Nitrogen mineralization in paddy soils of the Taihu Region of China under anaerobic conditions: dynamics and model fitting

Abstract

The processes and characteristics of nitrogen mineralization in paddy soils of the Taihu Region of China were studied with 120-day anaerobic incubation at 25 and 35 °C. Results showed that the organic nitrogen mineralized ranged from 4.0% to 9.4% of total N (60–241 mg kg −1) and that the mineral N was only correlated with total N (partial correlation analysis). The pH changed greatly and was related to the mineral nitrogen contents during mineralization. Temperature was one of the main factors influencing the mineralization of nitrogen. Four models, (1) effective cumulated temperature model; (2) a one-component, first-order exponential model (one-pool model); (3) a two-component, first-order exponential model (two-pool model); and (4) a two-component, mixed first- and zero-order exponential model including a constant term (special model), were fitted to the observed mineral N vs. incubation days using a non-linear regression procedure. The exponential models were significantly better than the effective cumulated temperature model, and the two-pool model and the special model gave the best fits among the four models. The special model was the unique one that could appropriately reflect the responses of organic nitrogen mineralization to incubation temperature in all studied paddy soils. All results showed that the special model made a better prediction of nitrogen mineralization under flooded conditions than the other models.