Effects Of Biochar Amendment On Double Rice Yield,soil Physical And Chemical Properties And Its Aftereffects

Rice occupies an important position in China’s grain production and is one of the main grain crops in China.Soil quality problems such as paddy soil acidification and low fertilizer utilization rate severely restrict the continuous stable and high yield of double-season rice in China.Therefore,it is of great significance to explore how to improve the quality of paddy soil in China.In recent years,biochar has been extensively studied as an ideal improver for acid soils,however,there are few studies on the application of double-season rice fields in the south.To this end,this study explored the effects of nitrogen fertilizers（N₀,N₁）combined with different amounts of biochar（B₀:0t/hm²、B₁:20 t/hm²、B₂:40 t/hm²）on yield formation,soil physical and chemical properties,nitrogen uptake and greenhouse effect in paddy fields through a three-year field experiment.To further clarify the aftereffects of applying biochar,a new biochar treatment（F for new application,FB₁,FB₂）was added to the conventional fertilization community in2019,and a comparative analysis of the new biochar application in 2019 and the biological application in 2017 Differences in the effects of carbon（B₁,B₂）on rice growth and soil physical and chemical properties.The main findings are as follows:1.Nitrogen fertilizer combined with biochar can significantly increase the yield of early and late rice in 2017,but there is no trend of increasing yield for early and late rice in2018 and 2019.Analysis of variance showed that the application of nitrogen fertilizer and biochar（C×N）had no significant interaction effect on the yield of early and late rice,while the application of biochar and year（C×Y）had a significant interaction effect on the yield of early and late rice.The application of biochar significantly increased the nitrogen absorption of early and late rice in 2017,and there was no increase in nitrogen absorption in 2018 and 2019.The application of biochar can increase soil total nitrogen,organic carbon,p H and available potassium content in varying degrees.2.Both the newly applied biochar（FB₁,FB₂）in 2019 and the biochar（B₁,B₂）applied in 2017 can significantly increase the soil organic carbon,p H and available potassium content,but the increase rate of biochar applied in 2017 is lower than that of the new application biochar.Compared with the control,the new application of biochar can significantly improve the yield of early and late rice and above-ground dry matter,while the application of biochar in 2017 did not significantly increase the yield and above-ground dry matter of early and late rice.The new application of biochar can significantly increase the absorption of phosphorus and potassium in early and late rice,while the application of biochar in 2017 has no significant effect on the absorption of phosphorus in early and late rice.Only B₂significantly increased the absorption of potassium in late rice.In summary,the effect of biochar applied in 2017 on promoting rice growth and soil fertility is lower than that of new application of biochar.3.The application of biochar can significantly reduce the comprehensive greenhouse effect（GWP）and greenhouse gas intensity（GHGI）of the paddy field during the growth period of double-season rice.Under the conditions of nitrogen application and no nitrogen application,the application of biochar can significantly reduce the cumulative emissions of CH₄by 25.9%to 41.0%;the application of nitrogen fertilizer has no significant effect on the cumulative emissions of CH₄,but significantly increases the cumulative emissions of N₂O.Under the conditions of nitrogen application,the application of biochar can significantly increase the cumulative N₂O emissions from rice fields.Compared with N₁B₀,the cumulative N₂O emissions from N₁B₁and N₁B₂treatments increased by 109.93%and106.54%respectively.The comprehensive greenhouse effect of each treatment is N₁B₀>N₀B₀>N₀B₂>N₁B₁>N₁B₂in order from large to small.Compared with single application of nitrogen fertilizer,the combined application of nitrogen fertilizer and biochar is the best to alleviate the comprehensive greenhouse effect of double-season rice fields in southern China.