Simulation Study On Inorganic Nitrogen And Humic Acid Composition Of Degraded Black Soil By Adding Organic Materials

Black soil is a precious natural resource and an important guarantee of food security in China.With the increasing pressure of grain production,the single farming method and unreasonable fertilization lead to the serious degradation of black soil,the significant decrease of organic matter content and the low utilization rate of nitrogen fertilizer.It is of great significance to maintain and improve the productivity of black soil for ensuring food security.In this paper,the degradation of black soil as the research object,the indoor culture method was used to study the transformation of soil inorganic nitrogen and the change of humus components under the treatment of biochar,straw and organic fertilizer,in order to provide scientific basis for the application of organic materials to improve the soil fertility,rational use of resources and improve the productivity of black soil.Biochar?B?,organic fertilizer?O?and straw?S?were added to the black soil respectively.The carbon content levels were 5.98 g·kg^-1?11.96 g·kg^-1?23.92 g·kg^-1and 35.88 g·kg^-1,respectively.The culture time was 60d at 25?.?1?NH₄⁺-N content increased first and then decreased with the increase of culture time,while NO₃^--N content increased with the increase of culture time.Straw and organic fertilizer treatment can increase the content of NH⁺_4f-N in soil,but the content of NH⁺_4f-N in biochar treatment is slightly lower than CK treatment.?2?Adding biochar,straw and organic fertilizer could increase the release of soil mineralized carbon,and with the extension of culture time and the increase of carbon application level,the mineralization rate gradually decreased with the increase of culture time;the mineralization accumulation of organic carbon was in accordance with the first-order dynamic equation proposed by Stanford and Smith?R²>0.98?.In addition to biological carbon treatment,B1 is used to treat organic carbon ore.The other treatments had positive excitation effect first and then negative excitation effect;straw and organic fertilizer treatments had positive excitation effect on soil mineralization.?3?Three dimensional fluorescence spectrum analysis showed that adding biochar,straw and organic fertilizer significantly affected the humic acid composition,and the effect on fulvic acid was greater than humic acid.Among the three components of fulvic acid,biochar and straw treatment promoted the accumulation of aromatic protein and fulvic acid like substances,while organic fertilizer treatment promoted the accumulation of humic acid like substances in addition to the above two substances,forming more complex substances.?4?Adding biochar,straw and organic fertilizer significantly affected the change of soil enzyme activity.The enzyme activity increased with the increase of application level.Among them,straw treatment is the most important to promote urease activity,followed by organic fertilizer and biochar treatment;organic fertilizer treatment is the most important to affect nitrate reductase,followed by straw and biochar treatment;biochar treatment is the most important to affect catalase,followed by organic fertilizer and straw treatment;straw treatment is the most important to affect invertase,followed by organic fertilizer and biochar treatment.