State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences
Supported by the National Key Research and Development Program of China (No. 2017YFD0200200/08) and the National Natural Science Foundation of China (No. 31872957)
集约化菜地因高量施肥以及大水漫灌导致其在农田磷污染排放中的占比最高，目前已成为种植业磷损失的优先阻控对象。在定量评估菜地周年磷损失量的基础上，明确蔬菜合理的磷肥投入阈值范围，通过源头控制菜地磷的迁移、流失，对于有效降低中国农业面源污染造成的环境压力具有重要意义。以太湖流域露天菜地为研究对象，设置农民习惯施磷（对照）和减量施磷处理（减施20%、30%、50%和100%），通过为期一年的蔬菜轮作试验，明确土壤磷素环境阈值及磷素周年径流流失特征。结果表明，菜地磷环境阈值为78.9 mg?kg-1，所有处理土壤表层有效磷（Olsen-P）含量均超过环境阈值。随施磷量的减少，菜地总磷（TP）径流损失浓度降低，并主要以可溶性磷（DP）流失形态为主，DP/TP比例为50.1%～63.1%。磷径流损失负荷呈现出明显的季节性特征，夏秋季磷素流失量为1.93～3.26 kg?hm-2（以P计），占全年磷素流失通量的59.2%～63.2%。结构方程模型结果表明，当季施磷量直接且极显著影响TP流失浓度，并且TP流失浓度对TP流失负荷存在极显著的正向影响，影响系数为0.97。菜地施肥处理的磷肥流失系数在1.36%～3.33%，减磷50%的流失系数最低。与对照相比，随施磷量的减少，磷径流损失削减效果越好，减磷100%的削减率达41.5%。三季蔬菜种植中，减磷20%和减磷30%处理的蔬菜产量和对照无显著差异，减磷20%处理出现增产趋势。综合考虑环境风险和经济产量，推荐露天菜地减施20%～30%的磷肥比较适宜。
【Objective】Intensive vegetable fields have been the priority control projects for phosphorus (P) loss in farming due to massive fertilization and flood irrigation, accounting for the highest proportion of P pollution from farmlands. Therefore, (i) quantifying the assessment of the annual P loss of vegetable fields, (ii) clarifying the reasonable threshold range of phosphate fertilization for vegetables, and (iii) controlling P migration and loss from vegetable fields through the source are of great significance for effectively reducing the environmental pressure caused by agricultural non-point source pollution. 【Method】A plot experiment in the Tai Lake Basin with conventional fertilization and phosphate fertilization reduction treatments was conducted in a perennial and open vegetable field. The one-year vegetable rotation experiments focused on clarifying the environmental threshold of P and annual P runoff loss characteristics. There were five treatments, conventional fertilization (CK), reduction of 20% (P-20), 30% (P-30), 50% (P-50), and 100% (P-100) based on conventional P fertilization. 【Result】 The environmental threshold of soil P in the tested vegetable fields was 78.9 mg?kg-1. During the whole experimental period, Olsen-P content in the soil surface of different treatments exceeded the leaching threshold. The results of annual total P (TP) runoff loss concentration in vegetable fields showed that with the decrease of phosphate fertilization input, the annual loss concentration of TP decreased. Also, dissolved P (DP) was the dominant form of P species, accounting for 50.1%～63.1%. Runoff loss loads of P showed seasonal characteristics, with the amount of P loss in a summer-autumn season (1.93～3.26 kg?hm-2), accounting for 59.2%～63.2% of the annual P loss flux. Based on the structural equation modeling (SEM), the amount of phosphate fertilizer had a direct and extremely significant effect on TP loss concentration. Furthermore, TP loss concentration had a positive and extremely significant impact on TP runoff loss load with a path coefficient of 0.97. The loss coefficients of P were between 1.36% and 3.33%, and the lowest loss coefficient was in the P-50 treatment. With a decreased amount of P applied, the reduction ratio of P runoff loss increased, and a P loss reduction rate of 41.5% was recorded in the P-100 treatment. Treatments of P-20 and P-30 had no significant yield reduction during a three-successive vegetable growth period in a year compared with CK. 【Conclusion】 Taking environmental risk and economic yield into consideration, it is appropriate to reduce between 20%～30% P fertilizer application based on conventional phosphate fertilizer rate for open vegetable fields in Tai Lake region.
WANG Rui, SHI Weiming, LI Yilin. Evaluation of Phosphate Fertilizer Reduction on Annual Phosphorus Loss under Intensive Open-field Vegetable Production[J]. Acta Pedologica Sinica, DOI:10.11766/trxb202102050078,[In Press]