Current situation of the main crop straw nutrient resources and the substitute potential of crop straw for chemical fertilizer:A case study of Anhui Province

Anhui Province is rich in crop straw resources, it is important to fully utilize straw nutrient resources for the purpose of maintaining a nutrient balance in farmlands. For this cause, the potential of straw as a natural alternative to chemical fertilizers was evaluated in order to provide a scientific basis for the reduced use of chemical fertilizers in Anhui Province. In this study, we selected main crops such as rice, wheat, corn, soybean, peanut, and rape as study subjects in Anhui Province. We consulted the published literature and statistical data, and estimated the amount of straw, straw return rate, and nutrient utilization rate of main crops in Anhui Province in 2017. The results showed that the amount of straw estimated at 46.999 million tons in 2017. Furthermore, the distribution of straw resources was more in the northern and the middle regions of the province, and less in the southern regions. We also found that the total amount of straw nutrient resources was 1.248 million tons. The amounts of N, P₂O₅, and K₂O were 0.381, 0.114, and 0.753 million tons, respectively, and these accounted for 40.1%, 32.1%, and 68.9% of the main crop nutrient requirements of the entire province. Therefore, the potential of straw replacing chemical fertilizers is great in theory when all the straw is returned to the soil and the nutrients in the straw are fully utilized. However, the utilization rates of N, P₂O₅, and K₂O were only 38.9%, 52.3%, and 69.9%, respectively. The actual nutrients contents of N, P₂O₅, and K₂O of crop straws returned to the field accounted for only 15.6%, 16.8%, and 48.2%, respectively, of the nutrient demands of the main crops. Moreover, the actual amounts of N, P₂O₅, and K₂O returned to the field accounted for 8.6%, 6.4%, and 41.4% of the total input, respectively. By returning straw to the farmland, approximately 0.633 million tons of chemical fertilizer can be saved, representing 19.8% of the amount of chemical fertilizer that would have been used without the straw. It is also worth noting that the application reduction rates of N, P₂O₅, and K₂O were 11.4%, 17.2%, and 40.7%, respectively. Thus, the improvement in straw returning-to-field rate and release rate of nutrients in crop growth period point towards the benefits of promoting the reduced use of chemical fertilizers.