Study On The Priming Effect Caused By Ammonium And Mineralization Of Organic Nitrogen In The Typical Soils On Loess Plateau

Typical soil types from north to south in loess plateau were chosen as the objective, the method is Bremner incubation method, the research is focus on the mineralization process of soil organic N and the priming effect of ammonium nitrogen on the organic nitrogen under different environmental conditions on loess plateau. The purpose is to know the factors which influence of N mineralization process and the priming effect of ammonium fertilizer on organic nitrogen of main soil types on loess plateau . So as to give theoretical accordance for further understanding the soil N circle in loess plateau. The results are as follows:1.Using the Bremner method measure the NH4+-N immediately after it was put into the soil, the returning rate was significantly lower than the theoretical value of 100%. Soil type, vegetation type, and organic material have remarkable influence on NH4+-N returning rate (P<0.01). Averagely, the returning rate of Los-Orthic Entisols was highest at 88.8%, Eum-Orthic Anthrosols was lowest at 81.0%. Hap-Ustic Isohumisols and Ust-Sandiic Entisols were in the middle. The returning rate of forest soil, farmland soil, grassland soil, grassland soil and bare-land soil decreased accordingly at 91.0%, 84.6%, 84.0% and 83.7%, the lateral three ones were not significantly different, but they are remarkably lower than the forest soil. The returning rate of reference (CK) soil without intaking organic material was 73.6%, the returning rate of soil with intaking Medicago sativa and Stipa bungeana were 86.7% ad 85.9% respectively, there was no significant difference between the two with organic matter, but they are significantly higher than reference soil, long-term use of N and straw had no significant influence on returning rate (P=0.4365). Correlation Analysis indicated that returning rate is negatively correlated with clay, but significantly positively correlated with organic mater, the sequestration of clay to NH4+-N was the main reason that leads to the decreased returning rate of NH4+-N.2.Non-exchangeable NH4+-N was increasing with increasing the time under Bremner method cultivation. Non-exchangeable NH4+-N increased significant (P=0.0229) of different soil type when cultivated for 20 days, but it was not significant difference when...