碳氮添加对雨养农田土壤全氮、有机碳及其组分的影响

为探明碳氮添加4年后,土壤全氮、有机碳及其组分(可溶性有机碳、微生物量碳、轻组和重组有机碳)的变化特征,依托布设于甘肃省定西市安定区李家堡镇的不同碳源配施氮素田间定位试验,涉及秸秆、生物质炭、氮素3个因素,秸秆设置为不施、施用秸秆2水平;生物质炭为不施和施用生物质炭2个水平;氮素设置为不施氮、施纯氮50 kg/hm^2、施纯氮100 kg/hm^2 3个水平,共9个处理。结果表明:不同处理下土壤全氮、有机碳及其组分的含量均随土层的加深而降低。添加生物质炭对土壤全氮、有机碳及其组分均具有不同程度的提升效应。添加秸秆对土壤全氮、有机碳和可溶性有机碳、微生物量碳、轻组有机碳均具有显著提升效应,仅在0-5 cm土层对重组有机碳有显著提高。添加氮素可显著提升土壤全氮、有机碳和可溶性有机碳、微生物量碳、轻组有机碳含量。较其他处理,添加生物质炭对土壤全氮、有机碳和重组有机碳的提升效应最高,添加秸秆对可溶性有机碳、微生物量碳、轻组有机碳的提升效果最优。从提升土壤质量的角度出发,推荐秸秆配施氮素模式,该模式下土壤碳素有效性高、易于被微生物利用,有利于作物生长。从提高土壤固碳角度考虑,推荐生物质炭配施氮素模式,该模式有利于碳的封存。

Effects of Carbon and Nitrogen Addition on Total Nitrogen, Organic Carbon and Their Components in Rain-fed Farmland

In order to find out the change characteristics of soil total nitrogen (TN), organic carbon (SOC) and its components (dissolved organic carbon (DOC), microbial biomass carbon (MBC), light fraction organic carbon (LFOC) and heavy fraction organic carbon (HFOC)) after four years of carbon and nitrogen addition, local field experiment of nitrogen application with different carbon sources was conducted at the Rainfed Agricultural Experimental Station of Gansu Agricultural University in Lijiabao Town, Anding District, Dingxi City, central Gansu Province. Three factors including straw, biochar and nitrogen were set up in the experiment. The straw was set at two levels, including no straw and straw application, and the experiment involved two biochar levels, which were no biochar and biochar application, and the nitrogen application was at three levels of no application, 50 kg/hm² and 100 kg/hm², totally nine treatments. The results showed that the contents of TN, organic carbon and their components decreased with the deepening of soil layer under different treatments. Application of biochar increased the concentrations of SOC, TN, DOC, MBC, LFOC and HFOC. Application of straw significantly increased the contents of SOC, TN, DOC, MBC and LFOC, but only significantly increased HFOC content in 0-5 cm soil layer. Application of nitrogen significantly increased the concentrations of SOC, TN, DOC, MBC and LFOC. Among the treatments, application of biochar showed the best improve effect on the concentrations of SOC, TN and HFOC, and adding straw represented the best enhancement effects on the concentrations of DOC, MBC and LFOC. From the perspective of improving soil quality, straw combined with nitrogen was the recommended application mode, which had a higher soil carbon availability that facilitated the carbon utilization of the microorganisms, and benefited the growth of crops. Considering the improvement of soil carbon sequestration, biochar combined with nitrogen was the recommended application mode, which was beneficial to the carbon sequestration.