Effects Of Long-term Fertilization On Soil Organic Nitrogen Fractions And It's Profile Distribution

Based on long-term rotation of wheat and maize, the objective of the research was to study the effect of long-term chemical N fertilization or the mixture of chemical N fertilizer and other manures on irrigated desert soil organic nitrogen components. By soil organic nitrogen classification method proposed by Bremner in 1965, this paper studied the forms and compositions of Organic nitrogen (N) on irrigated desert soil in the oasis area of Zhangye after 25 years located experiment. In order to compare the effects of long-term different fertilization on organic N fractions, content and soil profile distribution. It has important practical significance to improve the utilizing efficiency of N on irrigated desert soil in the oasis area of Zhangye.This study set-up eight treatments: no fertilizer treatment(CK), nitrogen fertilizer(N), nitrogen and phosphate fertilizer(NP), nitrogen and phosphate and potassium fertilizer(NPK), organic and nitrogen fertilizer (MN), organic fertilizer and nitrogen and phosphate fertilizer(MNP), organic with nitrogen and phosphate and potassium fertilizer(MNPK). The rotation sequence was wheat followed by field pea.Results showed as follows:1. Soil total nitrogen and organic nitrogen fractions were significantly influenced by long-term application of chemical fertilizer and manure and varied with fertilizer species. Compared with application of N and P fertilizes, manure with N fertilizes greatly increased the contents of total N, acid hydrolysable N and nonhydrolysable N; Of the forms of acid hydrolysable N, amino acid N and hydrolysable unidentified N were significantly increased and amino sugar N is increased also by manure with N and P fertilizers. Similar to manure with chemical fertilizer, N application significantly increased total N, acid hydrolysable N and nonhydrolysable N. Compared to the plots without N addition, N fertilizer significantly increased ammonium N but little affects amino acid nitrogen; amino sugar N and hydrolysable unidentified N. P and K fertilizer application did not significantly affect total N and organic N forms in irrigated desert soil.2. Long-term application of fertilizers can improve soil organic nitrogen in cultivated layer (0~20cm), especially, the application of animal manure and chemical fertilizers in combination significantly increase the soil organic nitrogen content. Extent of increasing content of organic nitrogen, animal manure and chemical fertilizers in combination is higher than that of chemical fertilizer treatment or animal manure3. From 2003 to 2006, after three years of continuous testing, the handling area which the chemical fertilizer and organic fertilizer were applied significantly increased the contents of total soil nitrogen, acid hydrolysable N and nonhydrolysable N. Of the forms of acid hydrolysable N, The treatment of single-organic fertilizer mainly increased the contents of hydrolysable unidentified N, the treatment which single-chemical fertilizer applied significantly increased the content of ammonia nitrogen, the plots of organic manure and chemical fertilizers combined greatly increased content of ammonium N and hydrolysable unidentified N. The increasing of amino acid N, N-sugar content in all the treatment area was not obvious.4. Soil total nitrogen and organic nitrogen fractions in soil profile were significantly influenced by long-term application of chemical fertilizer and manure and varied with fertilizer species. the content of total N and organic N forms were decreased with layers depth, but the ration of organic N forms to total N didn't had obvious rule. The difference of organic nitrogen forms was mainly in 0~100cm soil layer under different fertilizer species, Organic nitrogen forms was small differences in 100~180cm soil layer, but below 180cm soil layer the difference was no obvious. At various soil layers, acidic hydrolysable N was the main components of the organic N. Compared with application of N and P fertilizes, manure with N fertilizes greatly increased the contents of total N and acid hydrolysable N in 0~100cm soil layer. Of the forms of acid hydrolysable N, amino acid N and hydrolysable unidentified N were significantly increased. Amino sugar N is increased also by manure with N and P fertilizers in 0~40cm soil layer. At all the soil layer of 0~200cm, N application significantly increased total N, acid hydrolysable N and nonhydrolysable N. Compared to the plots without N addition, N fertilizer significantly increased ammonium N but little affects amino acid nitrogen; amino sugar N and hydrolysable unidentified N.