灌水次数对绿洲春玉米田氮素损失及水氮利用效率的影响

Effect of irrigation times on nitrogen loss, water and nitrogen use efficiencies in oasis spring maize farmland

该文研究灌水次数对绿洲农田氮素损失及水氮利用效率的影响。2015年在甘肃省武威市石羊河流域绿洲农田设置了5种灌溉施肥处理:分别为传统施肥(N_1)+传统灌水4次处理(I_1N_1),优化施肥(N_2)+优化灌水4~7次处理(分别为I_2N_2、I_3N_2、I_4N_2和I_5N_2)。应用农田水氮管理模型(soil water heat carbon and nitrogen simulator,WHCNS)模拟分析了不同灌水次数下的作物产量、水氮动态过程及水氮利用效率,最后应用综合指数法筛选了农田最佳的水肥管理方案。结果表明:模型模拟的土壤含水率、土壤硝态氮含量、作物产量和叶面积指数与实测值均吻合良好,一致性指数在0.74及以上。5个处理中I_3N_2处理的春玉米产量、水分和氮素利用效率均最高,分别为17 077 kg/hm^2、3.23 kg/m^3和40.1 kg/kg。I_1N_1处理的水分渗漏和硝态氮淋失量均最大,而I_5N_2处理的最小。在灌溉定额一定的条件下,随灌水次数增加,水分渗漏量逐渐减少,同时硝态氮淋洗和氨挥发也逐渐减少,而反硝化和作物吸氮量逐渐增加。综合指数法评价结果表明I_3N_2处理为该地区最佳的水肥管理方案。因此,在该地区适当增加灌水次数和减少单次灌水量,不仅可以维持作物产量不变,而且显著减少了水分渗漏和氮素淋洗,同时提高了水氮利用效率。结果可为荒漠绿洲地区制定合理的水肥管理措施提供指导。

Exploring the effects of different irrigation times on nitrogen（N）loss,and water and N use efficiencies（WUE,NUE）of spring maize in desert oasis can provide advice for the establishment of rational water and fertilizer management measures in desert oasis.In this study,we investigated the effect of irrigation times on farmland N loss,crop yield and water and nitrogen use efficiency.A field experiment was conducted in the basin of Shiyang river,Gansu province in 2015.The soil was loam with obvious layers.A total of 5 different water and fertilizer combined practices were designed and they included 1conventional fertilizer and irrigation treatment I_1N_1（4 irrigation events）and 4 optimal fertilizer and irrigation treatments：I_2N_2（4 events）,I_3N_2（5 events）,I_4N_2（6 events）and I_5N_2（7 events）.The total irrigation amount of conventional and optimal treatments was 480 and 420 mm,respectively.The fertilization rate of the conventional and optimal treatment was 280 and 200 kg/hm^2,respectively.Each treatment replicated 3 times.The spring maize was planted in April in 2015.A soil Water Heat Carbon and Nitrogen Simulation（WHCNS）model was used to simulate the crop yield,water and N dynamic process,water use efficiency（WUE）and nitrogen use efficiency（NUE）under different treatments.The conventional treatment was used for model calibration and the other 4 treatments were used for model calibration.Then,an integrated index method was employed to obtain the best management practices（BMPs）.The results showed that the simulated soil water content,soil NO_3^--N content,crop yield and the leaf area index agreed well with the measured values.The root mean square error（RMSE）of soil water content was closer to 0.The RMSE of soil NO_3^--N content was 4.32 mg/kg and above and the RMSE of leaf area index was0.26 m^2/m^（2 ）and above.The agreement index ranged from 0.74 to 1.The effects of irrigation times on soil moisture and nitrogen leaching were further studied based on the model simulation.The simulation showed that the optimal irrigation times could reduce water drainage.Compared to the conventional treatment,the optimal treatment decreased the drainage from 67 to24-44 mm.In addition,the increasing the irrigation times could reduce the evaporation and N leaching.Among the 5treatments,the crop yield,WUE and NUE of I_3N_2 treatment were the highest,with the values of 17 077 kg/hm^2,3.23 kg/m^3and 40.1 kg/kg,respectively.The amounts of water drainage and N leaching for I_1N_1 were the highest,while they were the lowest for I_5N_2.When the irrigation amount is given,with the increase of irrigation times,the amount of water drainage decreased slowly,the amounts of N leaching and ammonia volatilization decreased gradually,while the amounts of denitrification and crop N uptake gradually increased.The results of integrated index evaluation method indicated that the irrigation 5 times with the total irrigation amount of 420 mm was the BMPs under the specific weather condition in the study areas.We concluded that increasing irrigation frequency and reducing the amount of single irrigation cannot only maintain high crop yield,but also reduce water drainage and N leaching,and meanwhile improve WUE and NUE significantly.