| Summary: | The interactions between nitrogen (N) and potassium (K) are important determinants of rice yield, but the mechanisms involved remain poorly understood. For example, N/K interactions may influence light utilization and N distribution in the canopy. Field experiments were therefore performed to resolve this issue, using factorial combination of N and K. The interaction between N and K had a significant effect on the grain yield, N uptake, and the NUE of grain production (NUEg), and biomass production (NUEb). The application of either N or K alone resulted in lower yields than the combined application of these nutrients. The combined application of N and K increased rice yields by 54.5% in 2018 and by 76.1% in 2019, compared with N0K0. Similarly, N uptake, NUEg, and NUEb were higher when N was supplied with K than with N application alone. The higher grain yields, N uptake rates, and NUEs observed with the combined N and K treatment were attributed to the following: (1) a higher leaf area index that resulted in better light interception; (2) improved the coordination of light and N distribution within the canopy. Evidence for improved light use by photosynthesis is provided by the observed lower light extinction coefficient (KL), the higher specific leaf N in the top leaves (SLNo), higher extinction coefficients for effective leaf N (KN) and KN/KL values. We conclude that the interactions between N and K support higher yields by improving canopy performance even at lower N rates. © 2021 The Authors. Food and Energy Security published by John Wiley & Sons Ltd.
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