Abstract:

 Farmland protection is the foundation of national food security and social stability In China，rapid industrialization and urbanization has catalyzed farmland resource deterioration To assure a stable supply of farmland，we need a comprehensive plan In a longterm food production plan，both quantity and quality of land are important Prime farmland，which is defined as highquality farmland in terms of fertility，location，and equipped irrigation system，is the most critical category of farmland as it can guarantee stable grain productivity Due to its important role in food production in China，prime farmland should be reserved for agricultural use and thus requires continual monitoring and defragmentation Conventional demarcation method of prime farmland planning，which has set a target in both quantity and quality of the farmland，often overlooks the productivity and location aspects，and thus has resulted in suboptimal efficiency This paper aims to explore new demarcation method of prime farmland based on productivity and spatial clustering To describe farmland quality，indexes for each land unit are constructed by three elements that consist of twelve factors These factors，according to their attributes，can be categorized into productivity and spatial diffusion type As each indicator has a value on a different scale，to eliminate the scale effect，the value of each indicator is normalized，based on which a comprehensive value is calculated for each land unit by weightadding models The comprehensive values of each unit are then used to describe the spatial differences of farmland quality in a region We use Kmeans spatial clustering method and landscape fragmentation measure in the defragmentation process The Kmeans spatial clustering method reduces fragmentation by accounting for both spatial proximity and attribute similarity of the land units The optimal number of land categories can be determined by the point where the marginal reduction in the fragmentation index is maximized as the number of categories varies Once the optimal category of farmland is found，the landscape fragmentation index can be calculated The value of this index changes depending on the minimum size of defragmented areas，the optimum of which corresponds to the largest marginal reduction in the fragmentation index We apply our demarcation method in Hefeng County，Hubei Province，China The resulting defragmented prime farmland in the county encompasses an area of 1617235 hm2 and the associated comprehensive quality indexes are all above 73 The fragmentation index is 126，which is significantly lower compared to the values obtained from the other two conventional methods This study can serve as a reference for future theoretical and empirical research on prime farmland