Study on the input and demand of crop nutrients and the potential of fertilizer reduction in Anhui Province

The use of organic-inorganic integrated farmland nutrient management model is an effective approach to develop sustainable agriculture in China. As nutrient demand and supply in agricultural production in various regions are undefined, it is crucial to study the relationships among organic fertilizer nutrient resources, fertilizer nutrient input, and crop nutrient demand to promote the rational distribution and application of nutrient resources. By using previously published methods and statistical analysis, here, we evaluated the nutrient composition of organic fertilizers (including straw, manure, green manure, and cake fertilizer). We aimed to clarify the current situation of organic and inorganic nutrient inputs for agricultural production in 16 cities in Anhui Province from 2010 to 2016, and evaluate differences and relationships among organic and inorganic nutrients and crop nutrient demand according to the local structure of agricultural planting. Finally, we explored the potential for fertilizer reduction in Anhui Province. The annual average amount of organic fertilizer in Anhui Province from 2010 to 2016 was 2.877 million tons, and that of N, P₂O₅, and K₂O was 1.044 9, 0.396 0, and 1.436 1 million tons, respectively, which could meet the nutrient demand for crops. However, the utilization rate of N, P₂O₅, and K₂O in organic fertilizer in the current season was as low as 21.44%, 19.91%, and 52.61%, respectively. Therefore, the actual return amount of organic fertilizer only accounted for 20.74% (N), 25.38% (P₂O₅), and 63.61% (K₂O) of the crop nutrient demand, and only 11.87% (N), 10.27% (P₂O₅), and 51.35% (K₂O) of the total nutrient input of farmland. The actual nutrient input (including organic fertilizer and chemical fertilizer) in the province was 1.75 (N), 2.47 (P₂O₅), and 1.24 (K₂O) times of the crop nutrient demand. The application of N in seven cities and the application of P₂O₅ in 13 cities were more than two times of the crop demand; there was a high risk of environmental pollution in these cities. By controlling the nutrient input, the reduction potential of fertilizer in Anhui Province was 35.12%, and that of N, P₂O₅, and K₂O was 21.28%, 23.97%, and 78.61%, respectively. By improving the utilization rate of organic fertilizer and developing winter green fertilizer, Anhui Province can achieve the maximum reduction in fertilizer application. This study provides reference data for zero growth of fertilizer and green sustainable development of agriculture and animal husbandry in Anhui Province.