Evaluation of rice planting suitability using GIS and geochemical land quality data-A case study of Qingyang County, Anhui Province

In order to accelerate the construction of high-standard basic farmlands in Qingyang County, Anhui Province and to conduct more accurate evaluation of rice planting suitability, an Analytic Hierarchy Process (AHP) was used to evaluate the suitability of rice planting with site conditions, soil physicochemical properties, soil quality and land management as the criterion layer. We then used the driving factors as the index layer to successively devise a three-level hierarchical model for the evaluation. Thus, the evaluation system comprising 12 indicators (including soil nutrient, soil environment, soil texture, soil organic matter, drainage capability, irrigation capacity, and etc.) were constructed based on geochemical land quality data of the prime farmland in the study area and on the demand for local rice production. With the polygons of the Second Land Survey as evaluation units, the field slope was obtained from digital elevation model (DEM) data, and combined with spatial analysis technology in GIS to simulate spatial interpolation of geochemical data. The Delphi method was used to determine index membership and build judgment matrix to calculate the weight of each index in order to obtain the comprehensive rice planting suitability index (RSI). The results showed that the "highly suitable" land area was 36.89 km², accounting for 19.80% of the total area, which was mainly distributed in the central and southern regions of the study area. The areas of "suitable" and "barely suitable" lands were respectively 61.95 km² (33.25%) and 60.89 km² (32.68%) and were sporadically distributed. The area of "unsuitable" land was 26.60 km² (14.27%) and was also mainly distributed in the central and northern regions of the study area. The measured cadmium content of rice seeds and RSI were significantly negatively correlated. The cadmium content of rice grains gradually decreased with the increasing of RSI. The low heavy metal content implied improvement of rice quality and reduction in potential damage to the ecological environment through food chain. The results proved the correctness and applicability of the evaluation method from the perspective of ecological security. We explored rice production issues reflected by geochemical data of land quality. The established evaluation method of agricultural planting suitability improved the past evaluation methods, which was subjective and non-suitable for application due to many descriptive indicators and uncertain indicator grading.