Responses Of Wheat Field Soil Respiration And Wheat Productivity To Biochar Application

At present,the problems of global warming and unreasonable utilization of crop straw resources are still prominent.Exploring the emission reduction mechanism and efficient utilization of farmland resources in the process of crop production has become a hot and difficult point in crop science research.In order to further clarify the effect of straw biochar application on farmland ecological environment and the formation of winter wheat yield,the wheat field biochar application experiment was carried out in Guanzhong irrigation area from October 2018 to June 2021.The biochar application levels were set up in the experiment as follows:0 t·hm^-2·a^-1（C0）、10 t·hm^-2·a^-1（C10）、20 t·hm^-2·a^-1（C20）.By analyzing the effects of different biochar application rates on soil hydrothermal factors,soil respiration,soil enzyme activities,and winter wheat growth and yield in wheat fields,it is expected to provide theoretical basis and technical support for farmland carbon sequestration,emission reduction and soil health management.The main research results are as follows:（1）The application of biochar significantly increased the soil water content of 0-20 cm and 20-40 cm during the growth period,and the increase of C20 was the largest,while the effect on the soil water of 40-60 cm was less.During the whole experiment period,compared with C0,the soil water content of C10 and C20 increased by 2%to 59%and 7%to 66%in the0-20 cm soil layer,respectively,while that of 20-40 cm increased by 12.5%to 31.7%and 15.2%to 35.4%,the three years average soil water content in the 0-60 cm soil layer of each treatment is in the order:C20（20.11%）>C10（19.01%）>C0（15.14%）.As the same time,biochar weakened the variation range of soil moisture in 0-60 cm,and it has a stable water retention effect.（2）The change law of soil respiration during wheat growth period was as follows:soil respiration rate was low from seedling stage to greening stage,rapidly increased from jointing to heading stage,maintained at a high level from heading to grain filling stage,and decreased during mature stage.There were significant differences in soil respiration rate among treatments at different growth stages（P<0.05）.Biochar application reduced soil respiration rate in winter wheat field and cumulative soil CO₂ cumulative emissions during the whole growth period of winter wheat.Compared with C0 in 2018-2019,2019-2020 and 2020-2021,the average soil respiration rates of C10 and C20 decreased by 32.2%,18.5%,15.4%,5.7%,27.9%and 9.9%,while the cumulative soil CO₂ emissions of C10 and C20 decreased by 31.6%,19.3%,16.7%,8.8%,25.1%and 12.3%,respectively.Soil temperature is the main factor affecting the seasonal variation of soil respiration,and the exponential function R_s=ae^bT can better fit the relationship between soil temperature and soil respiration.There was no significant correlation between soil respiration and 0-60 cm soil water content.In this study,the temperature sensitivity(Q₁₀)of soil respiration was between 3.25 and 4.11.The application of biochar increased the Q₁₀,which was C20>C10>C0,and the Q₁₀ also showed a certain increasing trend with the increase of soil depth.（3）The soil urease activity increased significantly with the increase of biochar application,and the activity in flowering stage was higher than that in mature stage.Compared with C0 in the two years of 2018-2019 and 2019-2020,the growth rates of C10 and C20 were 5.8%～11.1%and 15.5%～34.1%,respectively.Application of biochar reduced the activity of catalase in soil.From 2018 to 2019,biochar significantly decreased the activity of catalase at anthesis and mature stages（P<0.05）.Compared with C0,C10 and C20 decreased by 6.6%,6.2%in anthesis stage,respectively,and decreased by 10.5%and 7.2%in mature stage.The same pattern from2019 to 2020,the application of biochar decreased by 4.5%（C10）and 1.4%（C20）at anthesis stage,respectively,and the mature stage was reduced by 6.9%（C10）and 2.4%（C20）.The soil invertase activity decreased significantly with the increase of biochar application rate.Two years in 2018-2019 and 2019-2020 were C0>C10>C20.Compared with C0,C10 and C20decreased by 4.3%～7.9%and 11.5%～21.1%respectively.Compared with C0,C10 increased by 6.0%and 3.8%,while C20 decreased by 35.8%and 34.3%,respectively,during anthesis and mature stage in 2018-2019.Compared with C0,C10 increased by 3.5%and 1.9%,while C20 decreased by 23.2%and 24%in 2019-2020 during anthesis and mature stage,respectively.（4）The application of biochar slightly increased the plant height,leaf area index and SPAD value of winter wheat,but the difference between treatments was not significant.At the same time,the application of biochar significantly increased the above-ground dry matter mass of winter wheat.From 2018 to 2019,the above-ground biomass in each growth period showed the order of C20>C10>C0,compared with C0,the increase range of C10 and C20 was0.3%～5.4%and 7.8%～14.7%,respectively,and the difference between treatments was not significant.From 2019 to 2020,C10 and C20 increased by 6.5%,10.0%,1.4%,8.1%,0.3%,7.8%,1.9%,and 9.3%,respectively,compared with C0 at the anthesis,grouting and maturing stages.The performance in 2020-2021 is C20>C10>C0.The application of biochar promoted the increase of winter wheat yield,and the increase of grain yield was mainly achieved by increasing the number of panicles per unit area.From 2018 to 2019,compared with the C0,the yields of C10 and C20 increased by 1.9%and 3.6%,respectively.The yields of winter wheat in 2019-2020 and 2020-2021 showed a variation pattern of C10>C20>C0,respectively.The yields increased by 8.5%,5.9%,9.4%,5.92%.In conclusion,application of biochar can improve soil water and heat conditions in Guanzhong area,reduce soil respiration,and increase winter wheat yield,but it increases the temperature sensitivity of soil respiration.Among them,the carbon application rate of 10 t·hm^-2·a^-1（C10）showed the best effect in taking into account the yield of winter wheat and reducing soil carbon emissions in farmland.