内蒙古河套灌区主要作物农田氮素平衡及潜在污染状况分析

为从氮素平衡的角度研究河套灌区氮素潜在污染风险，本文以河套灌区主要种植作物玉米和向日葵为研究对象，分析了传统种植模式下玉米和向日葵收获期农田土壤无机氮残留现状，并从氮素平衡角度利用氮素盈余、氮素潜在损失对玉米和向日葵种植的环境污染风险进行了分析。结果表明：河套灌区农田土壤残留无机氮随着施氮量的增加而增加，玉米田和向日葵田0~90 cm土壤无机氮（以N计）平均残留量分别为66.11 kg·hm^-2和45.53 kg·hm^-2。灌区中部的五原县玉米田土壤无机氮残留量最高，可达336.93 kg·hm^-2，向日葵田以东部乌拉特前旗最高，残留量达273.66 kg·hm^-2。玉米田和向日葵田平均氮素年输入总量分别为514.81 kg·hm^-2和314.73 kg·hm^-2，以化肥氮为主，占总氮素输入的85%以上。氮素输出主要是作物吸收带走，玉米和向日葵平均氮素年输出总量为362.10 kg·hm^-2和209.65 kg·hm^-2。过高的氮素输入导致玉米和向日葵年平均氮素盈余分别高达235.71 kg·hm^-2和168.08 kg·hm^-2，并伴随着每年169.60 kg·hm^-2和122.55 kg·hm^-2潜在损失的氮素。通过氮素平衡的综合分析得出，内蒙古河套灌区保持现有产量水平的玉米氮肥推荐用量约为280 kg·hm^-2，向日葵为150 kg·hm^-2，与目前河套灌区玉米和向日葵氮肥投入相比，分别节约198 kg·hm^-2和128 kg·hm^-2，同时该施用量也可以显著降低潜在损失的氮，降低环境压力。

Analysis of nitrogen balance and potential pollution of main crops in the Hetao Irrigation area of Inner Mongolia

The potential nitrogen pollution risk in the Hetao Irrigation area was studied from the perspective of nitrogen balance to provide a scientific basis for farmland nitrogen management in this area. Soil nitrogen balance is an important parameter to evaluate nitrogen use efficiency and environmental risk in farmlands. In this paper, maize and sunflower were selected as the main crops in the Hetao Irrigation area. The status of soil inorganic nitrogen residues during harvest under the traditional planting mode was investigated. The environmental pollution risk in maize and sunflower fields was analyzed through the potential loss of surplus nitrogen from the perspective of nitrogen balance. The residual inorganic nitrogen in a farmland in the Hetao Irrigation area increased with increasing nitrogen application rate. The average residual inorganic nitrogen at a depth of 0~90 cm in maize and sunflower fields was 66.11 kg·hm^-2 and 45.53 kg·hm^-2, respectively. The maize field, located in the central Wuyuan County, had a residual inorganic nitrogen amount of 336.93 kg·hm^-2, while the sunflower fields located in the east of Ulate south Banner, had the highest residual amount of 273.66 kg·hm^-2. The annual input of nitrogen in maize and sunflower fields was 514.81 kg·hm^-2 and 314.73 kg·hm^-2, respectively. Fertilizer nitrogen was the main nitrogen input, accounting for more than 85% of total nitrogen input. Nitrogen output was mainly absorbed and assimilated by crops. The average annual nitrogen output of maize and sunflower fields were 362.10 kg·hm^-2 and 209.65 kg·hm^-2, respectively. The annual nitrogen surplus values of 235.71 kg·hm^-2 and 168.08 kg·hm^-2, respectively, were accompanied by a substantial amount of potential nitrogen loss 169.60 kg·hm^-2 and 122.55 kg·hm^-2, respectively. According to the comprehensive analysis of nitrogen balance, the recommended nitrogen fertilizer amount for maize and sunflower to maintain the current yield level in Hetao irrigation area of Inner Mongolia is about 280 kg·hm^-2 and 150 kg·hm^-2, respectively. Compared with the current nitrogen fertilizer input of maize and sunflower in Hetao irrigation area, this fertilizer application rate can save 198 kg·hm^-2 and 128 kg·hm^-2, respectively.This also can significantly reduce the potential loss of nitrogen and reduce environmental pressure.