Sustainable Irrigation Management of Winter Wheat and Effects on Soil Gas Emissions (N 2 O and CH 4 ) and Enzymatic Activity in the Brazilian Savannah

Water scarcity and greenhouse gas (GHG) emissions pose significant challenges to sustainable wheat production in tropical regions such as the Brazilian Cerrado. This study evaluated the effects of different soil water depletion levels, denoted as f (20%, 40%, 60%, and 80% of available water capacity—AWC), on no-tillage winter wheat irrigated after rainfed soybean cultivation. Grain yield decreased significantly at depletion levels ≥ 60%, with the highest yields observed at f = 20% (6933 kg ha −1 ) and f = 40% (6814 kg ha −1 ). Water use efficiency (WUE) ranged from 12.4 to 14.0 kg ha −1 mm −1 , with no significant differences among treatments. Nitrous oxide (N 2 O) emissions peaked at f = 60% (4.55 kg ha −1 ), resulting in the highest average global warming potential (GWP = 1.185.78 kg CO 2 eq ha −1 ) and greenhouse gas intensity (GHGI = 192.66 kg CO 2 eq Mg −1 grain). Methane (CH 4 ) acted as a net sink across all irrigation levels. Soil enzymatic activities (β-glucosidase and arylsulfatase) were not significantly affected by irrigation management. Overall, irrigation scheduling based on f = 40% soil water depletion provided the best balance between productivity and environmental sustainability, representing a climate-smart and resource-efficient strategy for wheat production in tropical agroecosystems. These findings provide promising insights for tropical agriculture by showing that sustainable irrigation can balance productivity and climate mitigation in the Cerrado. Maintaining soil water depletion below 60% significantly reduces N 2 O emissions and environmental impact, emphasizing the importance of conservation practices. Additionally, preserving soil biological quality supports the long-term viability of these practices and offers valuable guidance for policies promoting efficient irrigation in climate-vulnerable regions.