Effects Of Straw Return Forms On Soil Biological Functional Groups And Crop Growth

Global warming is a contemporary global issue that requires a coordinated global response.Carbon neutrality is one of the important measures to achieve emission reduction goals.Returning straw to the field is a way of recycling agricultural wastes,which can achieve the carbon neutrality goal to a certain extent.The high-temperature oxygen-free carbonization of straw into biochar is a new method of straw utilization.At the same time,soil nematodes are an important group of soil animals,which are widely distributed in various soil types around the world and play an important role in the stability and function of soil ecosystems.Currently,most of the research on straw and biochar returning to the field is based on soil negotiation dynamics,and it is not well integrated with straw and biochar for research.As a good ecological indicator group,soil biota is very necessary to conduct integrated research.Therefore,this experiment was conducted in situ in a paddy field of aquic brown soil in Northeast China,with three treatment groups and a control:(1)the control was not subjected to straw returning or biomass carbon addition(CK);(2)Full straw returned treatment(ST),which mean that all the rice straw produced in the plot in the previous year would be returned to the field;(3)All straw carbonization treatment(BC): all rice straw with the same quality as that in ST treatment was carbonized into biomass charcoal at high temperature and oxygen free,and then applied to the soil;(4)Half straw returning to field(50% ST)+half carbonization(50% BC)treatment(MX).To provide theoretical and data basis for exploring the impact of different straw return forms on soil biological functional groups,soil carbon and nitrogen dynamics,and crop growth.We found that applying biochar to farmland could increase soil moisture content by up to 98.21%.Biochar also effectively mitigated the soil acidification caused by straw returning,resulting in a 69.31% increase in underground biomass after two consecutive years of straw returning,while biochar application led to a 20.44% increase in aboveground biomass.Furthermore,two consecutive years of applying biochar and straw returning,either separately or mixed,increased rice yield by 11.25%,15.30%,and 12.22%,respectively.However,straw returning could lead to carbon loss and turn the soil environment into a carbon source,resulting in a significant increase in soil respiration by 351.47%after two years of treatment.Biochar,on the other hand,inhibited soil respiration by11.29%,and mixed application could increase soil respiration by 196.16%.These changes might be due to alterations in microbial heterotrophic and autotrophic respiration.Compared to the full amount of straw returning,mixing biochar with straw returning can effectively enhance the soil’s carbon sequestration ability.Two consecutive years of straw returning significantly increased soil nematode abundance by 286.87%,while mixing straw with biochar could achieve a similar effect,increasing it by 281.59%.However,external waterlogging stress could weaken the effect of straw and biochar returning on soil nematodes.Nematode distribution variedvary significantly during different field management periods,possibly due to some species’ inability to withstand waterlogging.However,the genus Rhabditis was dominant in all periods,indicating its strong resistance to interference.Straw returning had a downward control effect on the soil food web,while biochar returning had an upward control effect.Applying straw and biochar for several years could promote the structure and function of the agricultural soil ecosystem,while the mixed effect was slightly weaker.Therefore,in practical applications,mixing straw and biochar was a good measure for fertilization and soil improvement,enhancing the carbon sequestration ability of farmland.However,further research is needed to determine the optimal mixing ratio.