秸秆生物质炭对土壤结构体与活性碳分布、转化酶动力学参数及小麦生长的影响

为探明生物质炭输入土壤后与水稳性团聚体的作用机理,及对土壤活性碳库、微生物活性、作物生长的促进作用。以生物质炭和秸秆碳为外源碳材料,两者等碳量添加条件下,在小麦不同生育期采用湿筛法、电镜扫描、酶动力学方程等方法,测定土壤结构、酶活性、活性有机碳、及小麦产量等指标的响应情况。结果表明:生物质炭添加下,土壤0.25 mm大颗粒团聚体显著增加了16.9%—45.8%;土壤结构体分布以土壤大颗粒团聚体为主,含量约为小颗粒团聚体的2倍。生物质炭少量或适量添加(0.8%或2.4%),土壤微生物量碳增加了9.7%—33.6%,溶解性有机碳降低了12.6%—27.5%;而过量添加下(8%),则呈现正好相反的规律。生物质炭输入下,转化酶动力学参数Km、Vmax、k分别下降了17.3%、17.0%、16.1%。生物质炭适量添加下,小麦产量增加了14.9%—19.1%;秸秆3%和10%添加水平下,小麦产量则下降了37.3%和90.1%。整体而言,生物质炭通过增加0.25 mm大颗粒团聚体的形成及土壤转化酶的活性来促进土壤结构和作物的生长的改善,且生物质炭在2.4%水平下的生物质炭添加改善作用最为突出,有助于研究区域过剩秸秆资源的资源化利用。

Effects of biochar application on the distribution of soil aggregates and active organic carbon, kinetic parameters of soil invertase, and wheat growth

This study was conducted to evaluate the effects of biochar (BC) application on the active organic carbon and microbial activity in the soil, and crop growth, as well as the action mechanism between biochar and water-stable aggregates (WSA) in the soil. Biochar and straw were added at 1%, 3%, and 10% in straw treatments (Str_1.0, Str_3.0, and Str_10.0, respectively) and 0.8%, 2.4%, and 8% in biochar treatments (BC_0.8, BC_2.4, and BC_8.0, respectively). With biochar and straw applied at equal C rates, the wet sieving method, scanning electron microscope, and kinetic model equation were used to investigate the responses of enzymatic activity, soil structure, active organic carbon, and wheat yield. The results indicated that the proportion of macro-aggregates (> 0.25 mm) was significantly increased by 16.9%-45.8% in biochar treatments, while the proportion of macro-aggregates was double that of micro-aggregates in the treatment where straw was applied in excess. Soil microbial biomass C content was increased by 9.7%-33.6%. However, the dissolved organic C content was decreased by 12.6%-27.5% in BC_0.8 and BC_2.4, while the reverse was observed in BC_8.0. The kinetic parameters of the enzyme (michaelis constant, maximum enzyme velocity, and velocity constant) were decreased by 17.3%, 17.0%, and 16.1% in biochar treatments, respectively. Compared with the control, wheat yields were increased by 14.9%-19.1% in BC_0.8 and BC_2.4, while it decreased by 37.3% and 90.1% in Str₃ and Str₁₀, respectively. In general, soil structure and wheat growth were promoted by increasing the formation of soil WSA fractions that were >0.25 mm and invertase activity. Biochar applied at the rate of 2.4% was beneficial for improving the soil structure and crop growth, and is effective for the utilization of excess plant residues in the study area.