments were smaller. Nitrogen fertilizer application has no significant effects on soil moisture and temperature. But the content of available nitrogen increased by nitrogen fertilization, and the nitrogen fertilizer application presented a trend of soil acidification. In the soil of N230 applications, the p H decreased, nitrateand ammonium increased.In general, in the local climatic conditions, no-tillage with straw mulching(NTM) can increase grain yield, water and nitrogen use efficiency of summer maize, reduce the ammonia volatilization loss from fertilizers to a certain extent. Therefore, no-tillage with straw mulching(NTM) is recommended in summer maize planting area of Guanzhong Plain. |
PDF Full Text Request