Evaluation of the quality of soil fertility using entire-array-polygon indicator method

Soil is extremely important for plant growth and land productivity. A good understanding of the soil fertility quality is helpful to clearly learn soil environment condition, and it also contributes to effectively and rationally use of land resources. Currently, there are many methods evaluating soil fertility quality and assessing the condition of soil environment. However, due to subjective experience influencing on indicator weight decision, the results of these evaluation methods are more or less deviation from actual situation. And the results are usually not visualized. In this study, a new method — entire-array-polygon graphical representation and indicator method, a method used in eco-city evaluation, was used to evaluate soil fertility quality. The feasibility of the entire-array-polygon indicator method was also verified. A black soil in Jilin Province was used to establish both the evaluation indicator system and classification standard from three aspects — soil nutrient, soil structure and soil environment. The study evaluated a representative test data taken from 13 field sampling points in black soil fields in Jilin Province. The evaluation results of the entire-array-polygon indicator method were compared with the results of extenic method and improved artificial neural network method. The results clearly showed that soil fertility quality at the 13 sampling points in the study area was level III and the soil quality belonged to moderate grade. The study also advanced soil improvement measures based on the limiting factors of different sampling points. Sampling points G3, G7 and G8 needed more phosphor fertilizer, points G4, G10 and G14 needed more attention in terms of cropping systems and improvement of soil structure. The results of comparison with other evaluation methods indicated that the entire-array-polygon method was feasible for evaluating soil fertility quality. The evaluation results were highly consistent with those of other methods, with different evaluation results for only 1 to 3 sampling points. The entire-array-polygon indicator method was visual and easy to understand and convenient to quantify in terms of programming evaluation factors and avoiding subjective and arbitrary. It proved to be a new and useful method for evaluating soil fertility quality and provided a reference for application in other regions or soil types for assessing soil fertility quality.