Characteristics of middle-season rice yield, fertilizer increase yield effect and use efficiency in the Yangtze Valley

Objective This study was designed to examine irrational fertilization in rice production regions in the Yangtze Valley. Rice yield response to nitrogen (N), phosphorus (P) and potassium (K) fertilizer application and fertilizer use efficiency under optimized fertilization conditions were summarized. Our study provides a scientific basis for regulating fertilizer allocation, optimizing the application, and promoting effective production.

Methods The data in this article were derived from the field experiments conducted by the International Plant Nutrition Institute in the Yangtze Valley from 2000 to 2017 and published papers on rice field trials. The latter was obtained by searching field or combination of fields (rice, rice + yield and rice+ fertilizer utilization rate) in the CNKI database, giving 2165 field trials. The experimental treatments include optimal fertilization, farmers' practices, and N, P or K omission treatments. These treatments were intended to explore the characteristics of potential rice yield, relative yield, agronomic efficiency and partial factor productivity in the Yangtze Valley provinces (cities) (Sichuan, Yunnan, Guizhou, Chongqing, Hubei, Anhui, Jiangsu, Zhejiang, and Shanghai).

Results The average yield of middle-season rice in the Yangtze Valley under optimal fertilization treatment was 9.3 t/hm². Anhui Province had the highest average yield (10.1 t/hm²), and Hubei Province recorded the lowest average yield of 8.7 t/hm². The average yield response and relative yield of N, P and K fertilizer application were 2.1, 0.8 and 0.9 t/hm², and 0.76, 0.91, and 0.90, respectively. Under the optimal fertilization treatment, the average agronomic efficiency and partial factor productivity of N, P and K fertilizers were 11.3, 11.3, and 9.2 kg/kg, and 49.8, 126.7, and 92.9 kg/kg, respectively. Compared to farmers' fertilization practices, optimal fertilization increased the average yield by 0.7 t/hm², accounting for 8.3% of farmers practices. The agronomic efficiency of N, P and K fertilizers increased by 4.5, 5.0, and 3.4 kg/kg, respectively, and the partial factor productivity of N fertilizer application increased by 10.0 g/kg.

Conclusions Optimal fertilization effectively increased the yield and fertilizer use efficiency of middle-season rice in the Yangtze Valley. The contribution of N, P and K fertilizers to rice yield in the Yangtze Valley reached 24%, 9%, and 10%, respectively. However, there are differences among provinces (cities) and significant variation within the province. The rice yield is closely related to the balanced application of fertilizers. However, there was excessive N fertilizer application and insufficient K fertilizer application in the rice production of the Yangtze Valley. Optimizing nutrient management strategies is of great significance to improve rice yield and fertilizer use efficiency in this region.