Research On Suitability And Remediation Technology Of Dry Land Into Paddy Field In Hilly And Mountainous Areas

With the continuous improvement of the level of new urbanization,a large amount of high-quality arable land has been occupied,and the contradiction between man and land has become more acute.Since the 18th National Congress of the Communist Party of China,the central government has attached great importance to the protection of arable land and proposed to strictly observe the red line of 1.8 billion acres of arable land and strictly implement the arable land occupation-compensation balance system of"predominantly supplementing the quality,occupying paddy fields and supplementing paddy fields".Chongqing is located in the hilly and mountainous areas of the southwest.The special topography and landforms have broken the arable land.The reserve resources of arable land are scarce,and the quality of arable land needs to be improved.In order to better carry out arable land protection,strictly implement the arable land occupancy and compensation balance system,improve the quality of arable land,and carry out the suitability evaluation and improvement technology research of the dry land into paddy field has important practical significance and practical value.Dry land into paddy field refers to the process of transforming conditional dry land into paddy field through land consolidation projects,and is the main manifestation of the structural adjustment of regional agriculture.In order to understand the necessity of dry land into paddy field,the suitability of construction,and to explore the remediation technology of dry land into paddy field,this article takes Wanzhou District in hilly and mountainous areas as an example,based on the four phases of land use images in Wanzhou District in 1990,2000,2010 and 2020,using land use change dynamics,land use transfer matrix,nuclear density estimation and landscape index models and other methods by using Arc GIS and FRAGSTATS software to analyze the spatio-temporal characteristics of the arable land in Wanzhou District.The construction layout follows the principle of selecting evaluation factors from the topography,soil,irrigation and drainage,location and nature of arable land,etc.,to construct an evaluation index system for the construction suitability and spatial stability of dry land into paddy field,and the analytic hierarchy process is used to determine each evaluation The weight of the factors,using Arc GIS to analyze the construction suitability and spatial stability of the dry land into paddy field in Wanzhou District,and use the coupling and coordination of the two to reveal the difficulty of dry land into paddy field construction.On this basis,through spatial autocorrelation analysis,the spatial agglomeration of the coupling coordination degree of dry land into paddy field construction is explored,and a scientific basis is provided for the delimitation of the dry land into paddy field construction area and the site selection of the project area.Take the project of dry land into paddy field in 2 villages such as Hongxing,Xiongjia Town,Wanzhou District,as an example to clarify the remediation technology.Research indicates:(1)The area of arable land in Wanzhou District has been declining from 1990 to 2020.The area of arable land decreased by 10,912.59 hm~2 in 30 years,and the dynamic degree of arable land utilization was-0.2%.In the past 30 years,the arable land in Wanzhou District has mainly changed to construction land,forest land and water areas;the area of arable land distribution in 1990-2020has changed from 5 to 4 significant core distribution zones;the landscape pattern index shows that in the past 30 years The arable land landscape in Wanzhou District is showing a trend of fragmentation.As the area of arable land continues to decrease,the fragmentation of the arable land landscape has further expanded.From the perspective of food security and ecological protection,in the future industrial restructuring and high-standard farmland construction,a certain amount and quality of arable land must be stabilized.At the same time,it is necessary to strengthen the application of dry land into paddy field technology and promote the implementation of it’s project.(2)There are obvious regional differences in the construction suitability of the dry land into paddy field in Wanzhou District.Among them,the subdistricts,Tiancheng Town and Dazhou Town have good suitability for the construction of cultivated land,while the low suitability areas are obviously affected by the mountain and hilly terrain.Areas with low spatial stability are mainly distributed in towns such as Danzi Town and Houshan Town.The cultivated land plots of these townships are far away from the town and the water source,and most of them are not basic farmland and have poor stability.Through the calculation of the coupling coordination degree and the classification of levels,the difficulty of the construction of dry land into paddy field in Wanzhou is divided into 4 levels.Among them,the areas of easy-to-renovate and key-reconstructed plots are1817.02 and 14680.40 hm~2,respectively,and the areas of difficult-to-reform and unsuitable plots are43461.13 and 30319.27 hm~2.The spatial autocorrelation analysis of the coupling coordination degree of dry land into paddy field project identified five areas,namely,significant HH area,significant HL area,non-significant area,significant LH area,and significant LL area of the dry land into paddy field project,and finally determined the dry land into paddy field in Wanzhou District.The construction areas of dry land into paddy field are mainly distributed in Yujia Town,Changtan Town and all streets under the jurisdiction of the district.(3)Taking the dry land into paddy field project in Hongxing and other(2)villages in Xiongjia Town,Wanzhou District as an example,the comprehensive soil condition,water source situation and villagers’wishes were comprehensively selected to implement the dry land into paddy field project through field surveys in the project area.There are 12 pieces of dry land with an area of 7.79 hm~2.Among them,the thickness of topsoil stripping is generally 20-25 cm,and the aspect ratio of the field should generally be controlled at 4:1-10:1;the thickness of the field seepage prevention should not be less than 10 cm.After the anti-seepage project is completed,it should be immediately cover the stripped farming layer soil,level it and flood the field.The height difference of the newly added paddy field should be controlled within±3 cm,the gravel content should be≤1%,and the terraced rate of the paddy field should be≥70%.Layer thickness≥20 cm,effective soil layer thickness≥50cm,suitable for small,micro-machine farming rate≥70%.The design standard of drainage ditch adopts rainstorm lasting 1-3 d,and 3-4 d can be drained to the depth of the crop tolerant water.The irrigation guarantee rate is 75%,the irrigation water utilization coefficient is≥0.65,and the flood control standard is once every 10 years.The field road network density is≥16 m/hm~2,and the specification is 3.0-4.0 m wide;the production road network density is≥30 m/hm~2,and the specification is 0.8-2.5 m wide.