Sustainable potassium (K) management at different soil sites requires understanding the relationships between crop productivity and long-term K fertilizations on a regional or national scale.We analyzed responses of grain yield of wheat (Triticum aestivum L.) and maize (Zea mays L.),K efficiency,and partial balance (difference between K input through fertilizer and K output in the aboveground biomass) during 15-(1990-2005) or 18-year (1990-2008) K fertilizations at five distinctive agroecological zones across China.Compared to the inorganic nitrogen (N) and phosphorus (P) fertilization,the inorganic NPK fertilization significantly increased grain yields of wheat (21%) and maize (16%-72%) at Qiyang and Changping,where soils have low exchangeable and non-exchangeable K contents,but not at rmqi,Yangling and Zhengzhou,where soils have a high exchangeable and non-exchangeable K and/or low N/K ratio in crop plants.Compared to the inorganic NPK fertilization,the inorganic NPK (30% N) and organic manure (70% N) fertilization (NPKM) increased grain yields of wheat (14%-40%) and maize (9%-61%) at four sites,but not at Zhengzhou.For a productivity of wheat at 2-5 t ha-1 or maize at 3-6 t ha-1,13-26 or 9-17 kg K ha-1 were required to produce 1.0 t wheat or maize.The NP fertilization resulted in the lowest negative partial K balance and accumulated 52 kg K ha-1 year-1 less than the NPK fertilization,which accumulated 28 kg ha-1 year-1 less K than the NPKM fertilization.A re-evaluation of the site-specific fertilization effects on N/K ratio in crop plants and soil K accumulation under current NPK and NPKM fertilization is urgently needed to increase both crop yield and K use efficiency at different agroecological zones across China. Sustainable potassium (K) management at different soil sites requires understanding the relationships between crop productivity and long-term K fertilizations on a regional or national scale. We analyzed responses of grain yield of wheat (Triticum aestivum L.) and maize (Zea mays L . K Efficiency, and partial balance (difference between K input through fertilizer and K output in the aboveground biomass) during 15- (1990-2005) or 18-year (1990-2008) K fertilizations at five distinctive agroecological zones across China .Compared to the inorganic nitrogen (N) and phosphorus (P) fertilization, the inorganic NPK fertilization significantly increased grain yields of wheat (21%) and maize (16% -72%) at Qiyang and Changping, where soils have low exchangeable and non-exchangeable K contents, but not at  rmqi, Yangling and Zhengzhou, where soils have a high exchangeable and non-exchangeable K and / or low N / K ratio in crop plants. Compared to the inorganic NPK fertilization, the inorganic NPK (30% N) an Wheat grain (14% -40%) and maize (9% -61%) at four sites, but not at Zhengzhou. For a productivity of wheat at 2- 5 t ha-1 or maize at 3-6 t ha-1, 13-26 or 9-17 kg K ha-1 were required to produce 1.0 t wheat or maize. The NP fertilization resulted in the lowest negative partial K balance and accumulated 52 kg K ha-1 year-1 less than the NPK fertilization, which accumulated 28 kg ha-1 year-1 less K than the NPKM fertilization. A re-evaluation of the site-specific fertilization effects on N / K ratio in crop plants and soil K accumulation under current NPK and NPKM fertilization is urgently needed to increase both crop yield and K use efficiency at different agroecological zones across China.