| The exploitation and utilization of coastal land resources is an important way to broaden the space for urban development and solve the demand for urban land.In order to solve the problems of soil salinization,poor structure,nutrient deficiency and low microbial activity in the coastal newly-reclaimed land,an integrated treatment of "organic fertilizer + microbial agent + rice planting" was proposed to enhance soil carbon pool,and rapidly improve the soil quality of the coastal newly-reclaimed land of Chongming Hengsha from April 2021 to November.Firstly,the combined effect of organic fertilizer and microbial agent was compared with the effect of application of microbial agent,and the rice varieties that were most suitable for growing in the soil of the coastal newly-reclaimed land of Chongming Hengsha were screened out,forming an operational technical scheme for rapid improvement of soil quality of the newly-reclaimed land.Secondly,studies were also carried out to explore the effects of interegrated measurement application for years and the follwed effects of that applied in the previous year on soil quality improvement.The main findings are as follows.(1)The combined effect of organic fertilizer and microbial agent decreased soil bulk density and mitigated the degree of soil salinization to facilitate plant growth.The concentrations of total nitrogen,alkaline hydrolyzable nitrogen,available phosphorus and available potassium in soil were increased,indicating soil nutrient improved.Soil physical composition showed a tendency to form large aggregates and improved the structure stability.The organic carbon content of soil aggregates within the size of 1～3 mm and >5 mm was increased,enhancing the carbon sequestration capacity of soil.The soil alkaline phosphatase activity,sucrase activity,microbial nitrogen and microbial carbon content were greatly improved and the rice yield was significantly higher than that of the control and the microbial-agent-applying field.(2)Comparing the effects among different rice varieties,it was found that Songzaoxiang1 had the best effect on soil salinization amelioration,soil aggregate stability,total nitrogen,alkaline phosphatase and sucrase activity improvemnent.Nanjing46 had the best effect on soil bulk density and porosity,maximizing the alkaline hydrolyzable nitrogen,total phosphorus,available potassium,soil aggregate organic carbon content and soil urease activity.Although Zhenghan10 had more advantages in increasing soil available phosphorus and total potassium,maximizing soil microbial nitrogen and microbial carbon content,rice yield was significantly lower than the other two varities.As a result,Nanjing46 and Songzaoxiang1 are more suitable to grow in the newly-reclaimed land.(3)The interegrated treatment application for years have improved the soil physical structure and increased the soil porosity.With the extension of soil improvement time,soil salinity continuously declined,the organic matter showed a trend to decrease first and then increase,while the soil total nitrogen,total phosphorus,alkaline hydrolyzable nitrogen and available phosphorus concentrations were greatly improved.It facilitated the soil particle transition from small aggregates to >5 mm ones,improving the stability of agglomerates and their organic carbon pool.With the extension of improvement time,the organic carbon concentration in aggregates showed a trend to increase,and so as to the soil carbon sequestration.At the same time,the activities of urease,alkaline phosphatase and sucrase were also improved significantly,as well as the nitrogen,microbiomass carbon and the biodiversity of soil bacterial,resulting in an increased rice yield year by year.The plots applying interegrated treatment in 2020 still had a positive effect on 2021 growing season(only using organic fertilizer but without any microbial agent)to alleviate soil salinization,improve total nitrogen,total phosphorus,soil aggregate stability and soil carbon sequestration capacity,and greatly promote rice yield. |
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