[Effects of Straw Addition on NO and CO Emissions from Red Soil Subjected to Different Long-Term Fertilization].

Straw return, as an important measure for soil fertility improvement in farmland, significantly affects the emissions of greenhouse gases NO and CO. Thus, the collected soil samples from five long-term (30-year) fertilization treatments (no fertilization, CK; recommended chemical fertilizer, F; 200 % of recommended chemical fertilizer, 2F; pig manure, M; and chemical fertilizer combined with pig manure, FM) were amended with and without straw and incubated under constant temperature and humidity conditions (25 ℃ and 65 % maximum field water holding capacity) for 20 days so as to investigate the key factors influencing NO and CO emissions in response to straw addition in long-term fertilization treatments. The results showed that fertilization significantly increased NO emissions. Compared to those under the unfertilized treatment[(22.05 ±2.09) μg·kg, calculated as nitrogen, the same as below], cumulative NO emissions from the chemical fertilizer treatments significantly increased by 119 %-195 %[(48.38 ±20.81) μg·kg and (65.13 ±12.55) μg·kg from the F and 2F treatments, respectively], and those from the manure treatments increased by 275 %-399 %[(82.72 ±12.73) μg·kg and (1 101.99 ±425.71) μg·kg from the M and FM treatments, respectively]. Soil NO-N, DOC, and DTN were the main factors influencing NO emissions from fertilized treatments in the absence of straw addition. Straw addition significantly increased cumulative NO emissions by 345 % and 247 % in the 2F and M treatments, respectively, compared to those in the corresponding fertilized treatments without straw addition, with no significant effect on NO emissions in the CK, F, and FM treatments. Straw addition increased DOC content and microbial activity and decreased soil NO-N and DTN contents, thereby increasing NO emissions. Fertilization also significantly increased CO emissions. Compared to those from the unfertilized treatment, cumulative CO emissions from the manure treatments significantly increased by 120 %-130 %[(122.11 ±4.3) mg·kg (calculated as carbon, the same as below) and (116.47 ±4.55) mg·kg from the M and FM treatments, respectively], and those in the 2F treatment increased by 28 %[(65.13 ±12.55) mg·kg]. In the absence of straw addition, soil MBC, DOC, and DTN were the main factors influencing CO emissions. Compared to those in the treatments without straw addition, straw addition significantly increased cumulative CO emissions by 660 %-1132 % among fertilization treatments, due to increased DOC and MBC contents and enhanced microbial activity. In conclusion, straw addition significantly increased NO and CO emissions through increased soil DTN consumption and DOC content among fertilization treatments. In soils treated with manure amendment, straw return should be rationally considered for the purpose of balancing the comprehensive trade-offs between fertility improvement and greenhouse gas emissions.