Effects Of Nitrogen Fertilization On Soil Nitrogen Leaching Loss And Carbon Emission In Rubber Forest Soil

Reasonable application of nitrogen is an important measure ensure high and stable yield of Hevea Barasiliensis.High temperature,high humidity and heavy rainful are typical prharacters of tropical monsoon climate and this kind climate may cause the loss of nitrate leaching.Making clear of nitrogen loss way,carbon emission quality and soil respiration changing after nitrogen fertilization in rubber plantation ecosystem are benefit for nitrogen management and control,carbon and nitrogen pool cultivation,soil fertility improvement.Therefore,field experiment is conducted to research carbon emission rate and flux,cabon accumulation movement,leaching and soil respiration under 4 nitrogen level(Non nitrogen,NO;Low nitrogen,100 kg N ha^-1,Neon;In the nitrogen,230 kg N ha^-1,with organic fertilizer 30 kg N ha^-1,Nbal;high nitrogen,400 kg N ha^-1,N400).Results are as follows:（1）After the urea was applied to acidic laterite,the hydrolysis was completed in a very short time.Several days after fertilization,the content of NH4-N and pH reached the peak,and then with the nitrification in soil,ammonium nitrogrn content decreased rapidly and become stabilized after several days.Under field conditions,the nitrification process in acid red soil is affected by nitrogen application rate,soil pH,soil temperature and soil temperature.And there was a significant positive correlation between net nitrification rate and nitrogen application rate（r=0.724*,P<0.05）.（2）In dry season,the nitrate nitrogen accumulated in 0-100 cm and lower concentration of nitrate nitrogen was leaching in soil profile,but after heavily rain,a high concentration was leaching.When fertilizer on soil surface,the nitrogen rate in four different level was about 1.77-35.52 kg N ha^-1,and N400 leaching rate was 8.44%,which was significant higher than other treatments.（3）Nitrogen was leached in different amount after fertilize nitrogen,about 0.26-0.88 kg N ha^-1,and N400 is significantly higher than other treatments;different nitrate nitrogen flux between 0.11-3.73 kg N ha^-1 and total amount of nitrogen leaching 0.15-4.61 kg N ha^-1,N400>Nbal>Ncon=NO.under arid climate condition,the nitrogen leaching rate was low and may the flux rate of nitrogen leaching was underestimated by leakage meter method.（4）The carbon emission rate of soil espiration changed with season in rubber forest and showed a multi-peak curve in one yeari.Compared with non-nitrogen treatment,lower nitrogen levels different affect soil respiration significantly,but when nitrogen was fertilized successively,soil respiration and carbon emission was promoted significantly.compared withN400 and Ncon,Nbal fertilizers with organic manure did not cause a significant loss in soil carbon emission.