Measuring crop water use for precision irrigation

The water use of the irrigated production sector in southern Alberta is constrained by the finite volume of water that is present in rivers, lakes, and reservoirs in the region. In order to continue growing a diverse selection of crops, expand high-value cropping areas, and adapt to climate change within the boundaries of Alberta's water licensing system, irrigation farmers try to ensure that the majority of their irrigation applications is used by plants and not lost to the atmosphere or deeper soil layers. This requires measurements of the volume of water available in the soil, the volume of water applied via irrigation or rainfall, and the amount of water transpired by a field crop. Unfortunately, the latter is difficult to measure and in the majority of practical studies, a maximum potential crop water use rate is calculated instead from weather conditions and crop characteristics. However, due to the variability of water available for uptake by plants, the actual crop water use may be quite different from the potential. This introduces uncertainties in the determination of irrigation water use efficiency. With the purchase of an Eddy Covariance system, Lethbridge College will be able to measure actual crop water use rates in irrigation research projects. These measurements will help us develop precision irrigation management strategies and identify measures that increase irrigation water use efficiency.