油菜秸秆生物质炭对紫色土有机碳矿化和累积效应的影响

Effects of Rape Straw Biochar on Organic Carbon Mineralization and Accumulation in Purple Soil

采用室内模拟培养试验,以油菜秸秆为对比,分析油菜秸秆生物质炭的施用对紫色土有机碳矿化的影响。在培养试验中,设置0.25%,0.5%和1%3个不同秸秆/土壤质量比的油菜秸秆还田培养处理,依次标记为J_1,J_2和J_3;同时,设置3个不同油菜秸秆生物质炭添加量的培养处理,其生物质炭添加量分别为J_1,J_2和J_3处理中添加的等量油菜秸秆在600℃下制成的生物质炭量,依次标记为S_1,S_2和S_3,所有处理置于25℃下避光培养56d。在培养期内,各处理中土壤有机碳(SOC)矿化速率随时间的变化符合乘幂函数。添加生物质炭处理的SOC累积矿化量、矿化强度和易分解有机碳占总有机碳含量的比例(Ca/CSOC)显著低于与其对应的油菜秸秆处理(P<0.05),表明油菜秸秆经过热解制成生物质炭后可显著提高其在土壤中的稳定性。各添加生物质炭处理的SOC累积矿化量、矿化强度、Ca/CSOC和难分解有机碳占总有机碳含量的比例(Cs/CSOC)与对照(无外源碳添加)之间无显著性差异,添加生物质炭几乎不影响紫色土有机碳的分解。另外,S_1处理中外源碳的表观残留率显著高于其它培养处理,而S_2和S_3处理中外源碳的表观残留率则显著低于与其对应的油菜秸秆处理(J_2和J_3)(P<0.05)。这表明在低量油菜秸秆还田时,将其制成生物质炭还田比直接还田更利于紫色土有机碳的积累。

An incubation experiment was conducted in the laboratory to investigate the effects of rape straw biochar and rape straw on soil organic carbon（S_OC）mineralization of purple soil.The experimental soil and rape straw were sampled from Dianjiang county,Chongqing city.In this experiment,different amounts of rape straw（straw/soil mass ratio is 0.25%,0.5% and 1%）were added to soils in J_1,J_2 and J_3treatments,respectively.We also established 3treatments with the addition of different amounts of biochar,which were made by the same amount of rape straw in J_1,J_2 and J_3treatments under 600℃,respectively,and marked as S_1,S_2,and S_3 treatments in turn.All the treatments were incubated for 56 dunder 25 ℃.In the whole incubation period（56d）,the temporal changes of mineralization rate of soil organic carbon followed a power function.The cumulative mineralization amount and mineralization intensity of soil organic carbon,and the ratio of degradable organic carbon content to total organic carbon content（Ca/CSOC）in soil in the biochar treatments were significantly lower than those in the corresponding rape straw treatment（P〈0.05）.The results indicated that after the rape straw was made into biochar through pyrolysis,the stability of rape straw biochar in the soil was significantly higher than that of rape straw.There was no significant difference in the cumulative mineralization amount and mineralization intensity of soil organic carbon,Ca/CSOCand the ratio ofdifficultly decomposed organic carbon content to total organic carbon content between the biochar treatment and control treatment（no exogenous carbon added）,which suggested that the addition of biochar did not affect the SOC decomposition of purple soil.In addition,the apparent retention rate of the exogenous carbon was significantly higher in the S_1 treatment than in other incubation treatments,while the apparent retention rates of the exogenous carbon in the S_2 and S_3 treatments were significantly lower than those in the corresponding rape straw treatments（J_2and J_3）,respectively.The results indicated that the biochar return was more beneficial to organic carbon sequestration in purple soil than the direct rape straw return when the amount of rape straw returned to field was at a low level.