Influence Of Biochar On Nitrogen And Phosphorus Leaching And Growth In Summer Maize Field

Due to the excessive application of water and fertilizer,the leaching of nitrogen and phosphorus from farmland becomes more and more serious,and the problems of soil pollution and water pollution become increasingly apparent.These questions seriously affect the agricultural development and food security in China.In recent years,the application of biochar to soil improvement in farmland has been increasingly studied.However,because of the raw materials,application amount,soil types,crop types and other environmental factors,the effects of biochar on soil moisture,fertility and crop yield are significantly different.In view of this,summer maize was taken as the research object,and the field experiment was carried out in Changqing of Shandong Province.Three water and fertilizer management schemes was set up:I1N1（I1:67.5 mm,N1:150 kg/hm²）,I1N2（I1:67.5 mm,N2:200kg/hm²）and I2N2（I2:121.5 mm,N2:200 kg/hm²）.In order to investigate the effect of biochar on the distribution characteristics of soil moisture content,nitrogen（N）and phosphorus（P）content,crop growth indexes and yield,three different biochar application treatments（C0:0t/hm²,C1:20 t/hm²,C2:40 t/hm²）was set up in each water and fertilizer management scheme.The research conclusions are as follows:（1）Biochar application can reduce bulk density at the surface soil and improve soil field water capacity.The change of soil volume moisture content is mainly in 0-60cm soil layer,and the surface soil moisture content is mainly affected by biochar and fertilizer amount.The content of NO₃^--N,NH₄⁺-N and P in biochar application treatment is significantly higher than that in non biochar application treatment.The results showed that the application of biochar could reduce the leaching loss of NO₃^--N,NH₄⁺-N and P.The concentrations of NO₃^--N,NH₄⁺-N and P in soil leaching solution with biochar application were significantly lower than those without biochar application.The peak time of NH₄⁺-N concentration in soil leaching solution with biochar application would be delayed.（2）The LAI of summer maize was significantly affected by biochar at jointing stage.Under the same irrigation and fertilizer treatment,the LAI increased with the increase of biochar application rate.C2 was 13.01%-36.20%higher than C1 and 55.66%-74.80%higher than C0.The increase of water and fertilizer would enhance the promoting effect of biochar on the LAI.The inhibition effect of biochar on plant height and stem diameter was mainly in the seedling stage and jointing stage,while the inhibition effect of biochar on plant height and stem diameter disappeared at filling stage and mature stage.Biochar could delay the stem wilt of summer maize,mainly by promoting the growth of plant height and stem diameter in the late growth period.In general,the growth indexes of I2N2C1were the best.I2N2C1 were the most beneficial for dry matter accumulation,and biochar application could significantly increase the number of grains per spike.The yield of treatment with biochar was16.12-46.67%higher than that without biochar application.Under the treatments of I1N1 and I1N2,the yield increased with the increase of biochar application rate.Under the treatment of I2N2,the yield under the treatment of C1 was the highest.（3）The content of SPAD was affected by biochar application.The content of SPAD increased with the increase of the application amount of biochar.The SPAD of I1N1C2 was57.32,and I1N1C2 was beneficial to delay the time of withering and yellowing of maize leaves.Biochar application can improve the photosynthesis of summer maize,which was mainly manifested by the increase of net photosynthetic rate（P_n）,transpiration rate（T_r）and stomatal conductance（G_s）,and the decrease of intercellular CO₂concentration（C_i）.P_nhad a close relationship with C_i,which showed a close negative correlation before maturity.P_nwas more affected by SPAD after maturity.T_rand G_sshowed a close positive correlation at jointing tasseling stage,and increased with the increase of biochar application rate under the same water and fertilizer conditions.（4）Under different water and fertilizer levels,the most suitable amount of biochar was different,but biochar application was helpful to improve the efficiency of water and fertilizer utilization and economic benefits.Through evaluation and analysis,the efficiency of water and fertilizer utilization and economic benefits of I2N2C1 were the highest and reached24592 yuan/hm²and 21088 yuan/hm²,respectively.Therefore,I2N2C1（I2:121.5 mm,N2:200 kg/hm²,C1:40 t/hm²）was used as the optimized combined application scheme of biochar and water and fertilizer.