Effects Of Nitrogen Reduction Combined With Humic Acid And Biochar On Soil Physical And Chemical Properties And Nutrient Absorption Of Maize

In view of the degradation of the quality of meadow black soil farmland,heavy texture,poor ventilation and water permeability,resulting in low fertilizer utilization rate and low maize yield.In order to provide theoretical basis for the selection of optimal fertilization mode of meadow black soil,the optimal ratio of humic acid,biochar and inorganic fertilizer was studied by applying biochar and humic acid under the condition of nitrogen reduction.The main maize variety"Xianyu335"was used as experimental material in the field experiment on meadow black soil,including 11treatments（N is Nitrogen,H is Humic acid,B is Biochar）:no fertilization（CK）,conventional fertilization(N₁₀₀H₀),reduced application of nitrogen fertilizer 20%+5 t·hm^-2 humic acid(N₈₀H₅),reduced application of nitrogen fertilizer 20%+10 t·hm^-2 humic acid(N₈₀H₁₀),reduced application of nitrogen fertilizer 30%+5 t·hm^-2 humic acid(N₇₀H₅),reduced application of nitrogen fertilizer 30%+10 t·hm^-2humic acid(N₇₀H₁₀),conventional fertilization(N₁₀₀B₀),reduced application of nitrogen fertilizer 20%+5 t·hm^-2 biochar(N₈₀B₅),reduced application of nitrogen fertilizer 20%+10 t·hm^-2biochar(N₈₀B₁₀),reduced application of nitrogen fertilizer30%+5 t·hm^-2 biochar(N₇₀B₅),reduced application of nitrogen fertilizer 30%+10 t·hm^-2biochar(N₇₀B₁₀).The effects of combined application of biochar and humic acid on soil permeability,soil water and fertilizer retention capacity,crop nutrient absorption,yield formation and nitrogen use efficiency were studied.The results show that:（1）Humic acid and biochar have positive effects on improving soil physical properties.Compared with conventional fertilization,humic acid and biochar can significantly reduce soil bulk density,increase soil porosity,increase soil saturated water content and field water holding capacity.The results show that the combination of humic acid and biochar can enhance soil permeability and water holding capacity,and the improvement effect of high amount of humic acid and biochar treatment is better.（2）Nitrogen reduction combined with humic acid and biochar significantly increased the content of available nutrients in mature soil.The results showed that N₈₀H₁₀ was the best treatment in humic acid application.Compared with conventional fertilization,N₈₀H₁₀ increased soil alkali hydrolyzable nitrogen content by 5.69%（P<0.05）,soil available potassium content by 7.58%（P<0.05）,and soil available phosphorus content by 10.13%（P<0.05）.Compared with conventional fertilization,N₈₀B₁₀ increased soil alkali hydrolyzable nitrogen content by 6.34%（P<0.05）,soil available potassium content by 9.60%（P<0.05）,and soil available phosphorus content by 14.20%（P<0.05）（3）Compared with conventional fertilization,N₈₀H₅,N₈₀H₁₀,N₇₀H₅and N₇₀H₁₀ treatments decreased by 10.48%,16.48%,13.80%and 14.46%（P<0.05）.Compared with conventional fertilization,N₈₀B₅,N₈₀B₁₀,N₇₀B₅and N₇₀B₁₀ treatments increased 9.13%,8.68%,4.18%and 7.44%（P>0.05）respectively.（4）Nitrogen reduction combined with humic acid and biochar could promote the nutrient accumulation of maize seeds.N₈₀H₁₀ was the most effective treatment in reducing nitrogen and applying humic acid,and the accumulation of nitrogen,phosphorus and potassium increased by9.24%,15.22%and 18.78%respectively.N₈₀B₁₀ had the most significant effect in the treatments of reducing nitrogen and applying biochar,and the accumulation of nitrogen,phosphorus and potassium in grain increased by 9.63%,19.50%and 6.31%respectively.（5）The application of humic acid and biochar can promote the formation and development of root system to a certain extent.Compared with conventional fertilization,the application of humic acid and biochar can effectively promote the increase of root length,root tip number,root surface area,root volume,average root diameter and root dry weight of maize seedlings,and it will increase with the increase of application amount.increase.Among them,the root volume of each treatment with humic acid increased the most significantly,and the increase range was between24.18%and 32.97%.It is beneficial to improve the nutrient absorption capacity of crops and contribute to the growth of the above-ground parts of plants.（6）Nitrogen reduction combined with humic acid and biochar could promote the dry matter accumulation of maize seeds.Compared with conventional fertilization,N₈₀H₁₀ and N₇₀H₁₀ with high humic acid increased by 8.73%and 6.38%respectively,reaching significant difference.Compared with N₁₀₀B₀ treatment,N₈₀B₅,N₈₀B₁₀,N₇₀B₅ and N₇₀B₁₀ treatments with biochar application increased grain dry matter accumulation by 6.80%,11.05%,4.96%and 9.49%,respectively,with significant increase in N₈₀B₅,N₈₀B₁₀ and N₇₀B₁₀ treatments.（7）Nitrogen reduction combined with enough humic acid or biochar could improve maize yield and nitrogen use efficiency.Compared with conventional fertilization,the maize yield of N₈₀H₁₀ and N₇₀H₁₀with high humic acid application increased by 11.33%and 2.24%respectively,while the maize yield of N₈₀H₅ and N₇₀H₅ with low humic acid application decreased.The highest yield of N₈₀H₁₀ was 11303kg·hm^-2.The yield of the treatment of reducing nitrogen fertilizer combined with high amount of biochar was significantly higher than that of conventional fertilization.Compared with N₁₀₀B₀,the yield of N₈₀B₁₀ and N₇₀B₁₀ increased by 15.83%and4.38%respectively,and the yield of N₈₀B₁₀ was the highest,reaching 11861kg·hm^-2.Reducing nitrogen and increasing humic acid and biochar can effectively improve nitrogen use efficiency of maize.Compared with conventional fertilization,humic acid treatment increased by 36.16%～60.22%（P<0.05）,and N₇₀H₁₀treatment was the best.Compared with conventional fertilization,biochar application increased by 70.53%～78.94%（P<0.05）,and N₈₀B₁₀ treatment was the best.