Abstract:Soil nitrogen (N) mineralization is a critical ecological process of N cycling that plays an important role in determining soil N-supplying capacity. Based on a long-term fertilization experiment on paddy field in the Dongting Lake region, China, the responses of organic N mineralization in 0~20cm soil layer and associated temperature sensitivity to different fertilization were studied. The experiment included five treatments: CK (without fertilization), CF (farmers’ practice of applying chemical fertilizer NPK), NK (application of chemical fertilizer NK), NPK (balanced application of chemical fertilizer NPK), HOM (combined application of chemical fertilizer NPK and organic fertilizer). All sampled soils were waterlogged incubated for 42d at different temperatures (5℃, 15℃, 25℃ and 35℃), and accumulated mineralized N was analyzed. Compared with CK treatment, the accumulated mineralized N produced during 42d incubation increased significantly (P<0.05) under different fertilization treatments while the increases gradually decreased from 32.7%~80.4% to 14.9%~59.7% along with the increment of temperature. The relationship between cumulative mineralization and effective accumulated temperature well fitted the effective accumulated temperature model (EATM) in all treatments at 25℃ and 30℃, and the values of K and n associated parameters in EATM in all fertilization treatments were higher by 2.7% ~ 39.5% and 4.0% ~21.3% than those in CK treatments, respectively, suggesting long-term fertilization presented obvious increased effects on both soil N supplying intensity at initial stage and later N mineralization rate. Moreover, the potentially mineralizable N (No) and mineralizable ratio of soil N were significantly (P<0.05) increased by 22.4% ~72.4% and 7.8% ~ 39.0%, respectively, when fertilization was adopted, and the HOM treatment presented the best results. The values of temperature sensitive coefficient (Q10) of soil N mineralization rate constant was ranged from 1.77 to 2.09 within the temperature range of 5 ~ 35℃;the values of Q10 and activation energy (Ea) for soil N mineralization were significantly (P<0.05) lower in all fertilization treatments than those of no fertilizer treatment, which followed the descending order of CK, CF, NK, NPK and HOM. The Q10 value for each treatment was higher from 5℃ to 15℃ than that from 15℃ to 25℃ and from 25℃ to 35℃, indicating that the most sensitive scope for response of N mineralization to soil temperature was at 5 ~ 15℃. It can be concluded that HOM treatment presented better effects in improving soil N mineralization capacity, optimizing N mineralization process and decreasing associated temperature sensitivity as compared with any other chemical fertilizer treatment, suggesting combined application of chemical N, P, K and organic fertilizer should be proposed for the rice production in the studied area.
