Dynamics Of Soil Nitrogen Mineralization At Four Different Land Use Types In A Coastal Areas In Northern Jiangsu Of China

Soil Nitrogen (N) mineralization rate is often used to be as the index of soil N availabilityand its losses. The effect of different land use on soil N mineralization, transportation,absorption and utilization of plant may lead to difference of soil nitrogen cycle. We selectedfour different land use patterns (i.e. poplar plantation, crop-poplar integrated system, meadowand cropland) in a coastal area of northern Jiangsu as the experimental sites. The variations ofsoil mineral N were determined by Close-Top incubation method. The soil net N mineralizationrate, soil microbial biomass nitrogen (SMBN), water-soluble nitrogen (WSON) and soil physicaland chemical properties were analyzed. The results are showed below:(1) The results showed that the net N mineralization rate was decreased in turn of poplarplantation, crop-poplar integrated system, cropland and meadow. The amount of net Nmineralization rate changed very consistent in different seasons. Seasonal dynamics of net Nmineralization rate under four land use types were significant. The concentration of net Nmineralization rate in spring was higher than those in autumn, winter and summer, generally.(2) The soil mineral nitrogen decreased with increasing soil depth.(3) The contents of ammonium N were higher than those of nitrate N under different landuses. Ammonium N accounted for50.26%. Seasonal dynamics of ammonium N and nitrate Nunder four land use types were significant. The concentration of ammonium N and nitrate N inspring was higher than other three seasons, generally.(4) The soil ammonium N had significant correlation with total mineralization nitrogen, butthere were no significant correlation between nitrate N and total mineralization nitrogen. Thereexisted significant correlations between ammonium N and microbial biomass nitrogen, totalnitrogen, net N mineralization rate, C/N; there were significant positive correlations betweennitrate N and microbial biomass nitrogen, water-soluble nitrogen, organic carbon, respectively.(5) In25~40cm soil layers, the soil mineral nitrogen had significant difference betweenpoplar plantation and crop-poplar integrated system. In poplar plantation and meadow, the soilmineral nitrogen had significant difference between25~40cm and0~10cm,10~25cm soil layers.To account the four land uses, the seasons and the depths, the concentration of soil mineralnitrogen was significantly higher in poplar plantation than those in cropland and meadows in0~10cm depths. Seasonal dynamics of soil mineral nitrogen under four land use types weresignificant. The concentration of soil mineral nitrogen in spring was higher than those in winterunder poplar plantation and crop-poplar. Under cropland and meadow the seasonal changeswere relatively slight.