Evaluation And Analysis On The Quality Of Cultivated Land In The Main Corn Producing Area Of Jilin Province

Jilin Province is one of the main corn producing areas in China.The quality of cultivated land directly affects the national food security.In recent decades,the degradation of soil fertility caused by predatory use was obvious,especially in the subsurface layer.In this study,the corn cultivated soil in 6 urban areas of the main corn producing area of Jilin Province was taken as the research object,and a total of 320 soil samples were collected in the topsoil and subtopsoil.The main fertility factors,such as nitrogen,phosphorus,potassium,soil organic matter(SOM),soil p H and soil cation exchange capacity(CEC),which affect the quality of cultivated land were systematically studied.Descriptive statistics were made on the data of each index,and the distribution characteristics in each city were analyzed.The minimum data set method was used to determine the representative evaluation indicators,and the quality of cultivated land in the whole surface layer was evaluated.Based on Arc GIS,the spatial diagram of cultivated land quality indicators and the quality distribution map of cultivated land in the surface layer and subsurface layer were formed.The following conclusions are reached:(1)In the whole surface layer(0-40cm)of the main corn producing area,the sand content in Songyuan and the south of Tonghua was the highest.In the central black soil area,fine sand was the majority.The proportion of sand and clay was similar,and aggregate particles >0.25 mm accounted for 45% on average.(2)The soil organic matter content in the topsoil was stable,maintaining at about 26 g/kg in the past 20 years,which was at a medium level.Organic matter content in subsurface layer is about 25% lower than that in surface layer.(3)The soil acidification in the topsoil layer was serious,with the average value of 6.06.Except for the alkaline areas in Songyuan,nearly 50% of the cultivated land in Changchun,Siping,Jilin,Tonghua and Liaoyuan was still(weakly)acidic.In the past 10-20 years,the p H value of cultivated land in the 6 urban areas of Jilin Province decreased by 0.4-0.5 units on average.Subsurface tends to be neutral,the most suitable for crop growth.(4)Nitrogen and phosphorus were the highest among all nutrient factors,reaching the rich level.Jilin Province is a major corn planting province,and the application of a large amount of nitrogen and phosphorus fertilizer and corn straw returning measures increased the accumulation of soil carbon,nitrogen and phosphorus.Except Siping area,the total potassium content is extremely lacking,and the available potassium content is in the medium level.In the context of the national cultivated land,the phenomenon of potassium deficiency is also particularly prominent.Nearly 56% of cultivated land lacks potassium.Although it is restricted by the content of soil potassium(non-mineral)and the conversion rate,the potassium loss caused by improper fertilization,irrigation,tillage and other reasons should be the focus of attention.(5)Cultivated land quality was well evaluated through the cultivated land quality evaluation system established by MDS.Sand grain,total phosphorus,CEC and total potassium were determined by soil index MDS.Sand,available phosphorus,available potassium,total nitrogen,p H were determined in the subsoil layer.The reasonableness verification of all indexes SQI values of surface layer and subsurface layer shows that the R2 of the established linear regression equation is 0.732 and 0.746,respectively,with p <0.001.The quality of cultivated land in the subsurface layer is not much different from that in the surface layer,and the quality of cultivated land in the surface layer is about 5%-10% higher than that in the surface layer.