Effects Of Iron Fertilizer Combined With Biochar On Rice Field Greenhouse Gas Emissions,Soil Properties And Rice Yield

Rice fields are the main artificial source of agricultural greenhouse gas emissions in my country,and are also an important carbon sink.They have huge potential for carbon sequestration and emission reduction,and play a major role in achieving the goal of carbon peaking and carbon neutrality.The application of iron fertilizer and biochar has an effect on greenhouse gas emissions by affecting the physical and chemical properties of soil,but the appropriate ratio of iron fertilizer and biochar and its emission reduction effect and mechanism are worthy of further study.Therefore,this study carried out a field test in Beishan Town,Changsha County,Hunan Province from May to October 2021,setting up no application of biochar and iron fertilizer（T1）,single application of biochar 15t/hm²（T2）,single application of biochar Biochar 30t/hm²（T3）,single application of iron fertilizer0.3t/hm²（T4）,0.3t/hm² iron fertilizer+15t/hm² biochar（T5）,0.6t/hm² iron fertilizer+30t/hm² biochar（T6）,single application of iron fertilizer 0.6t/hm²（T7）,0.6t/hm² iron fertilizer+15t/hm² biochar（T8）,1.2t/hm² iron fertilizer+30t/hm² biochar（T9）,single iron application Fertilizer 1.2t/hm²（T10）10 treatments.The effects of combined application of iron fertilizer and biochar on rice field greenhouse gas emissions and soil characteristics were explored,in order to obtain the optimal ratio of iron fertilizer and biochar dosage,and provide a reference for the development of environmentally friendly,energy-saving and efficient rice field greenhouse gas emission reduction materials,below are key research findings:（1）The CH₄ emission in paddy fields peaked at the tillering,booting and full heading stages,and the peak emission in the tillering stage was the highest;the N₂O emission peak appeared in the early stage of rice growth,and reached the highest emission peak in the tillering stage;the CO₂ peak appeared in the full heading stage.Compared with the CH₄emission of T1,the emission reduction effect of T3 has reached a significant level.T9,T8,and T6 all have emission reduction effects.The reduction rates of seasonal cumulative emissions are 53.55%,20.47%,17.05%,and 5.40%,respectively.The average emission flux Compared with the N₂O emission of T1,the emission reduction effect of T7 has reached a significant level,and the reduction rates of seasonal cumulative emission and average emission flux are 10.98%and 8.76%,respectively.Compared with the CO₂ emission of T1,T8 treatment had the best emission reduction effect,followed by T7.The reduction rates of seasonal cumulative emission and average emission flux were 4.46%,1.00%and 3.57%,0.59%,respectively.Compared with T1,the warming potential of T3,T9,T8,and T6decreased by 36.30%,13.67%,10.58%,and 1.38%,respectively;the greenhouse gas emission intensity of T9,T8,T3,and T6 decreased by 40.91%,27.05%,and 26.02%,respectively.%and 4.00%.On the whole,the emission reduction effect of T8 and T9treatment is the best.（2）The total activity of soil catalase in rice growth stage was as follows:maturity stage>heading stage>milk maturity stage>tiller stage>booting stage,the total catalase activity in the mature stage was 77.08%higher than that in the booting stage.Compared with T1,T10treatment had the lowest catalase activity,and T3,T6 and T2 treatments increased catalase activity,and the increases were 8.73%,4.41%and 0.74%,respectively.The total activity of soil urease in the rice growth stage was as follows:tillering stage>booting stage>heading stage>mature stage>milk maturity stage.The urease activity increased by 6.68%,6.09%and 2.46%respectively.The catalase activity was the highest under the T3 treatment,and the urease activity was the highest under the T5 treatment.（3）Compared with T1,T9,T3 and T6 treatments all significantly increased the content of soil organic carbon,with an increase rate of 32.42%,28.51%and 28.13%,respectively;T10 treatment had the highest active organic carbon content,followed by T8,with an increase rate were 35.77%and 17.52%,respectively;T9,T3 and T6 treatments significantly increased the steady-state carbon content by 44.23%,34.19%and 32.42%,respectively;T10treatment had the highest carbon pool activity,followed by T7,followed by The increase rates were 73.33%and 53.33%,respectively;the carbon pool management index of T10treatment was the highest,followed by T7 and T2,with increases of 48.76%,34.98%and19.39%,respectively.（4）Compared with T1,T5 and T7 treatments at tillering stage increased the content of soil microbial biomass carbon in paddy field by 155.10%and 75.71%respectively;except for T7 and T2 treatments at full heading stage,the other treatments all increased soil microbial biomass in paddy field.In terms of carbon content,T5 had the best effect,with an increase of 77.15%;treatments of T6,T10 and T5 at the mature stage increased the content of soil microbial biomass carbon in paddy fields,with an increase of 107.03%,79.88%,and41.74%,respectively.（5）Compared with T1,all treatments increased the effective panicle number,seed setting rate and theoretical yield of rice,among which T3 treatment had the highest effective panicle number,an increase of 36.07%,and T5 treatment had the highest seed setting rate,an increase of 27.67%;The 1000-grain weight of T7 was the highest,followed by T7,with an increase of 3.43%and 1.78%,respectively;the actual yield of T9 was the highest,followed by T8,with an increase of 10.03%and 6.54%,mainly due to the improvement of effective panicle number and seed setting rate.Considering the effect of greenhouse gas emission reduction,soil property improvement and rice yield increase,T8（0.6t/hm² iron fertilizer+15t/hm² biochar）treatment performed the best.