长期施用有机物料对稻田生态系统服务功能的影响

Effects of long-term application of organic materials on the ecosystem services of paddy fields

基于长期定位试验,测定稻田温室气体排放通量、土壤和糙米重金属、淋溶水中氮磷含量,收集整理水稻产量和土壤肥力长期数据,以研究长期施用有机物料对稻田生态系统服务功能的影响。选择净经济效益(NEB)作为生态系统服务功能的评价指标。研究结果表明:与单施化肥(F)相比,长期施用猪粪(FM)显著提高土壤有机碳、全氮、全磷和有效磷含量,秸秆还田(FS)显著提高土壤有机碳和速效钾,提高了全氮、全磷、速效氮和全钾,但差异不显著,说明长期施用有机物料可提高土壤肥力;FM和FS提高水稻平均产量分别达4.1%和4.3%;FS和FM显著增加CH_4累积排放量,减少N_2O排放,但差异不显著;FM和FS提高土壤有机碳固存率。与F和FS相比,FM降低了淋溶水中氮淋溶量,但显著增加了田面水磷含量和20 cm深淋溶水磷淋溶量,而对60 cm和80 cm深淋溶水磷淋溶量没有影响;FM显著提高土壤Zn、Cu和Cd含量,所有处理重金属含量均没有超过土壤环境质量二级标准,FM没有引起水稻糙米中重金属含量的累积。与F相比,FM增加NEB 5.2%,达到1 056.8元·hm^(-2)。上述结果表明,20年尺度下,施用猪粪对稻田生态系统服务功能的正面影响远大于其所带来的负面影响,但随着猪粪施用时间的延长其负面效应可能进一步扩大,应引起重视。

There are many individual studies on the effects of long-term application of organic materials on ecosystem services of paddy fields in terms of grain yield, greenhouse gas emissions, heavy metals, and nitrogen and phosphorus leaching, but few have comprehensively monitored or assessed the effects with a comprehensive index. We examined greenhouse gas emissions, heavy metal accumulation in soil, nitrogen and phosphorus leaching, rice yield, and soil fertility data from a 20-year（1997—2016）experiment to explore the effects of three different treatments, namely chemical fertilizer application（F）, pig manure plus chemical fertilizer application（FM）and straw plus chemical fertilizer application（FS）, on the ecosystem services of paddy fields. The net economic benefit（NEB）was chosen as a key index for evaluating ecosystem services. Compared to F, FM significantly（P〈0.05）increased the contents of soil organic carbon（SOC）, total N, total P, and available P. FS significantly（P〈0.05）increased the contents of SOC and available K. In addition, FS and FM consistently increased rice yield by 4%. FS and FM increased CH4 emission and annual SOC sequestration rate and decreased N2O emission. Moreover, compared to F and FS, FM decreased the N load in percolating water and significantly increased the P concentration in surface water and P load in perco-lating water at 20 cm depth, while water at 60 cm and 80 cm was not affected. FM also significantly（P〈0.05） increased the contents of zinc, copper, and cadmium in soil, but all of the heavy metals did not exceed the Soil Environmental Quality Standard Ⅱ. FM did not cause the accumulation of heavy metals in brown rice, indicating that the contents of the heavy metals in brown rice were within safe limits. Compared to F, FM increased the NEB by about 5.2%（1 056.8 yuan·hm-2）. Taken together, our results suggest that the positive effects of pig manure on ecosystem services of paddy fields outnumbered its negative effects at a timescale of 20 years.