Evaluation and Classification of Nationwide Arable Land Quality in China.

Abstract: The first program of evaluation and classification of arable Land Quality (ECALG)  in China was initiated in 2009. Cultivated lands were categorized to 15 levels. The farmlands classified as the first level have the greatest productivity while farmlands at 15th level have the lowest productivity. The preliminary results of classification across the nation were released in 1999.  The classification of farmland was updated again in 2014. The purpose of this study is to introduce the land classification method. The method consists of productivity evaluation methods of Agricultural Ecological Zone (AEZ) of Food Agriculture Organization (FAO) and a crop growth model. First, the climate productivity (CP) of different cropping systems was  calculated in terms of temperature, rainfall and solar radiation in each ecological zone across the nation. Second,  soil coefficient associated with organic matter, soil texture and soil depth, land use coefficient related to availability of irrigation and accessibility of transportation, and economic cost-return coefficient were obtained by field investigation and social-economic survey. Third, land productivity is classified to three categories via CP multiply by soil coefficient, land use coefficient and economic coefficient, respectively.  As a result, land productivity was classified from 1 to 15 levels.

The results of classification in 2014 revealed that the total area of arable land was approximately 1.4×10⁸ hm² in China. Only 2.9% of total arable land was classified as 1-4 level, 26.5% of total arable land was at level 5-8, 52.9% of total arable land was at level of 9-12, and 17.7% of total arable land at level 13-15. In general, the area weighted average level is 9.96 and the acreage of level less than the average value accounted for 60.2%. It indicates that the productivity per unit arable land is extremely low. ECALG combined use top-down  and bottom-up method. On the one hand, according to top-down method, from national scale- ecological zoning scale-provincial scale, the CP was calculated for 12 ecological zones and 41 sub-ecological zones which can be used for every province of China. On the other hand, based on  bottom-up method, the investigation and evaluation results of field plot, village, town and county can be summarized step by step from bottom to top until generate the provincial and national results. The method including country - province - county - town, village - plot multiple evaluation scale, using 1:10 000 large scale, reflects the characteristics of high precision and the summarizing results is nationally comparing through a standard grain transfer coefficient designing. ECALG help China to establish a nationally unified and comparing system of arable land quality and it is of great significance for the service of food security and arable land quality management.

Key words: Agricultural Ecological Zone , crop growth model, land productivity; arable land; evaluation; classification;  nationally unified and comparing level; China