Effects Of Straw Decomposing Agent Dosage On Wheat Straw Decomposition And Soil Greenhouse Gas Emissions

Long-term straw return to the field has led to changes in soil structure and stunted root growth of subsequent crops due to failure to decompose in a timely manner.The application of decomposition agent can promote stalk decay,maintain ground strength and achieve stable yield.Based on this,in the present study conducted a two-year field locational trial in which straw was returned to the field in full volume after the previous wheat crop was harvested,and four application rates of decomposition agents were set(T1:30 kg·hm^-2of decomposition agent,T2:45 kg·hm^-2of decomposition agent,T3:60 kg·hm^-2of decomposition agent,T4:75 kg·hm^-2of decomposition agent),and the straw was returned to the field without decomposition agent as the control（CK）.The decomposition rate and nutrient dynamics of the previous wheat straw,as well as soil physicochemical properties and greenhouse gas emission characteristics in the maize season were studied by nylon mesh bag method,which finally provided more scientific basis and field management strategies for screening the most suitable amount of decomposition agent for wheat straw return to the field and achieving the goal of sustainable soil and agricultural development.The research results are as follows:（1）Wheat stalks were decomposed after 100 d of summer maize season,and the decomposition rate gradually increased with increasing decay dose,with significant differences among treatments.The analysis of straw decay rate and straw decay rate showed that the final decay rate of turned buried straw was 60.58-69.28%for each treatment.T2 treatment could effectively accelerate the decay rate,and the final decay rate increased by 5.30%compared with CK,and its decay rate increased by 5.23-17.30%compared to CK during 80-100 d.The decay rate of hemi-cellulose was（46.68-58.73%）>cellulose（42.86-53.24%）>lignin（29.49-35.24%）.The highest effect of T2 and T4treatments on the decay of straw and its components.The magnitude of nutrient release rate all showed that potassium（89.29-94.31%）>carbon（78.90-85.77%）>phosphorus（53.45-63.00%）>nitrogen（56.90-62.77%）.T2 treatment could effectively improve straw C/N and Lignin/N,which were more suitable for straw decomposition.（2）The respiration rate of soil was enhanced by straw return with decomposition agent,which was accompanied by an increase in the amount of decomposition agent,and the soil respiration rate was smaller in T1 and T2 treatments.The correlation analysis showed that the accumulation dynamics of soil nutrients was highly correlated with the release of nutrients from straw,while each treatment of decomposition agent dosage had a certain enhancement effect on soil C/N.Compared to CK,T1,T2,T3 and T4 treatments increased the proportion of large-size soil aggregates by 30.47%,20.53%,19.94%and 19.22%,respectively.It also reduced the soil bulk density of 0-20 cm tillage layer.T3 treatment of soil capacitance reduced 9.33%compared to CK treatment in 0-10 cm layer and T4treatment reduced 3.97%compared to CK for 10-20 cm soil layer.Under the T4 treatment compared to CK,organic matter content,total nitrogen,alkaline soluble nitrogen,effective phosphorus and fast-acting potassium increased by 11.872%,10.43%,17.44%,82.51%and7.41%,respectively,at summer maize harvest stage.（3）Straw return with decomposition agent application increased the height of the summer maize.Compared with the CK treatment,the T3 and T4 treatments increased by17.57%and 10.91%,respectively,at 35 d after sowing.The application of decomposition agent significantly increased the rate of dry matter accumulation from flowering to mid-filling stage,and the maximum dry matter accumulation at harvest was concentrated under T2 and T3 treatments,at 332.71 and 328.77 g.The addition of straw decomposition agent had a significant effect on grain yield,with the highest yields of 12,293.78 and12,773.45 kg^-1·hm^-2of summer maize in T2 treatment.Application of decomposition agent could affect the ears length,grain number per spike and 100 grains weight of summer maize.The trend of increasing and then decreasing with the increase of decomposition agent dosage,with the T2 treatment having the best effect and significant differences among treatments.The effect on bald tip and stalk thickness was not significant.（4）N₂O emission fluxe peaked after fertilizer application and rainfall（irrigation）and decreased with summer maize reproductive process.The peak occurred mainly in the early reproductive stage,showing a single-peak curve variation,with the T4 treatment having the highest peak emission of 1.44 mg·m^-2·h^-1.Straw return with applied decomposition agent also promoted CH₄uptake,with the T1 and T2 treatments having the highest values of 5.04and 4.35 kg·hm^-2for CH₄.N₂O contributed the major GWP through on-farm economic benefit analysis.T4 treatment increased 81.81%compared to CK treatment.The highest net benefits were obtained with 18757.93 and 21551.77 Yuan·hm^-2in T2 treatment,respectively.In summary,through the study of the effects of straw return and decomposition agent application on wheat straw decomposition characteristics,soil physical and chemical properties,summer maize yield and integrated warming potential,45 kg·hm^-2treatment can obtain high economic benefits for summer maize while minimizing the environmental risks caused by the increase of greenhouse gas emissions due to decomposition agent addition,which has good economic-environmental benefits.Therefore,wheat straw return with 45kg·hm^-2of Renyuan Decomposing Agent is the best production model to ensure a productive and environmentally friendly summer maize.The results of the study are important for predicting future greenhouse gas emission trends under climate change conditions and formulating corresponding management measures for straw returning.