| This study probed nitrogen split application issue of spring maize in Hexi Irrigation District,making the effects of nitrogen split application on dry matter and nitrogen uptake and distribution of spring maize to be understood. We selected Jin Kai NO.3 as experimental martial, set the total nitrogen application rate were 300 and 375, five nitrogen split ratios, mulching and no mulching,summed up to eight treatments(total nitrogen application rate, mulching or not, nitrogen split application ratio) Respectively, N1(300, M, 2: 4: 4), N2(300, M, 3: 2.5: 2.5), N3(300, M, 4: 3: 3),N3(300, NM, 4: 3 : 3), N4(300, M, 5: 2.5: 2.5), N5(300, M, 7: 1.5: 1.5), N6(375, M, 4: 3: 3), N7(0, M, 0), each treatment was repeated 3 times. We measured the dynamic growth index of spring maize, dry matter accumulation in various organs and nitrogen absorption at different growth stages, we researched nitrogen management on spring maize growth, dry matter accumulation distribution, the cumulative distribution of nitrogen and the impact of the nitrogen utilization. The purpose of this study is aimed at provide a theoretical basis for spring maize nitrogen rational application in Hexi irrigation District.The main results are as follows:1. It has significant improvement of grain yield after two years field experiment(2014 and2015), we can clearly understand from the table 3-12, we can conclude from the two years experimental result that the grain yield has improved 83%-142% compared with the CK treatment without nitrogen application.2. The results in 2014 showed, the grain yield of all mulching treatments except the CK had significantly improved, grain yield increased with the nitrogen application rate increasing. Under the 300 kg N ha-1 application rate and plastic mulching, nitrogen split application had no significant improvement in grain yield. The results in 2015 showed some difference, under the same condition, when the proportion of nitrogen-based applied higher than 40%( N3,N5,N6), the grain yield had significantly improved compared with the no mulching treatment(N3-NM).We can concluded from the results in 2014 and 2015, the optimal nitrogen application rate is and the suitable proportion of nitrogen-based applied range from 40% to 70% under ridgemulching-furrow irrigation in Hexi irrigation District.3. The grain yield of all treatments in 2014 higher than in 2015. The decreased accumulative temperature(≥15℃) in 2015 was one of the main reasons affecting the maize yield formation and nitrogen absorption. The grain yield after flowering in2014 mainly comes from dry matter synthesis, then in 2015 mainly from dry matter synthesis and vegetative organs transport. We can summarize from the result that the higher proportion of nitrogen-based applied contribute the dry matter and nitrogen transport from vegetative organs to grain then produce higher grain yield.4. The 15 N isotope micro test showed that it has no significant difference between the treatments with the same application rate 300 kg ha-1 and different spit application ratio, the NUE ranges from 54.8% to 63.6%. The NUE of base fertilizer ranges 47.1% to 54.7%, jointing fertilizer ranges 60.1% to 63.6%, booting fertilizer varies 60.5% to 70.1%. The NUE will lower and the nitrogen loss ratio will escalate if continue to increase to nitrogen application rate. |
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