秸秆及其生物炭对土壤碳库管理指数及有机碳矿化的影响

以河南省粮食主产区壤质潮土和砂土为研究对象,通过盆栽试验和室内恒温培养试验,研究了生物炭与不同腐殖化程度的传统有机物料(秸秆和腐熟鸡粪)单施及配施对壤质潮土和砂土有机碳储量、活性及碳库管理指数的影响,并进一步比较了小麦秸秆直接还田和制炭还田对土壤有机碳矿化的影响,以及生物炭对土壤原有有机碳矿化的调控作用。结果表明:相同添加量下,生物炭对土壤有机碳含量的提升效果优于秸秆和腐熟鸡粪,在壤质潮土和砂土上分别较对照提升了63.15%和115.62%。另外,生物炭显著增加了土壤稳态碳含量和土壤碳库指数(CPI),但降低了土壤碳素有效率(SC)和碳库活度指数(AI),对土壤易氧化有机碳(POXC)和碳库管理指数(CMPI)无显著影响,添加秸秆显著增加了2种土壤POXC含量、基础呼吸和CPMI。进一步通过室内恒温培养试验发现,秸秆可在培养前期(0～37天)大幅度提升2种类型土壤有机碳矿化速率和累积矿化量,秸秆制炭还田对土壤有机碳矿化无显著影响。此外生物炭对土壤原有有机碳矿化的调控作用受其施用量、外源活性有机碳输入和土壤类型的影响,高量生物炭(2%)对非秸秆还田土壤有机碳矿化表现出较强的负激发效应,而低量生物炭(0.55%)对秸秆还田土壤有机碳矿化表现出较明显的负激发效应。因此,从"固碳减排"角度考虑,秸秆制炭还田是更合理的利用方式,且应根据土壤施肥管理措施和土壤类型考虑生物炭的施用量,添加质量比为2%的生物炭可显著抑制土壤原有有机碳矿化,降低CO_2排放,但应避开秸秆快速腐解期施用。

Effects of Straw and Biochar on Soil Carbon Pool Management Index and Organic Carbon Mineralization

Pot experiment and indoor thermostatic incubation experiment was conducted to study the effects of single and combined application of biochar and traditional organic materials (wheat straw and chicken manure) on organic carbon storage, activity and carbon pool management index of loamy fluvo-aquic soil and sandy soil in Henan Province, meanwhile, the effect of wheat straw returning and carbon-making returning on soil organic carbon mineralization and the regulation of biochar on soil original organic carbon mineralization were compared furtherly. The results showed that under the same application amount, the biochar and organic materials could increase soil organic carbon (TOC), and the highest TOC content was found in the soil treated by biochar, the content of TOC were increased by 63.15% and 115.62% in loamy fluvo-aquic and sandy soil, respectively. Moreover, biochar significantly increased soil stable organic carbon content and carbon pool index (CPI), while decreased soil carbon activity index (AI) and the effectiveness of carbon (SC), but had no significant effect on the content of potassium permanganate oxidizable carbon (POXC) and carbon pool management index (CPMI), and adding straw significantly increased POXC content, basic respiration and CPMI of two kinds of soils. Through indoor soil incubation experiment, the SOC mineralization rate and cumulative mineralization amount of the two types of soils were increased by straw at the early stage of cultivation (0~37 days), but there was little impact on SOC mineralization if the straw was made into biochar and added to the soil. The priming effects of biochar on soil native SOC mineralization were restricted by its application amount, exogenous active organic carbon input and soil type. In the soil without straw returning, high biochar (2%) showed stronger negative priming effect on soil organic carbon mineralization, while low biochar (0.55%) showed more apparent negative priming effect soil organic carbon mineralization in the straw returning field. Therefore, from the perspective of carbon sequestration and emission reduction, compared with the direct returning straw to field, returning the straw prepared into biochar was a more reasonable way of utilization, and the application amount of biochar should be considered according to soil fertilization management measures and soil types. Application biochar with a mass ratio of 2% could significantly inhibit the mineralization of soil native organic carbon and reduce CO₂ emissions, but it should not be applied during the rapid decomposition period of straw.