生物质炭与秸秆配施对紫色土团聚体中有机碳含量的影响

Effect of Combined Application of Biochar and Straw on Organic Carbon Content in Purple Soil Aggregates

以油菜/玉米轮作农田生态系统为研究对象,通过田间微区试验,研究了生物质炭、秸秆(BC:8000 kg·hm^-2生物质炭、CS:8 000 kg·hm^-2秸秆、0.5BC:4 000 kg·hm^-2生物质炭、0.5CS:4000kg·hm^-2秸秆、BC+CS:4 000 kg·hm^-2生物质炭+4 000 kg·hm^-2秸秆)与化肥配施对紫色土团聚体含量及稳定性、土壤有机碳及有机碳在各粒级团聚体中分布的影响,为合理利用有机物料及为紫色土培肥提供依据。结果表明:(1)与对照(CK)相比,秸秆、生物质炭还田(除0.5BC处理外)均能提高>2 mm粒级团聚体含量,降低<0.053 mm粒级团聚体含量,同时提高水稳性团聚体的平均重量直径(MWD)、几何平均直径(GMD)、大于0.25 mm团聚体含量(R(0.25)),其中只有CS处理达到了显著水平,且随着秸秆施用量增加,效果越显著。CS+BC处理则能显著提高0.25~2mm粒级水稳性团聚体含量。(2)除CS处理,其他各处理较CK均能显著提高土壤总有机碳含量,其中BC和CS+BC处理分别提高了45.55%和44.45%(P<0.05),效果优于单施秸秆处理,且随着生物质炭施用量的增加,土壤总有机碳呈增加趋势。对不同粒级团聚体有机碳而言,各处理的团聚体有机碳主要分布在<0.053mm和>2mm粒级团聚体中;BC处理较其他处理能提高土壤不同粒级团聚体有机碳含量,其次为CS+BC处理。(3)通过计算团聚体有机碳贡献率发现,各处理对土壤团聚体有机碳贡献率主要分布在0.25~2 mm和<0.053 mm粒级团聚体中,其中仅CS处理显著提高了>2 mm粒级团聚体有机碳贡献率,较CK提高了53.53%;CS+BC、0.5BC处理分别较CK显著提高了<0.053 mm粒级团聚体有机碳贡献率,增幅为26.20%,48.63%。(4)秸秆和生物质炭还田能提高玉米和油菜的生物产量和经济产量,其中CS、BC、CS+BC效果较明显。总之,秸秆与生物质炭配施是改善紫色土结构和提升碳水平的较优培肥措施。

【Objective】Purple soil is weak in erosion resistance,and its soil aggregates are also vulnerable in structure.This study was oriented to explore how to reasonably utilize organic material resources,like crop straw,and improve structure of the purple soil,and how organic carbon is distributed in soil aggregates of the purple soil in the Sichuan Basin.【Method】A tract of farmland under the rape/maize rotation ecosystem was selected for an in-situ filed experiment to explore effects of application of chemical fertilizer coupled with biochar and/or crop straw on content and stability of soil aggregates and soil organic carbon of the purple soil and distribution of organic carbon in aggregates by fraction.The experiment was designed to have control(CK)and 5 treatments,that is,CK(application of chemical fertilizer only),BC(application of chemical fertilizer+8 000 kg·hm^-2 biochar),CS(application of chemical fertilizer+8 000 kg·hm^-2 straw),0.5BC(application of chemical fertilizer+4 000 kg·hm^-2 biochar),0.5CS(application of chemical fertilizer+4 000 kg·hm^-2 straw)and BC+CS(application of chemical fertilizer+4 000 kg·hm^-2 biochar and 4 000 kg·hm^-2 straw).【Result】Results show:(1)compared with the control(CK),all the treatments,except for Treatment 0.5BC,increased the content of>2 mm aggregates,while reducing the content of<0.053 mm aggregates.They also increased mean weight diameter(MWD)and geometric mean diameter(GMD)of the water-stable soil aggregates and content of the>0.25 mm aggregates(R0.25),with Treatment CS,in particular,where the effects became more significant with rising straw application rate.Treatment CS+BC significantly increased the content of 0.25~2 mm water-stable aggregates.(2)Except for Treatment CS,all the treatments significantly increased the content of total soil organic carbon as compared with CK.Among them,Treatment BC and CS+BC treatment did by 45.55%and by 44.45%,respectively(P<0.05),and the effect of Treatment CS was not so significant.With rising biochar application rate,the content of total organic carbon in the soil increased correspondingly.The increase was especially significant in<0.053 mm and>2 mm fractions of soil aggregates;Compared with other treatments,Treatment BC increased the content of organic carbon in all soil aggregates in the soil,regardless of size fraction,and followed by Treatment CS+BC in this effect.(3)By calculating contribution rate of each fraction of aggregates to total organic carbon in the soil,it was found out that the effects of the treatments increasing contribution of soil aggregates to total organic carbon in the soil were the most significantly reflected in the 0.25~2 mm and<0.053 mm fractions of soil aggregates.However,Treatment CS was the only one that significantly increased the organic carbon contribution rate of the>2 mm fraction of soil aggregates,or by 53.53%as compared with CK,and Treatment CS+BC and 0.5BC increased the rate of the<0.053 mm fraction of aggregates by 26.20%and 48.63%,respectively.(4)Application of straw and/or biochar increased the biomass and economic yield of maize and rapeseed,especially Treatments CS,BC,and CS+BC in the experiment.【Conclusion】Combined application of straw and/or biochar with chemical fertilizer is an effective practice to improve structure of and increase carbon content in the purple soil.