Soil Available Nitrogens As Affected By Added Nitrogens, Litter Falls And Its Secondary Metabolites

Soil available nitrogens were investigated by 84-day lab incubations after adding inorganic nitrogens, leaf litters and litters secondary metabolites into soils as red soil, yellow red soil, yellow soil, meadow soil collected from Wuyi Mountain at different altitudes. The results showed that, the contents of nitrate nitrogen in red soil and yellow meadow soil were significantly reduced by adding ammonium nitrogen. The contents of ammonium nitrogen in red soil and yellow soil were far larger than the added ammonium amount, and the content of ammonium in yellow meadow soil were all long increased in the incubation time at HN, which means that the ammonification after addition of ammonium nitrogen was intensified. Nitrate applied to soil can inhibit soil nitrification, compared with the control, the increase rates of nitrate content in red soil and mountain meadow soil were declining with the incubation time, but kept nearly constant for the yellow meadow soil. Ammonium contents for yellow meadow soil and mountain meadow soil increased significantly after addition of nitrate, but changed insignificantly for the red soil. It means that nitrogen can promote nitrate nitrogen transforming into ammonium nitrogen, or losing of gas form, and different soils have different result.The nitrate and ammonium nitrogen contents for yellow soil was significantly reduced by adding broadleaved litter, but unchanged for the mountain meadow soil and the decrease rate for coniferous litter treatment is lower than that for broad litter. The effect of bamboo litter on the yellow soil is small, but the significant decrease of nitrate and ammonium nitrogen content of red soil was found. The nitrate and ammonium nitrogen content for all soils decreased significantly by adding polyphenol material, the decrease rates of nitrate nitrogen were lower than those of ammonium nitrogen. The content of soil soluble nitrogen reduced may be related with ammonium nitrogen, but does not rule out the influence of soluble organic nitrogen. The soil microbial biomass nitrogen was inhibited by adding a high level of polyphenol material in red soil, yellow red soil, yellow meadow soil, but a low level of polyphenol material added would promote microbial biomass N. These results indicated that the effects of added nitrogen, litter, and polyphenol material would be changed with different soil physical and chemical properties and nutrient status. Litter, phenolic compounds influence the efficiency nitrogen in soil under the Simulation nitrogen deposition conditions shows:under the ammonium nitrogen conditions, increase the litter and tannic acid could not improve soil nitrification; increased needle litter significantly reduce soil ammonium nitrogen; under the nitrate nitrogen conditions, there have more losses of soil nitrate nitrogen in soil, but the content of ammonium nitrogen did not increase, this could not explain by the nitrogen transformation. The soil nitrogen content did not increase when adding more litter, it maybe related with the litter chemical composition and the influence of microorganisms. Nitrogen has certain influence to tannins and litter reducing the efficiency nitrogen in soil, it should be more research.