不同有机物料还田对华北农田土壤固碳的影响及原因分析

中国农业面临着废弃物数量大、污染严重,农田土壤生产力低的现实问题。该研究以增加农田土壤固碳为目标对砂质农田进行有机物料还田,将秸秆、猪粪、沼渣和生物炭4种物料用尿素调节等氮还田,对农田土壤有机碳、颗粒有机碳、可溶性有机碳和微生物量碳的含量进行测定,并探究不同有机物料还田对土壤有机碳的影响原因。研究结果表明:物料还田3a后,生物炭、猪粪和沼渣处理土壤有机碳(SOC)比秸秆处理分别高262.4%、26.8%和20.7%;2014—2015年生物炭处理的土壤微生物量碳(MBC)较秸秆处理降低2.9%~35.5%,猪粪处理和沼渣处理的土壤可溶性有机碳(DOC)分别提高17.1%~60.1%和7.2%~64.8%;2014—2015年生物炭、猪粪和沼渣处理土壤颗粒有机碳(POC)较秸秆处理提高10.8%~148.2%、9.5%~58.3%和11.3%~57.6%;物料还田后,土壤总有机碳(TOC)和POC呈极显著的回归关系(R2=0.67,P0.001),土壤DOC与MBC有极显著相关性(R2=0.52,P0.001)。与秸秆还田相比,生物炭还田有利于土壤POC的累积进而促进土壤有机碳的提升,猪粪和沼渣则通过提高土壤MBC、DOC和POC的含量,促进土壤有机碳的周转和固定。从农田土壤固碳角度而言,生物炭,猪粪和沼渣还田优于秸秆还田。

Effects and causes of different organic materials amendment on soil organic carbon in North China Plain

A large number of agricultural organic materials unreasonable is disposed becoming the serious problem of environment pollution produced in China each year. The agricultural organic materials amendment is not only mitigates the environment pollution, but also effectively increases soil carbon sequestration. This study conducted in Wuqiao Experiment Station, China Agricultural University in Hebei province, trying mitigating environmental pollution from agriculture and improving soil carbon sequestration in agriculture system while reduces environmental impacts. Four different types of organic wastes were used in this study with pig manure (PM), biogas residue (BR), biochar (BC) and crop straw (ST). The amount of organic materials is applied by the principles that crop residues returning back to the field based on the yields of wheat and maize yields with 7 500 and 9000 kg/hm2, respectively. Besides, the quantity of C added of BC was equivalent to the total amount of C contained in the crop straw of ST treatment. Whereas, the PM and BR was half of ST, considering the C/N of PM and BR, as well as the situation of the organic fertilizer application of field production. As the principle, 4 treatments were applied for the same amount of nitrogen decided by the highest nitrogen treatment (BR). The shortage of nitrogen of PM, BC and ST were is supplied from inorganic fertilizer which applied with the material before wheat sowing. We compared the effect of organic materials on soil organic carbon (SOC), soil particle organic carbon (POC), soil dissolved organic carbon (DOC) and soil microbial biomass carbon (MBC) in three years, and also analysed the reasons of organic materials amendment on soil carbon sequestration. The present study showed that the SOC in BC, PM and BR treatments were higher than that of ST, respectively, with an average value of 262.4%, 26.8% and 20.7% in the third year. Compared to ST, MBC of BC treatment reduced by 2.9%~35.5% in 2014-2015. DOC in PM and BR treatments were 17.1%~60.1% and 7.2%~64.8% higher than ST. Meanwhile, BC, PM and BR treatments increased 10.8%~148.2%, 9.5%~58.3% and 11.3%~57.6% of POC than ST. Furthermore, there was a significant regression between TOC and POC (R2=0.67,P<0.001), Soil DOC was significantly correlative with MBC (R2=0.52,P<0.001). Biochar improve soil POC accumulation, which would enhance the content and stability of soil organic carbon. Pig manure and biogas residue improved soil labile C (e.g. MBC, DOC and POC), which promote SOC transformation and stability in soil. The effect of biocharpig manure and biogas residue amendment was better than straw returning from the perspective of soil carbon sequestration.