【目的】探讨长期施肥下黑土重金属的演变特征,为该地区科学施肥和土壤环境保护提供理论依据。【方法】设计长期定位施肥试验:CK(对照,不施肥)、N(氮)、NP(氮磷)、NPK(氮磷钾)、NPKM(氮磷钾+有机肥)和1.5NPKM(1.5倍的NPKM),共6个处理。试验采集起始(1989年)和各施肥年限(1994、2000、2006、2010、2012年)的耕层(0—20 cm)土壤样品,测定Cu、Zn、Pb、Cd总量和有效态含量,并计算其活化度。【结果】长期施用化肥不影响黑土重金属总量、有效态含量。Pb不受施肥影响,Cu、Zn、Cd受粪肥影响,其总量和有效态都显著增加,Cu和Zn活化度增加,但Cd活化度显著降低(维持在8%—9%,明显低于化肥处理的35%)。长期施用有机肥,重金属演变呈现阶段性。1989—2000年缓慢增加,2000—2010年快速增加,2010年后稳定或缓慢下降。1.5NPKM 3个阶段Cd总量变化分别为0.03 mg·kg-1·a-1、0.07 mg·kg-1·a-1、-0.13 mg·kg-1·a-1;NPKM处理的Cu有效态变化分别为0.11 mg·kg-1·a-1、0.53 mg·kg-1·a-1、-1.25 mg·kg-1·a-1。重金属演变的阶段性是源于粪肥重金属含量的阶段性变化,即养殖方式的变化。金属活化度相关性分析表明:Cu与Olsen-P、Zn与SOM皆显著正相关,而Pb与pH显著负相关;Cd与Olsen-P和SOM显著负相关,与pH显著正相关,意味着Cd对土壤性质的响应更加复杂。【结论】长期施用化肥对重金属演变没有明显影响,长期施用有机肥显著改变了其演变特征,重金属演变呈现出先缓慢增加、然后快速增加、最后稳定或缓慢下降的阶段性变化,而且阶段性演变特征源于粪肥金属含量的阶段性变化。在农业生产中,既要适度增施有机肥又要关注其潜在风险,现有施肥量(30 t·hm-2)和玉米种植体系下,当地牛粪长期施用仍存在很大风险。
【Objective】 It is necessary to assess the evolution of heavy metals in soils under long-term fertilization and cropping, which helps rational fertilization and healthy soils in the area.【Method】At a long-term Black Soil experimental station, Jilin, China, six treatments were selected in this study, including CK(control without fertilization), N(nitrogen), NP(nitrogen + phosphorus), NPK(nitrogen + phosphorus + potassium), NPKM(nitrogen + phosphorus + potassium + manure), and 1.5NPKM(1.5 times of NPKM). The soil in a 0-20 cm layer in each plot for each treatment was sampled in 1989, 1994, 2000, 2006, 2010, and 2012, respectively, and the total/available metal content(Cu, Zn, Pb, and Cd) was measured. Additionally, the metal activity index was also calculated. 【Result】 The results showed that the total and available metals(Cu, Zn, Pb, and Cd) did not change with the fertilization year in CK and those treatments receiving chemical fertilizers; except Pb significantly increased under manure application(NPKM and 1.5NPKM). However, Cd activity index decreased markedly by 27%-28% for manure treatments. Three stages in the evolution of soil metals with long-term manure application, attributed to the stage-by-stage change in the metal content of animal manure, were presented, that is, there was a slow increase between 1989 and 2000, a rapid increase between 2000 and 2010, and it kept steady or slowly decreased after 2010. For example, 0.03 mg·kg-1·a-1, 0.07 mg·kg-1·a-1, and-0.13 mg·kg-1·a-1, respectively, for total soil Cd in 1.5NPKM, and 0.11 mg·kg-1·a-1, 0.53 mg·kg-1·a-1, and-1.25 mg·kg-1·a-1, respectively, for available soil Cu in NPKM, were assessed in the three stages above mentioned. Further, a partial correlation analysis showed that the activity index of Cu, Zn, and Pb was positively related to Olsen-P, SOM, and negatively related to soil pH, respectively; whereas the Cd activity index was negatively related to Olsen-P and SOM and positively re