Research On The Relationships Between Maize Stover And Its Derived Biochar Application On Soil Aggregates

Northeast China is one of the main grain-producing area in China.In recent years,with the increasing population and the pressure of food security,soil had been severely cultivated and degraded.Soil aggregate is the basic unit of soil structure,soil aggregate also provides the storage site for soil organic carbon(SOC),nearly 90%of the SOC is located in soil aggregates in topsoil.Therefore,it is the key factor to keep the contents of soil aggregates to promote the level of SOC and fertility of soil.Northeast China is situated at one of the three gold maize belts of the world,so the stover resources is extremely abundant in the area.It is the suitable method to improve soil fertility by stover returned.However,the weather is not suitable for stover returned to soil in Northeast China.So it is a feasible way to convert stover resources to biochar and apply biochar to soil.Base on this background,field experiments were carried out in Northeast China.The effects of maize stover biochar on soil aggregates and carbon sequestration characteristics were systematically studied by long-term situated location field experiment.Short-term micro-plot experiment also studied to research the influence of biochar on soil aggregate and SOC in different soil types.The study contents and results are as follows:1 Effect of maize stover and its derived biochar on soil structure and organo-mineral complexesThe results of this long-term field study(five years)indicated that maize stover and its biochar application had significant effects on soil structure in Northeast China.Maize stover and its biochar affected the soil structure by increasing the soil macroaggregate(small macroaggregate)by 55.69%and 14.91%,respectively.However,differences were not observed in the aggregate stability between the biochar and stover treatments.In addition,the SOC were also increased by the biochar and stover amendments,increased by 34.26%and 24.07%.Biochar and stover application enhanced the SOC in macroaggregates and the relative contribution of organic carbon in small macroaggregates.These results demonstrate that the positive effect of biochar and stover on SOC occurs through soil aggregation.Both biochar and stover enhanced the QC to improve the macroaggregates contents,and the decreased DC under the biochar application may have been related to the stable characteristics of biochar.Our study demonstrated that organic amendments enhance the formation of macroaggregates by organo-mineral complexes,which might protect the SOC.Additional research is required on the different mechanisms between biochar and stover on organo-mineral complexes.Biochar and stover applications are both effective methods of improving the soil structure.2 Effects of maize stover and biochar on aggregate spatial distribution and carbon sequestration characteristics in Brown earthCompared with the same amount of carbonized stover,the effect of stover returning to the field was better.Both stover and biochar significantly improved the content and stability of soil aggregates in subsurface(20-40 cm)depth,and the content of macroaggregates increased by90.91%and 24.24%,respectively.At the depth of 40-60 cm,biochar still promoted the transformation of fine and fine aggregates(250-2000?m)and micro aggregates(53-250?m)correspondingly.Stover treatment also had corresponding effect.Compared with biochar treatment,the improvement of macro aggregate content and stability was more significant.The contents of fine and macro aggregates(250-2000?m)and micro aggregates(53-250?m)were significantly increased by 34.55%,61.39%and 48.71%,respectively.The results showed that both biochar and stover could improve soil structure and promote the sequestration of deep soil organic carbon.3 Long-term effect of a biochar amendment on soil aggregate stability and biological binding agents in brown earthAfter six consecutive years of maize planting,the content of soil small macroaggregates first increased and then decreased with the increase of biochar application rate.The content of soil fine aggregates varied from 27.71%to 34.99%,while the content of silt and clay was the lowest among all components,accounting for 14.75-23.72%.SOC,MBC,grspe and grspt were significantly increased under all biochar treatments.MBC decreased at first and then increased with biochar application.The results showed that biochar was the most suitable carbon fertilizer for improving soil structure.The content of SOC in large aggregates increased more.Biochar also increased soil p H,EC and CEC,as well as exchangeable Na~+and K~+.The content of exchangeable Na~+and K~+may be the reason for the decrease of macro aggregate content under the condition of high application rate of biochar.Therefore,biochar as a soil amendment might have the most suitable application rate.4 Short-term effect of biochar on soil aggregate and organic carbon in three distinct soil types(Aeolian soil,Coastal solonchak and Meadow soil)The effect of biochar on different types of soil was also different after two years of micro-plot experiment.In this study,the experimental results of biochar on Aeolian Sandy Soil for two consecutive years were quite different.In the first year,biochar could improve the content of soil macroaggregates and the stability of aggregates,while the biochar in the next year decreased the content of macroaggregates and the stability of water stable aggregates,and decreased the yield of peanut pods.The yields of C1 and C2 treatments decreased by 13.01%and 11.46%,respectively.Biochar promoted the formation of large aggregates and the formation of peanut pod yield in saline soil.The pod yield of C1 and C2 increased by 34.88%and 44.32%,respectively.The effect of biochar on the yield of crops grown on meadow soil was different from that of the two soils mentioned above.In two consecutive years,the effect of biochar on crop yield increased.5 Short-term effect of biochar on soil aggregate distribution and SOC contents in three distinct soils(Albic soil,Fluvo-aquic soil and Grey desert soil)Biochar has the ability to improve the soil structure of three different textures of albic soil,fluvo aquic soil and grey desert soil in a short time.In two consecutive years of experiments,biochar showed the ability to improve soil aggregates.Biochar reduced the content of clay components in Albic soil powder,which decreased by 40.68%and 36.67%in C1 and C2treatments,respectively.Due to the existence of dense albic layer,biochar had no significant effect on deep aggregates;biochar significantly increased the content of coarse aggregates in the surface layer of fluvo aquic soil,and C1 and C2 treatments significantly increased the content of coarse aggregates in fluvo aquic soil by 92.36%and 36.67%respectively There was no significant difference between C1 and C2(P<0.05).The stability of aggregates MWD,GMD and macroaggregate content were also significantly improved.Biochar promoted the formation of micro aggregates and fine aggregates in grey desert soil,and reduced the content of silt and clay.The content of silt and clay decreased by 45.33%and 36.71%under C1 and C2treatments,respectively.In this study,biochar as a soil amendment showed a good effect.In the long-term experiment of brown soil,returning the same amount of stover and biochar increased the content and stability of macro aggregates.Biochar can also promote the formation of macro aggregates by promoting the secretion of bio cement in soil.The application amount of biochar should be determined according to different environmental conditions.In this study,biochar has a certain universality.In addition to the texture and loose aeolian sandy soil,saline soil,meadow soil,fluvo aquic soil and grey desert soil all show positive effects of biochar on improving soil structure.