5
g/kg
200
g water per g biomass
5
g/kg
200
g water per g biomass
The Water Use Efficiency (WUE) Calculator determines how efficiently a plant converts water into biomass. WUE is defined as the ratio of biomass produced to water consumed (transpired), and it is a critical metric in agriculture, ecology, and water resource management. Plants with higher WUE produce more dry matter per unit of water, which is increasingly important in regions facing water scarcity and under climate change scenarios.
Enter the total biomass produced (in grams of dry weight) and the total water transpired (in kilograms) over the same period to obtain WUE and its inverse, the water requirement.
The calculator computes two complementary metrics:
WUE can be measured at different scales: whole-plant (gravimetric), leaf-level (instantaneous gas exchange), or ecosystem (eddy covariance). At the leaf level, intrinsic WUE is the ratio of net photosynthesis to stomatal conductance. This calculator uses the whole-plant gravimetric approach, which is the most common for pot experiments and field trials.
Inputs
Results
Wheat producing 50 g of biomass while using 10 kg of water has a WUE of 5 g/kg, meaning 200 g of water per gram of biomass.
Inputs
Results
Maize produces 80 g from the same 10 kg of water, yielding a higher WUE of 8 g/kg, typical of C4 plants.
C4 plants (maize, sorghum, sugarcane) have a CO₂-concentrating mechanism that allows them to fix carbon more efficiently at lower stomatal conductance. This means their stomata can be partially closed, reducing water loss while maintaining high photosynthesis rates. Typical WUE values are 4-6 g/kg for C3 crops and 7-12 g/kg for C4 crops. CAM plants (cacti) have the highest WUE because they open stomata only at night.
At the whole-plant level, WUE is measured by growing plants in sealed pots where water inputs are precisely controlled and transpiration is calculated from water balance. At the leaf level, a portable gas exchange system simultaneously measures CO₂ uptake and water vapor loss. At the ecosystem level, eddy covariance towers measure CO₂ and water fluxes above the canopy.
With increasing water scarcity and competition for freshwater resources, improving crop WUE is essential for sustainable agriculture. Breeding for higher WUE, optimizing irrigation schedules, and selecting drought-adapted varieties can significantly reduce agricultural water consumption while maintaining or improving yields. This is especially critical in arid and semi-arid regions where water limits crop production.
Roboculator Team
The Roboculator Team explains calculations, planning tools, and practical formulas in clear language for real-life situations.
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