传统和优化施氮对春玉米产量、氨挥发及氮平衡的影响

【目的】本文通过在陕西省长武县(CW)和吉林省梨树县(LS)的春玉米田间试验,研究了传统和优化施氮对春玉米产量、土壤氨挥发及氮平衡的影响,以探讨春玉米氮肥优化的潜力及其对农田氨减排的效果。【方法】试验设对照、传统施氮(长武N 250 kg/hm2,梨树N 300 kg/hm2)及优化施氮(N 200 kg/hm2)3个处理,分别以N0、Ncon、Nopt表示。氨挥发采用德尔格氨管法(简称DTM法)进行原位测定,通过田间气象因素的校正计算氨挥发累积量。【结果】长武和梨树点不同施氮处理下春玉米的产量结果表明,除对照(长武7.9 t/hm2、梨树3.8 t/hm2)外,传统和优化施氮处理间均无显著差异(长武10.6 10.8 t/hm2,梨树9.5 9.6 t/hm2)。玉米氮肥利用率表现为优化施氮(44.3%44.5%)显著高于传统施氮(33.6%36.4%),其中长武点氮肥利用率提高了8.1个百分点,梨树点氮肥利用率增加了10.7个百分点。氨挥发田间监测结果显示,基肥翻耕入土后,伴随降雨的产生,长武和梨树点均未产生氨挥发。喇叭口追肥期表施氮肥后,长武和梨树点均产生大量氨挥发(占追施尿素氮量的16%22%),减少追肥用量N 30 kg/hm2(长武点)和N 100 kg/hm2(梨树点)能显著减少氨挥发损失N 8和15 kg/hm2。土壤-春玉米系统氮平衡估算的结果显示,与长武点氮素表观矿化N 97 kg/hm2相比,梨树点仅为N 16 kg/hm2。优化施氮比传统施氮处理显著降低表观氮素盈余N 48 88 kg/hm2。长武点各施氮处理的表观氮素盈余中,约46%的氮素残留在0—1 m的土壤中,54%损失到环境中,氨挥发占总损失的15%30%;梨树点表观氮素盈余中,35%损失到环境中,其中氨挥发占总损失的54%75%,约有65%残留在0—1m的土壤中。梨树点传统施氮处理0—1 m土层的氮素残留达N 140 kg/hm2,部分残留在土壤中的氮素也将面临淋洗、硝化和反硝化等损失的风险。与优化施氮相比传统施氮氮素表观损失增加了约N 30 40 kg/hm2,除氨挥发损失外,淋洗和硝化/反硝化等也是土壤-春玉米系统中不可忽视的氮素损失途径。【结论】我国春玉米主产区农民传统的氮肥用量偏高,增产效应不明显,氮肥损失风险加剧,尤其是氨挥发损失较大,氮肥的优化潜力高达20%33%,相当于可减少施氮N 50 100kg/hm2。

Effect of conventional and optimized nitrogen fertilization on spring maize yield,ammonia volatilization and nitrogen balance in soil-maize system

【Objective】 Two field experiments were conducted in spring maize at Changwu county(CW) of Shaanxi province and Lishu county(LS) of Jinlin province, to compare the effects of optimized and conventional N fertilization on crop yield, NH3 volatilization, and N balance in soil-spring maize system. The objective of the paper was to quantify the N saving potential and NH3 mitigation potential in spring maize under optimization N fertilization. 【Methods】 NH3 volatilization was monitored in situ with a Drger-Tube Method(DTM), which was corrected by a micrometeorological flux method in previous work. Three N treatments: CK(no N application), Ncon(conventional N fertilizer, N 250 kg/hm2 at CW and N 300 kg/hm2 at LS) and Nopt(optimized N fertilization, N 200 kg/hm2), were designed at the two sites. 【Results】 Except CK treatment(7.9 t/hm2 at CW and 3.8 t/hm2 at LS), no significant difference of maize yield between Ncon and Nopt was found at both sites(10.6-10.8 t/hm2 at CW and 9.5-9.6 t/hm2 at LS). In contrast, apparent N recovery was significantly higher in Nopt(44.3%-44.5%) than in Ncon(33.6%-36.4%). Compared with Ncon, apparent N recovery increased by 8.1percentage points and 10.7 percentage points in Nopt at CW and LS, respectively. No obvious NH3 loss was detected during the basal fertilization period with uniformly incorporated fertilizer into soil, combined with later precipitation at both sites. However substantial NH3 volatilization, accounting for 16%-22% of N applied, was found at the two sites during N top-dressing period. Reduced N application of N 30 kg/hm2(CW) and N 100 kg/hm2(LS) could significantly reduce NH3 volatilization(N 8 kg/hm2 at CW and N 15 kg/hm2 at LS). Calculated N balance results showed regional difference for N surplus and apparent N loss between CW and LS sites. For apparent N mineralization, N 97 kg/hm2 was observed at CW site, while only N 16 kg/hm2 at LS site. The Nopt significantly decreased N surplus N 48-88 kg/hm2 compared with Ncon. At CW, about 46% of N surplus was as 0-1 m residual soil N, and 54% of N surplus lost to environment, and NH3 volatilization accounted for 15%-30% of total N loss. At LS, about 65% N surplus existed as 0-1 m residual soil N, 35% of N surplus lost to environment, and NH3 volatilization accounted for 54%-75% of total N loss. Nearly N 140 kg/hm2 of residual soil N in Ncon treatment at LS, while parts of residual soil N may be lost due to N leaching and/or nitrification/denitrification. Compared with Ncon, the Nopt treatment significantly decreased N 30-40 kg/hm2 of N loss. The N loss results also showed large amounts of N unaccounted for(other N loss) was not NH3 loss but a considerable amount of N leaching, and/or denitrification.【Conclusions】 Out results reveal that there is a N saving potential of N 50-100 kg/hm2 or 20%-33% of conventional N rate in major spring maize production area of China without yield loss but significant less N loss to the environment.