Effects Of Different Organic Material Additions On Soil Aggregation And Organic Carbon Sequestration In Reductive Soil Disinfestation

In recent years,with the expansion of planting area and the extension of service life,the obstacle of continuous cropping of protected soil crops in China is becoming more and more serious.As a green and efficient soil remediation technology,Reduced Soil Disinfestation（RSD）has been widely used in protected cultivation.However,a large number of studies have focused on its remediation effect on soil,while ignoring the soil organic carbon（SOC）,which is equally important for improving soil physical and chemical properties and alleviating continuous cropping obstacles.Therefore,it is of great significance to study the SOC sequestration and soil aggregate in the process of using RSD technology.Therefore,this study selected degraded facility soil as the research object,and carried out two indoor culture experiments and one field experiment to explore the effects of different organic materials on soil aggregates and organic carbon sequestration.The main conclusions are as follows:The effects of biochar and chemical fertilizer on SOC sequestration in RSD technology were studied through a 28-day indoor culture experiment.The results showed that the higher microbial activity caused by biochar（Fig.2-7）increased the newly formed SOC by 111.1%and 120.3%compared with the treatment without biochar（Fig.2-4）,while its lower enzyme activity inhibited the mineralization of the original SOC;In the treatment without biochar,the original SOC decreased by 12.6%and 12.6%during aerobic period due to its higher enzyme activity,which led to the increase of SOC content by 24.5%（P<0.001）compared with that without biochar at the end of culture,while the addition of biochar and nitrogen and phosphorus at the same time decreased SOC content by 4.4%（P<0.05）.At the end of culture,the addition of nitrogen and phosphorus significantly increased the activities of glucosidase（BG）,xylosidase（BXYL）and polyphenol oxidase（PPO）by 47.2%,48.2%and 53.7%（P<0.01）,while the addition of biochar decreased the activities of BG,BXYL and PPO by51.5%,72.6%and 41.7%.The soil conductivity and NO₃^--N content of the four RSD treatments decreased by 49.3%,48.6%,45.1%and 45.1%respectively;90.0%,83.8%,82.5%and 79.2%（P<0.01）.The effect of straw decomposing agent on RSD technology on soil aggregates was studied through a 28-day incubation experiment.The results showed that compared with CK,both RSD treatments promoted the process of soil aggregation,and the mass proportions of large-macroaggregates and small-macroaggregates increased by 18.1%,18.8%and 27.8%,7.4%respectively.Accordingly,the mass proportions of micro aggregates and silt+clay decreased by 10.8%,22.9%and 8.1%,27.0%,respectively;The straw decomposition agent further increased the mass proportion of coarse aggregates and micro aggregates treated with rsd-a by 9.7%and 2.8%.Accordingly,the mass proportion of small-macroaggregates and silt+clay decreased by 11.4%and4.11%.The SOC content of the two RSD treatments increased by 15.5%and 21.3%respectively compared with CK.Compared with CK,the two RSD treatments increased the SOC contents of micro aggregates and silt+clay by 14.3%,44.1%,12.6%and17.0%,respectively.In addition,the addition of straw decomposing agent increased the SOC content of each particle size aggregate by 9%,25%,26%and 4%,respectively.Compared with CK,both RSD treatments decreased soil conductivity and NO₃^--N content by 81.5%,80.5%,90.3%and 90.4%respectively,and increased NH₄⁺-N content by 8.5 mg/kg and 8.3 mg/kg.Field experiments were conducted to study the effect of RSD technology on carbon sequestration and salt removal in practical production.In 0-20 cm soil layer,compared with that before treatment,W,CB and WCB treatment decreased soil p H value,electrical conductivity,NO₃^--N content,total salt content and increased SOC content by 20.0%,16.3%and 6.5%.In conclusion,RSD treatment with organic materials such as corn straw,weeds and big trumpet stage corn plants can effectively improve SOC content,reduce soil NO₃^--N and other salt content and electrical conductivity,alleviate soil salinization in greenhouses with continuous cropping obstacles and increase SOC sequestration.In addition,RSD treatment with corn straw as organic material can promote the process of soil aggregation,improve the proportion of water stable macroaggregates and increase the water stability of aggregates.In the process of RSD treatment,the addition of biochar accelerated the production of newly formed SOC,reduced the mineralization loss of native SOC,and was more conducive to the accumulation of SOC;Although the addition of nitrogen and phosphorus increased the activity of C-conversion enzyme and accelerated the turnover of SOC,it had no significant effect on the sequestration of SOC;Adding straw decomposing agent can further promote the process of soil aggregation and improve the water stability of aggregates.