Effects Of Long-term Fertilization On Organic Nitrogen Form And Content In Black Soil

Organic nitrogen is the main form of the soil nitrogen and it is an important hub station inthe nitrogen cycle. So to study organic nitrogen content of each component and morphology oflong-term changes in the sustainable use of farmland ecosystems are important.This researchwas studied on the basis of a long-term experiment in black soil, available nitrogen, totalnitrogen and nitrogen content of different particles in continuous fertilization were analyzed bytesting soil samples. At the same time, the content and form of organic nitrogen weredetermined by using the method of Bremner, the effect of long-term fertilization on the organicnitrogen functional group of the bulk soil and its clay particle was studied by soft X-rayabsorption nitrogen K-edge structure in Synchrotron radiation. The results showed that:1. Alkali-hydrolysable nitrogen of surface soil in various fertilizer treatments is obviouslyhigher than that of the subsurface soil. Alkali-hydrolysable nitrogen of arable layer soil for CKtreatment in2008decreased9.4%comparing to leisure treatment; and chemical fertilizer ofeach treatment had no obvious change, chemical and manure mix fertilizer significantlyincreased. Alkali-hydrolysable nitrogen content of surface soil in2012for CK treatment andchemical fertilizer treatments reduced in different degree than that in2008; but that ofsubsurface soil had opposite conclusion.2. Change regular of total nitrogen of soils in2012and in2008was similar. Total nitrogenof surface soil and subsurface soil of1.5M1NPK treatment was the highest in each treatment,which were2.37g/kg and2.65g/kg respectively. The effect of NPKS treatment on surface soilwas bigger than that on subsurface soil, chemical and manure mix fertilizer could significantlyincrease total nitrogen; in the same condition, total nitrogen of surface soil and subsurface soil in2008were lower than that in2012. In surface soil and subsurface soil in2008, total nitrogencontent for CK treatment and chemical fertilizer treatments were lower than that of leisuretreatment, that for NPKS treatment and for leisure treatment were flat.3. Long-term fertilization has significant effect on organic nitrogen component.55.6%-78.3%of nitrogen in black soil was acid-hydrolyzable nitrogen,21.7%-54.46%of totalnitrogen in soils was acid insoluble nitrogen; chemical and manure mix fertilization couldincrease component of organic nitrogen; amino acid nitrogen content for long-term manure andstraw application treatments obviously increased, straw could restrain acid hydrolysis ofammonia nitrogen.CK treatment comparing to leisure treatment amino sugar nitrogen decreased in2008, and other components of the organic nitrogen content decreased;acid hydrolysis of totalnitrogen content and rate for chemical fertilizer treatment and NPKS treatment in2008werehigher than that in2012; the content and rate of amino sugar nitrogen of PK treatment increasedobviously.4. Sand, silt and clay is most sensitive to the nitrogen of organic fertilizer. The nitrogencontent which combine to clay is apparently higher than sand and silt in different fertilizationtreatments. NPKS and chemical and manure mix fertilization have the important influence onsand. Nitrogen content of NPKS treatment was40.86%, which was higher than that of CK,treatment with chemical and manure mix fertilization is2.0~2.3times of CK treatment.5. After long-term fertilization in all treatments, the relative proportions of amide/amine inbulk soil and clay particle were the highest, which were the most major forms of soil organicnitrogen functional group; compared to the Fallow treatment, the relative proportions ofamide/amine of CK treatment were lower, and proportion of Pyrrole N was higher; for chemicaland manure fertilization treatment, the proportion of amide/amine decreased with the increasingof manure application rates, but the Pyrrole N had the opposite trend. The proportion ofamide/amine of NPKS treatments was the highest in bulk soil; and the relative proportion ofnitrile N/aromatic N of Fallow treatment in clay particle was the highest..