| In order to explore the carbon sequestration and emission reduction effects of biochar on soil,four levels of biochar application,CK(0t·ha-1·yr-1),T1(1.5t·ha-1·yr-1),T2(15t·ha-1·yr-1),T3(45t·ha-1·yr-1),were set up in the tobacco field ecosystem of Xuchang Campus of Henan Agricultural University.The dynamic changes of soil respiration,soil hydrothermal factors,soil organic carbon and its active carbon components in flue-cured tobacco growing season were measured under different amounts of biochar application.At the same time,five biochar application levels,CK(Og/kg-1),T1(4g/kg-1),T2(40g/kg-1),T3(80g/kg-1)and T4(120g/kg-1),were set up to monitor soil respiration in a short time.The short-term and long-term effects of biochar on soil respiration and the effects of long-term application of biochar on soil carbon pool were analyzed in order to provide data support and theoretical basis for carbon sequestration and emission reduction effects of biochar.The main results are as follows:1.Biochar significantly affected the soil respiration rate.The total soil respiration rate of all treatments increased at first and then decreased during the growing season.The total soil respiration rate of all treatments showed T3>CK>T1>T2 during the growing period of flue-cured tobacco in the field.Among them,T1 and T2 treatments decreased the soil respiration rate compared with CK,and T2 treatments reached a significant level,while T3 treatments significantly increased the soil respiration rate.2.The effects of biochar application on soil respiration are different in different stages.Different dosage of biochar significantly promoted soil respiration in the early stage of application,but the middle and low dosage of biochar(1.5t·ha-1·yr-1 and 15t·ha-1·yr-1)gradually showed the effect of inhibiting soil respiration with the passage of time,and the T2 treatment reached a significant level;the high dosage of biochar(45t·ha-1·yr-1)promoted soil respiration throughout the growth period.Short-term incubation experiments in laboratory showed that biochar significantly promoted soil respiration in a short period of time.With the passage of incubation time,the differences between treatments gradually weakened,and the dynamic changes of soil respiration in each treatment tended to be consistent.There was no significant difference in average soil respiration among treatments during the incubation period.3.In the growing season of Flue-cured tobacco,T2 treatment significantly reduced the rate of soil heterotrophic respiration and the proportion of heterotrophic respiration in total soil respiration,while T3 treatment significantly increased the proportion of soil heterotrophic respiration and total soil respiration.T1 and T2 treatments significantly reduced soil autotrophic respiration,and T2 reached a significant level;T3 treatment significantly increased soil autotrophic respiration.T1 and T2 treatments significantly increased the proportion of soil autotrophic respiration,while T3 treatments significantly reduced the proportion of soil autotrophic respiration.4.The influence of soil 5cm temperature on soil respiration was 55%and 65%.There was a significant correlation between them(P<0.01),but the relationship between soil respiration and soil 5cm humidity was not obvious.T1 and T2 treatments significantly reduced the soil respiration temperature sensitivity index(Qio),while T3 treatments significantly increased the soil respiration temperature sensitivity index.5.Biochar application significantly increased soil organic carbon content,soil carbon pool index and soil carbon pool management index,and increased with the increase of biochar application.Microbial biomass carbon(MBC),soluble organic carbon(DOC)and oxidizable organic carbon(ROC)were T3>T1>T2>CK in all treatments.Bi,char treatment significantly increased MBC at 30 and 90 days after transplantation,and there was no significant difference in the average MBC of Flue-cured Tobacco during the growing season among the treatments.T3 treatment significantly increased DOC.Biochar application significantly increased ROC 30 days after transplantation and decreased microbial entropy(MQ).T1 and T2 treatments increased soil microbial metabolic entropy(qCO2),while T3 treatments increased qCO2.Biochar application had no significant effect on DOC/SOC and ROC/SOC.In summary,different dosages of biochar are beneficial to soil carbon sequestration,and medium and low doses of biochar are more conducive to improving the utilization of carbon sources.At the same time,low and medium doses of biochar application can significantly reduce soil carbon emissions,and the effect of medium doses of biochar application is the best.Therefore,according to the results of this study,it is suggested that the amount of biochar application is 15t·ha-1·yr-1,which is most conducive to soil carbon sequestration and emission reduction. |
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