Changes in rainfall and temperature regimes increasingly threaten global crop productivity, particularly in water‐limited regions. Climate‐smart agriculture aims to improve yields while minimizing its climate impact, such as from soil greenhouse gas (GHG) emissions driven by microbial activity. From an irrigation perspective, this underscores the need to assess irrigation practices beyond the traditional objectives of maximizing yield and water use efficiency by also considering their climate impact from soil GHG emissions. To address this gap, we frame climate‐smart irrigation as a multi‐objective optimization problem and derive a dual‐index framework for evaluating irrigation practices across productivity, water consumption, and climate impact dimensions. The Marginal Irrigation Water Productivity (MIWP) index quantifies additional yield per unit of irrigation water, while the Marginal Irrigation Climate Impact (MICI) index measures the associated changes in soil GHG emissions. We apply this dual‐index framework to wheat and rice field irrigation studies with varying soil GHG compositions, showing its ability to assess irrigation across different crop systems. Crop model simulations further demonstrate how different irrigation practices are mapped within the MIWP‐MICI space, where Pareto‐optimal solutions highlight trade‐offs between productivity and climate impact goals. Our approach provides a consistent, quantitative basis for comparing irrigation across multiple dimensions of climate‐smart irrigation.
