Study For Measurement Of Available N In Soil

Nitrogen of the soil is the activity factor in soil fertility and the limit factor in agriculture product. Widespread application of nitrogen fertilizers leads many harmful results, such as low efficiency, low economic return and a serials problem of environmental pollution. Using nitrogen fertilizer equitably according nitrogen-supplying capacity of soil is the core of many problem of improving the efficiency of nitrogen fertilizers; decreasing environmental pollution, enhance the quantity and quality of crop. But the key is studying and choosing the suit testing method and index of nitrogen supplying capacity of soil.In this paper, soils of different layers of different fertility were chosen as experimental soil samples. The soils were tested by aerobic incubation and some chemical methods. The relationships between the testing results and organic matter, total nitrogen, organic nitrogen components were studied. The main results are as follows;1. The mineralizable N of aerobic incubation was very well correlated with the organic matter or total N. But the ratio between the mineralizable N and organic matter or total N was not stable. The minerlizable N was more correlated with the part of easy mineralizable.2. The relationships between the mineralizable N of aerobic incubation and different organic nitrogen components were different. The mineralizable N come mainly from acid-hydrolyable N and was well correlated with the total acid-hydrolysable N, amino acid N, NH+4-N, and amino sugar N, but not with unknown acid-hydrolysable N and non-hydrolysable N. Detail study showed that amino acid N and NH+4-N were two intimate contributors to the mineralizable N, but amino acid N was premier.3. The available nitrogen values determined by different chemical methods were well correlated with the organic matter or total N and more with the part of easy extracted in soil. So there were no differences among different chemical methods and between chemical methods and aerobic incubation in this respect.4. The relationships between available nitrogen values determined by various chemical methods and different organic nitrogen components were different. Some chemical methods'results liked aerobic incubation, and others did not. Amino acid N and NH+4-N were two intimate contributors to available N of most chemical methods, but amino acid N was primary for some methods and NH+4-N for others. For few method, NH+4-N was the only intimate contributors.