减量施氮与间作大豆对华南地区甜玉米农田氮平衡的影响

本文在广东广州华南农业大学试验中心,通过大田定位试验(2015—2016年两年4季)对比了两种施氮水平减量施氮(300 kg·hm~(-2),N1)和常规施氮(360 kg·hm~(-2),N2)]、3种种植模式甜玉米单作(SS)、甜玉米//大豆2∶3间作(S2B3)、甜玉米//大豆2∶4间作(S2B4)]农田生态系统的氮素输入、输出和平衡状况,旨在为减少化学氮肥投入水平,提高氮素利用效率,在华南地区发展环境友好型的玉米可持续生产模式提供科学依据。结果表明:1)减量施氮与甜玉米//大豆间作降低了系统氮素总输入量,大豆固氮和秸秆还田降低了化肥氮输入的比重,与常规施氮相比,减量施氮下SS、S2B3和S2B4的化肥氮输入占年均氮素总输入的比例分别下降3.24%、3.64%和3.77%。2)间作大豆增加了系统籽粒氮素累积量,N1和N2处理甜玉米//大豆间作的年均籽粒氮素累积量分别是单作甜玉米的2.43倍和2.18倍;减量施氮与甜玉米//大豆间作能降低甜玉米农田氮素损失,N1和N2处理甜玉米//大豆间作的年均氨挥发量分别比单作甜玉米低39.02%和27.26%;间作甜玉米的氮淋溶量比单作低13.85%。3)减量施氮与间作大豆显著降低了系统氮素盈余量,S2B3-N1、S2B3-N2和S2B4-N1、S2B4-N2年均氮素盈余量分别为71.03 kg·hm~(-2)、133.7 kg·hm~(-2)和42.87 kg·hm~(-2)、100.64 kg·hm~(-2),分别比SS处理N1和N2的平均值减少81.27%、64.75%和88.69%、73.47%。因此,减量施氮甜玉米//大豆间作模式能维持系统作物产量、减少生产成本、降低环境污染风险,具有较高的经济和生态效益。

Effect of nitrogen reduction and soybean intercropping on nitrogen balance in sweet maize fields in South China

The increasing demand for fresh sweet maize (Zea mays L. saccharata) in South China has led to the prioritization of finding solutions to environmental pollution caused by continuous production of the crop and high inputs of chemical nitrogen fertilizer. A promising method for improving crop production and environmental conditions is to intercrop sweet maize with legumes. Here, a field experiment was conducted at Experimental Center of South China Agriculture University for two years (2015-2016) to investigate nitrogen input, output and balance in sweet maize farmlands in South China under two nitrogen levels reduced nitrogen dose of 300 kg·hm^-2 (N1) and conventional nitrogen dose of 360 kg·hm^-2 (N2)] and three cropping patterns sole sweet maize (SS), sweet maize//soybean intercropping with sweet maize to soybean line ratios of 2:3 (S2B3) and 2:4 (S2B4)]. The purpose of the study was to provide scientific basis for reducing chemical nitrogen fertilizer input, improving nitrogen use efficiency and developing a sustainable sweet corn production model in South China. Results showed that:1) reduced nitrogen application and sweet maize//soybean intercropping decreased total nitrogen input and the proportion of chemical nitrogen input through soybean nitrogen fixation and straw return. Nitrogen fertilizer input under SS, S2B3 and S2B4 accounted respectively for 84.29%, 55.42% and 59.06% of total annual nitrogen input under N1 and for 87.53%, 49.93% and 53.70% under N2. 2) Accumulated nitrogen amount of grain under intercropping system was significantly higher than that under sole sweet maize. Average annual grain nitrogen accumulation of sweet maize//soybean intercropping was 2.18-2.43 times of that of SS. Sweet maize//soybean intercropping reduced ammonia volatilization significantly and thereby reduced the risk of nitrogen leaching. Compared with SS, S2B3 and S2B4 reduced annual ammonia volatilization and nitrogen leaching under N1 by 35.97% and 14.74%, 42.07% and 11.54%, respectively. Treatment S2B4-N1 had the lowest ammonia volatilization, which was 38.72 kg·hm^-2. Meanwhile, annual ammonia volatilization and average annual nitrogen leaching in S2B3 and S2B4 under N2 reduced respectively by 24.55% and 12.89%, 29.98% and 16.23% than that under N1 treatment. 3) Annual nitrogen surpluses under S2B3-N1, S2B3-N2, S2B4-N1 and S2B4-N2 were respectively 71.03 kg·hm^-2, 133.7 kg·hm^-2, 42.87 kg·hm^-2 and 100.64 kg·hm^-2, which were 81.27%, 64.75%, 88.69% and 73.47% lower than the average of SS under N1 and N2. Overall, the study demonstrated that intercropping combined with reduced-nitrogen rate maintained sweet maize production, reduced production cost, while also reducing environmental impact. Intercropping with soybean and reduced nitrogen application may be a more sustainable and environmentally friendly way for production of sweet maize in South China.