The Effects Of Biochar On Nitrogen Utilization And Maize Growth On Brown Soil

In recent years, the amount of nitrogen fertilizer application was employed to enhance crop yield. But a low nitrogen utilization rate maintain still a low level. Many nitrogen was lost by ammonia volatilization, leaching and N2O emissions. The results were not only the fertilizer resources which were wasted, but also caused severe soil acidification, eutrophication, agricultural non-point source pollution of the environment. The sustainable developments of agriculture were restricted by the problems. Many researches indicated that biochar is important to enhance nitrogen utilization rate. Therefore, it is significant to clarify the regularity of the maize nitrogen absorption and the distribution of the nitrogen.To study the effects of biochar on Maize nitrogen utilization, a 15N isotope tracer pot experiments were carried out in order to monitor Ammonia volatilization, Nitrous Oxide emissions, nitrogen leaching, dynamic distribution of inorganic nitrogen and fertilizer 15N the fate, when soil was treated by biochar for two years during 2012-2013. During 2013, a field trial from Shenyang Agricultural University was settled from brown soil of long-term fertilization experiment station to study effects on dynamic growth, dry matter, maize yield and maize grain quality, when soil was treated by different amount of biochar. The pot experiment included three biochar-treated:(1) CK (without fertilizer and biochar), (2) N (conventional fertilizer application without biochar-treated), (3) NB (conventional fertilizer application with biochar-treated, and its dosage was 1.64% of the soil per pot, equivalent to field dose of 40 thm-2). The 15N abundance of the urea which used in pot experiment was 10%. Five treatments were arranged in field trial:(1) B0 (without fertilizer and biochar-treated), (2) B20 (without fertilizer, but the biochar was applied at rate of 20 t·hm-2), (3) NB0 (conventional fertilizer application without biochar-treated), (4) NB20(conventional fertilizer application with biochar-treated at rate of 20 t·hm-2), (5) NB40 (conventional fertilizer application with biochar-treated at rate of 40 t·hm-2). Ammonia volatilization was tested by semi-closed acid absorption method. The flux of N2O was measured by a closed chamber-gas chromatography method, soil available nitrogen content was determined by continuous flow analysis method, the N content in plant and soil was analysed using elemental analyzer, the content of the total nitrogen in the leaching solution was determined by TOC analyzer, the 15N abundance of each sample was employed to analyze by isotope mass spectrometer. The main results of the study was showed under paragraphs:1 The field experiments indicated that the maize yield of B20 was significantly decreased by 20.55%, compared with BO. NB20 which Compared with NBO significantly was enhanced the root activity, promoting the accumulation of dry matter from maize. Maize grain quality of NB20 was increased, which the yield was promoted by 6.07%. Due to the excessive decline of soil bulk density, seedling emergence rate was reduced by NB40-treated. The C/N of soil which was increased excessively contributed to the phenomenon that microorganism fought with maize for nitrogen absorption. Finally, the maize kernels quality was decreased with yield of maize reducing by 13.88%. The results indicated that growth and quality of maize related with biochar-treated and nitrogen fertilizer was promoted. But disposable large amount of biochar-treated (40 thm-2) is non-benefit for crop growth.2 Compared with BO, the maize nitrogen uptake of B20 was significantly decreased by 16.9%. Compared with NBO, the N uptake of NB20 was increased by 5.6%. And then NB40 was decreased by 15.3%. The nitrogen content in the maize grain was improved by biochar-treated. The maize grain nitrogen content of NB20 was increased by 17.13%. Biochar-appropriated could promote the absorption of N fertilizer, improving the utilization of nitrogen in the soil.3 Pot experiments indicated that compared with CK, Maize of NB-treated was significantly increased by 7.20%; comparing with CK, Nitrous Oxide emissions from soil was significantly decreased by 26.67%, nitrogen-leaching of wastage from soil was significantly decreased by 47.48%. The total reduction of soil nitrogen wastage was decreased by 34.11%. Biochar-appropriated which matched wtih nitrogen fertilizer could increase nitrogen of utilization, emit Nitrous Oxide and reduce the leaching loss of nitrogen.4 Pot experiments of 15N indicated that the absorption of fertilizer which was tabbed by 15N from NB-treated was decreased by 7.98%. In the other hands, nitrogen utilization efficiency was decreased by 3.6%; 15N fertilizer residue was increased by 17.03%, Residual ratio was increased by 6.4%. The wastage of fertilizer which was tabbed by 15N was decreased by 27.55% and the loss rate was decreased by 3.7%. Visible, biochar-treated reduced notablely nitrogen fertilizer availability, increasing the immobilization of nitrogen fertilizer in soil, reducing the ammonia volatilization and leaching, and Nitrous Oxide emissions.In conclusion, biochar-appropriated which dealed with N fertilizer promoted maize absorption of nitrogen and increasing maize yield. Biochar-treated could reduce the loss of nitrogen leaching and nitrous oxide emission, as well as decreasing N fertilizer of chemical fertilizer utilization rate in current season and persistence of N in the soil, promoting the availability of N from the soil and transfertation of N into the plant. These results could create conditions for reducing fertilizer application.