Effect Of Different Crop Residues And Soil Properties On CO₂-C Evolved Rate And PH In Red Soil

Global change and soil acidification are great environmental issues at the current stage in the world. Therefore, it's very important and urgent to investigate the decomposition dynamic of the crop residuse and its impact on soil pH in agricultural soils. In the present paper, we collected the soil samples with different fertilizer treatments( CK, NPK, NPKM, M) from a 19-year long-term field experiment to examine the effect of different crop residues addition (wheat, rape and Chinese milk vetch) and soil properties on CO₂-C evolved rate and pH in soils under laoaratory incubation conditions.Crop residues addition rapidly increased CO₂-C evolved rate in soil. At the initial 7-day decomposition stage, CO₂-C evolved rate in soil with manure treatment was higher than that without manure treatment. At the later decomposition stage, CO₂-C evolved rate was not significantly different among different fertilizer treatments. Cumulative CO₂-C evolved over 105 days from soils with manure treatment was higher than that with manure treatment.CO₂-C evolved rate was negatively correlated with the C/N ratio of crop residues, positively with N concentration of crop residues and initial total N concentration in soil and soil organic matter at the earlier decomposition stage. CO₂-C evolved rate was negatively correlated with N concentration of crop residues, positively with C/N ratio in crop residues and soil organic matter at the later decomposition stage. N in crop residues and soils played the most important role on residues decomposition in the initial 7-day incubation, but effect of soil organic matter and initial soil pH increased at the later decomposition stage.In the whole incubation time, soil pH initially increased, and then decreased following the addition of crop residues. However, during the whole incubation period crop residues addition caused a significant increase in soil pH. Higher soil pH was found in Chinese milk vetch treatment than in wheat and rape treatments at the initial incubation period. At the later incubation period, Soil pH decreased more quickly in Chinese milk vetch treatment than in wheat and rape treatments exception the soil with NPK fertilization treatment. The response of soil pH change to the addition of crop residues depended on the crop residues types and initial soil pH. Soil pH change among different crop residues was closely related to total N concentration or N/C ratio) in crop residues.