栖霞市苹果园氮磷养分平衡及环境风险评价

栖霞市是中国最主要的苹果产区之一,近年来果园单位面积养分的大量投入造成了区域氮、磷元素的过量富集,进而对当地的土壤、水资源、大气等环境要素造成一定的污染。因此,了解苹果主产区施肥现状,并科学评价其环境风险具有重要的现实意义。以栖霞市为研究区域,通过实地调研、田间试验、室内模拟等方法,分析了苹果园氮磷养分的输入量及输出量,进而构建养分平衡模型,对区域环境风险进行了综合评价。研究结果表明:1)2018年栖霞市苹果园养分投入量为:有机质5360.28 kg/hm^2,N 545 kg/hm^2,P2O5568.76 kg/hm^2,K2O 712.57 kg/hm^2;2)氮素的气态损失、果实及枝条带走量各占输入总量的6.49%、24.34%、3.12%,盈余率达66.04%(402.97 kg/hm^2);磷素被果实和枝条带走量分别占输入总量的12.33%和2.55%,盈余率达85.12%(484.75 kg/hm^2);栖霞市氮、磷盈余量均超出环境安全的阈值,分别属于中风险和高风险范围。因此,在保证果园产量与品质的前提下,适当减少化肥使用量、逐步建立水肥一体化的果园施肥模式、提升果农科学的管理经验,应成为果园可持续发展的主攻方向。

Nitrogen and phosphorus nutrient balance and environmental risk assessment of apple orchard in Qixia city

Abstract: Qixia city is one of the most important apple producing areas in China. In recent years, a large amount of per unit area nutrient input of orchards had resulted in excessive enrichment of nitrogen and phosphorus in the region, which had further polluted the local soil, water resources, atmosphere and other environmental elements. Therefore, it was of great practical significance to clarify the current situation of fertilization in main producing areas of apple and scientifically evaluate the environmental risks. Taking Qixia city as the research area, from May to July 2018, the basic situation, fertilization pattern and fertilization quantity of apple orchards in this area were obtained through field investigation and questionnaire survey. From August to November 2018, a field experiment was conducted in a typical apple orchard to obtain nitrogen gas loss data of base fertilizer in apple orchard. From December 2018 to March 2019, nitrogen gas loss data of apple orchards were obtained by laboratory simulation. Based on quantifying the input and output of nitrogen and phosphorus nutrients in apple orchards, the surplus nitrogen and phosphorus nutrients of apple orchards in Qixia city was calculated by constructing a nutrient balance model. Finally, by dividing the environmental risk grade of nitrogen and phosphorus surplus in apple orchards, the regional environmental risk of Qixia city was evaluated comprehensively. The results showed that: 1) In 2018, nutrient input of apple orchards in Qixia city was as follows: organic matter 5 360.28 kg/hm2, N 545 kg/hm2, P2O5 568.76 kg/hm2, K2O 712.57 kg/hm2. Among them, N, P2O5 and K2O input through base fertilizer accounted for 82.23%, 81.82% and 70.41% of the total. Only 17.77%, 18.18% and 29.59% were absorbed through top dressing; 2) Gaseous loss of nitrogen, fruit and branch carry away accounted for 6.49%, 24.34% and 3.12% of the total input, respectively, with a surplus rate of 66.04% (402.97 kg/hm2). The phosphorus taken away by fruits and branches accounted for 12.33% and 2.55% of the total input, respectively, with a surplus rate of 85.12% (484.75 kg/hm2). The surplus amounts of nitrogen and phosphorus in Qixia city both exceed the threshold of environmental safety, which belong to the range of medium risk and high risk respectively. In conclusion, excessive application of nitrogen and phosphorus fertilizers will inevitably pose a threat to the soil, land surface and groundwater resources and atmospheric environment of Qixia city. Therefore, on the premise of ensuring the output and quality of orchards, it should be the main direction of sustainable development of orchards to appropriately reduce the use of chemical fertilizer, gradually establish an integrated fertilization model of water and fertilizer, and improve the management experience of fruit farmers.