Study On Soil Nutrient Changes And Spatial Differentiation Of Cultivated Land Quality In Pingjiang County

Pingjiang County is located in the southeastern part of Yueyang City,Hunan Province.It is a county of the agricultural district of the south hilly mountainous agricultural and forestry area in the middle and lower reaches of Yangtze River zone.The grain production accounts for 1.7%of the total grain production of 122 counties and urban areas in the province.With the population increasing,rapid industrialization and urbanization,the contradiction between social development needs and shortage of cultivated land resources has become increasingly prominent.This study aims at spatial variation of cultivated land quantity and soil nutrient changes and quality level of cultivated land in Pingjiang County.The result can provide data support for the rational use of cultivated land resources and conservation and improvement of cultivated soil in Pingjiang County,and also provide scientific reference for decision making to adhere to the red line of cultivated land and ensure food security.This study analyzed the spatial variation characteristics of the change in the quantity of cultivated land,the change in soil nutrients and the current quality level of cultivated land in Pingjiang County based on the second soil census data,multiple years of cultivated land data,and cultivated land sample point data.The results are as follows.(1)Compared with 1980,The total cultivated land area in Pingjiang County in 2020increased by 1,331.39 hm~2,which is mainly due to the reporting method of cultivated land statistics during the second soil census,while the current remote sensing survey is used.Considering the different sources of cultivated land data during the second soil census period,only the rate of change of total cultivated land from 2010 to 2020 was analyzed,and the total cultivated land from 2010 to 2015 decreased by a total of 17,396.72 hm~2,with an average annual area decrease of 3,479.34 hm~2and a dynamic attitude of change of 4.19%;the total cultivated land from 2015 to 2020 decreased by a total of 15,433.14 hm~2and the average annual area decreased by 3,086.63 hm~2,with a dynamic degree of change of 4.70%(2)Since the second soil survey,the organic matter,effective phosphorus and fast-acting potassium content of rice soils in Pingjiang County have been on the rise.The average content of organic matter increased from 29.1g/kg to 33.2g/kg,an increase of14.01%;the average content of effective phosphorus increased significantly,from 5.6mg/kg to 23.7mg/kg,an increase of nearly three times;the average content of fast-acting potassium increased significantly,from 61mg/kg to 112mg/kg,an increase of 83.61%.According to the grading standard of the second soil census,the organic matter,effective phosphorus and fast-acting potassium contents of rice soils in Pingjiang County were at the medium,lacking and medium levels respectively during the second soil census period,and are currently at the rich,abundant and medium levels respectively,but according to the current grading standard of cultivated land quality monitoring,43.55%of the fast-acting potassium and 15.69%of the effective phosphorus contents of cultivated soils in Pingjiang County are still at the low level.(3)The current quality level of cultivated land in Pingjiang County is 4.81,mainly 3-7grades of land,the proportion of high-yield cultivated land is 27.98%,and the proportion of medium and low-yield cultivated land is 72.02%.The high-yield cultivated land is mainly distributed in the eastern and southern areas of Pingjiang County in Anding Town,Changshou Town,Gayi Town and Wushi Town in the northwest.Middle-yielding cultivated land is mainly distributed in Anding Town,Hongqiao Town,Gayi Town,Longmen Town,Meixian Town,Nanjiang Town,Sanshi Town,Sanyang Township,Wurnjiang Town,Wushi Town and Changshou Town.The main problem is that some of the cultivated land has low soil nutrient content,irrigation conditions are not fully guaranteed,and is prone to drought.Low-yielding cultivated land is mainly distributed in Wushi Town,Meixian Town,Changshou Town,Nanjiang Town,urnjiang Town and Anding Town,whose main problems are sticky soil texture,poor irrigation and drainage conditions and low soil nutrient content.