氮肥施用对四川紫色土矿质态氮淋失特征及春玉米产量的影响

为探究不同施氮量下春玉米季土壤矿质态氮淋失特征及产量变化,以春玉米为研究对象,设置不同施氮量(0、90、180、270、360 kg·hm-2,分别用N0、N90、N180、N270、N360表示),采用地下淋溶原位监测的方法,测定了玉米生育期间的土壤氮素淋失动态、玉米产量及氮肥利用率.结果 表明:硝态氮(NO-3-N)是春玉米季旱地土壤矿质态氮淋失的主要形态,占总淋失量的90％～91％;施用基肥和苗期追肥后1～3周出现氮素淋失高峰,是防控氮素淋失的关键时期;随施氮量增加,矿质态氮淋失量呈指数上升趋势,表现为N360(70.46 kg·hm-2)>N270(39.65 kg·hm-2)>N180(26.33 kg·hm-2)>N90(18.55 kg·hm-2)>N0(6.54 kg·hm-2),各处理间差异达显著水平(P<0.05).氮肥表观淋失率随施氮量增加呈先降后升趋势,在N180处理下,淋失率最低,为10.99％,较N270、N360处理分别降低1.27、6.76个百分点;玉米籽粒产量先随施氮量增加而显著提高(P<0.05),施氮超过180 kg·hm-2后进入平台期,N180处理下氮肥表观利用率达到最高,较其他处理增加14.50～27.75个百分点.总体来看,该研究区域春玉米的最佳施氮量为180 kg·hm-2,既能稳产也能保肥,同时土壤的氮素淋失率最低.

Effects of nitrogen application on the characteristics of mineral nitrogen leaching in purplish soil and spring maize yield in Sichuan

The aim of this study was to explore the effects of different nitrogen(N)applications on the characteristics of soil mineral nitrogen leaching during spring maize season and changes in maize yield. A field experiment was carried out with five different N applications(0, 90, 180, 270, and 360 kg·hm^-2, represented by N₀, N₉₀, N₁₈₀, N₂₇₀, and N₃₆₀, separately), using spring maize as the test material. Soil N leaching dynamics during maize season were measured by underground leaching in-situ monitoring, and spring maize yield and N fertilizer utilization efficiency were analyzed. The results showed that nitrate(NO₃^--N)was the main form of mineral N leaching in upland soil during spring maize season, and accounted for 90%~91% of the total mineral N loss. Nitrogen leaching peak occurred 1~3 weeks after base fertilization and top fertilization at the seedling stage, which was the key period to take measures to prevent N leaching. Significantly different effects on mineral N leaching were found between different N application rates. The leaching of mineral N increased exponentially with increased N application, following this order: N₃₆₀(70.46 kg·hm^-2)>N₂₇₀(39.65 kg·hm^-2)>N₁₈₀(26.33 kg·hm^-2)>N₉₀(18.55 kg·hm^-2)>N₀(6.54 kg·hm^-2). The apparent N leaching rate first decreased and then increased with increased N application. The minimum N apparent leaching rate was 10.99% under N₁₈₀ treatment, which was reduced by 1.27 and 6.76 percentage points compared with those of N₂₇₀ and N₃₆₀ treatments, respectively. The grain yield of maize significantly increased with increasing N application(P < 0.05)and then reached a plateau stage when the N rate exceeded 180 kg · hm^-2. The apparent use efficiency of N fertilizer reached the maximum under N₁₈₀ treatment, which increased by 14.50~27.75 percentage points compared with other treatments. In conclusion, the application of 180 kg · hm^-2 could be considered the optimum N rate to obtain stable maize grain yield, maintain fertility, and achieve the lowest soil mineral N losses in the study area, ensuring stable yield and saving fertilizer.