Current potassium-management status and grain-yield response of Chinese maize to potassium application

The great achievement of the development of intensive in agriculture in China can be partly attributed to substantial increases in mineral-nutrient application. However, whereas farmers tend to apply high levels of nitrogen (N) and phosphorus (P) application of potassium (K) has been neglected. A greater understanding of the relationship between maize (Zea mays L.) grain yield and K-application rate is thus required to provide an improved rationale for K fertilization for farmers in the various agro-ecological regions of China. In this study, a total of 2765 farmers' survey data and 3124 on-farm experiments across major maize agro-ecological regions in China were collected and evaluated for farmers' K-management status and to determine grain-yield response to K application. Nationally, the average K-application rate on farms was 26kg K ha1 and varied from 0 to 158kg K ha1, with a coefficient of variation of 107%, but the applied K-fertilizer rates were not related to grain yield. Maize grain yields at recommended K rates increased by 14.0%, 14.7%, 19.4%, and 4.3% in Northeast China, North China Plain, Southwest China, and Northwest China, respectively, compared to zero K fertilization (K0). Increased yield due to K fertilization (IYmax, difference between maximum yield across all treatments and K0-treatment yield for each experiment) averaged 1.4 t ha1 but varied widely in different agro-ecological regions. Soil extractable K (NH4OAc-K) and intercounty variation resulted in large variation in IYmax in agro-ecological regions, as did other factors, such as use of particular maize hybrids, soil types, or years in different regions.