The Comparison Of Several Experiment Methods For Nitrogen Mineralization Of Paddy Soils

The soil nitrogen mineralization has been paid high attention by soil scientists for a long time and obtained lots of achievements already. But, considering the high differences of soils, crops and the ecological conditions, it is still difficult to choose a proper research method for the analysis of nitrogen mineralization for a special soil. Many factors influenced soil mineralization are still ambiguous, for example, how the soil nitrogen mineralization is affected by the continuously waterlogged incubation , or by the water leaching , and how it is affected by the different fertilizer applications. In this study, five paddy soil samples with different fertilities were used for the analysis of soils nitrogen mineralization with several experiment methods, which the methods include waterlogged incubation, waterlogged incubation plus intermittent leaching, KC1 boiling , and the hydrolyzable methods. According the experiment results, several conclusions can be drawn as follows:1 The amount of nitrogen released by mineralization in soil was much difference from the different experiment methods. The amount of nitrogen mineralized in intermittent leaching incubation showed uptrend during the incubation, and it was high than that by continuously waterlogged incubation method. The accumulation of the nitrogen mineralized in the soils would not be higher to increase the leaching frequency. There are no significant relations between the amounts of nitrogen mineralized for five soils in the waterlogged incubation with the total nitrogen amount in the plants.2 The amount of intermittent leaching mineralized nitrogen accumulation is about 1.3 times of that in continuously waterlogged incubation during the 67 days incubation. There were significantly relations for the amount of accumulated nitrogen mineralized between two incubations methods (intermittent leaching and waterlogged incubation), R2=0.8188. It implied that leaching is beneficial to soil mineralization.3 The amount of the nitrogen mineralization by applying nitrogen fertilizer in intermittent leaching incubation is much higher than that of control at about the former 10 day. But after 10 days, the difference becomes not significant. The amount of the nitrogen mineralized by applying nitrogen fertilizer in continuously waterlogged incubation is much higher than that of control during the whole period of incubation. Application of phosphorus fertilizer does not remarkably stimulate the nitrogen mineralization of all soil samples except D soil in the first few days. However, under continuously waterlogged incubation, application of phosphorus fertilizer can boost nitrogen mineralization of all five soil samples.4.The relativity between the nitrogen content of soil by the boiling KC1 method and the totalnitrogen of the plants is significant. The soil nitrogen amount was extreme significant with those by 2MKC1 boiling method, R2=0.9794. And it was close relations between the nitrogen amount pick-upped by KC1 boiling method and the total nitrogen amount in the plants. It can be concluded that the KC1 boiling method is a good method to test nitrogen supply ability by soil.5. The relativity between the soil nitrogen content measured by hydrolyzable method and the total nitrogen in the plants is significant, R2=0.9664. Hydrolysable method is an another good index to test nitrogen supply ability by soil..6 Our experiment results showed that soil clay content and soil pH value were both no significant relations with soil nitrogen mineralization.