不同施肥模式调控沿湖农田无机氮流失的原位研究——以南四湖过水区粮田为例

为探索山东南四湖沿岸麦玉轮作区玉米季内减少土壤无机氮素淋溶和径流损失的施肥策略，降低其对湖区水质产生的潜在威胁，采用田间原位安装淋溶水采集器和地表水径流池收集水样结合室内分析不同形态氮含量的方法，研究了不同施肥模式下无机氮素淋溶和径流损失特征。结果表明：土壤淋溶水量及地表水径流量与降水呈显著正相关关系，其水量受秸秆类物质还田的影响；硝态氮(NO3--N)与铵态氮(NH4 -N)随地表水径流损失的浓度及总量均明显高于淋溶水，由径流方式损失的氮素占2/3以上，是氮素以水溶液形式流失的主要途径；淋溶和径流均以NO3--N损失为主(径流损失中NO3--N占总量的82.9%-90.8%，淋溶损失中NO3--N占63.5%-72.9%)，地表径流水NO3--N浓度对水质有较大影响，但土壤淋溶水NO3--N浓度对地下水污染不构成威胁；农民习惯施肥处理在玉米整个生育期淋溶和径流氮损失最高。在保证玉米产量前提下，降低氮素流失造成湖区的污染，平衡施用氮磷钾肥、施用控释氮肥、有机替代无机和秸秆还田等措施均可在沿南四湖区农田使用。

In situ study on influences of different fertilization patterns on inorganic nitrogen losses through leaching and runoff: a case of field in Nansi Lake Basin

Nansi Lake is the largest lake in Shandong province and the northern area of China, which is an important buffer lake of the South-to-North Water Diversion Project (east route). Eutrophication has become the central problem of water environment in Nansi Lake where the eutrophic state is from mesotrophic state to hypereutrophic state. A field study was conducted to investigate the characteristics of inorganic N loss by leaching and runoff during the maize growing season in the Nansi Lake Basin, and determine fertilizer application strategies to reduce N losses and their potential threats to lake water quality. Under different fertilization patterns (In this experiment, 7 different fertilization treatments were installed, such as follows: (1) CK: no fertilizer was applied to soil; (2) FP: farmer's practice of traditional fertilization; (3) PK: in this treatment, only phosphate and potash fertilizer applied to soil; (4) OPT: nitrogen, phosphate and potash fertilizers were mixed to a balanced nutrition; (5) CRF: in the treatment, controlled-release nitrogen fertilizer replaced common nitrogen fertilizer, and other nutrition was invariable; (6) 80%OPT+M: total amount of nutrition applied to soil was equal to the 4th treatment, but 20% of total inorganic nutrition was replaced by that existed in the organic matter-poultry excrement; (7) OPT+St: a balanced N, P and K nutrition was applied to soil, and total amount was equal to the 4th treatment, meanwhile, wheat straw was returned to cover the soil surface), Collectors for leaching and surface runoff water were installed in-situ in each treatment. Water samples were collected for analysis of different forms of inorganic nitrogen in laboratory. The results indicated a positive correlation between quantity of leachate water, surface runoff water and precipitation. The amount of water was affected by substances such as wheat straw; The Concentration and total amount of NO^-₃-N and NH⁺₄-N losses from runoff were significantly higher than their losses through leaching, and accounts for 2/3 or more of N losses, which was the primary means of N losses in the form of aqueous solutions. N losses through leaching and runoff were mainly NO^-₃-N form (NO^-₃-N runoff loss accounted for 82.9%-90.8% of total, and leachate water loss accounted for 63.5%-72.9% of total N. Concentration of NO^-₃-N in runoff water greatly affected water quality, but it did not constitute a threat to groundwater pollution through leaching; N losses through leaching and runoff were highest in treatment FP (Farmers practice) for the whole maize growing season. To maintain maize grain yield while reducing N pollution of the lake, a balanced application of NPK fertilizer is required, combined with the application of controlled-release nitrogen fertilizer, organic alternative to inorganic and the use of straw incorporated into the soil. Appropriate practices will need to be introduced to the farmland in the Nansi Lake basin.