Abstract:
To evalate the effects of applying organic fertilizers on the mineralization of carbon and nitrogen in tobacco-growing soil in Chongqing, an indoor, constant-temperature, aerobic incubation method was used. Soil without the application of organic fertilizers served as the control (CK), and treatments involving the application of equal nitrogen amounts of nitrogen in the form of rapeseed cake fertilizer (F), mushroom residue bio-organic fertilizer (B), mushroom residue organic fertilizer (M), and high-carbon base organic fertilizer (H) were set up. The characteristics of soil carbon and nitrogen mineralization were compared between the treatments, and the potential mineralizable organic carbon and turnover rate were estimated using the first-order kinetic equation. The results showed that the rate of soil organic carbon mineralization in all the treatments was faster during the first 30 days of incubation, decreased gradually between 30 and 60 days, and stabilized between 60 and 120 days. At the end of the incubation period, the cumulative mineralization of soil organic carbon in each treatment ranged from 2 667.92 to 2 913.98 mg·kg
-1, with the highest value observed in the F treatment (9.22% higher than CK). The potential mineralizable organic carbon in the organic fertilizer treatments was higher than in CK, with the F treatment showing the highest value of 2.91 g·kg
-1. The carbon mineralization rates of the organic fertilizers were in the order of F > B > H > M. Applying organic fertilizers shortened the turnover period of soil organic carbon and accelerated its turnover rate, with the most obvious effect observed in the F treatment. The application of organic fertilizers increased soil nitrate nitrogen and mineral nitrogen contents, enhancing soil nitrogen mineralization, nitrification rates, and nitrogen mineralization amounts at each incubation stage. Of the four organic fertilizers, the F treatment had the highest rates of soil nitrogen mineralization and nitrification at all incubation stages, while the H treatment had the lowest. Soil carbon and nitrogen mineralization and nitrification rates showed an extremely significant negative correlation with the carbon/nitrogen ratio of the organic fertilizers and an extremely significant positive correlation with the easily decomposable components of the organic fertilizers. Therefore, rapeseed cake fertilizer was suitable for tobacco soil with low nitrogen content, as it could rapidly increase soil nitrogen contents. High-carbon base organic fertilizer, mushroom residue organic fertilizer, and mushroom residue bio-organic fertilizer were recommended for soil with low organic carbon content, as they could enhance soil organic carbon accumulation.