Peach Water Use
The lysimeter at Kearney has been used to measure peach water use. It is essentially a large planter box on top of a sensitive truck scale. It can accurately measure the hourly loss of water by soil evaportation and tree transpiration (evapotranspiration or ETc). Built in 1986, it (and the surrounding 3 acres) was planted to O'Henry (late July variety) peach trees from 1988 until 1996. Then, from 1999 until 2006, Crimson Lady (late May variety) peaches were grown in the lysimeter and surrounding field. The lysimeter has been used to generate daily and seasonal crop coefficients (Kc) by dividing daily ETc values with reference crop evapotranspiration (ETo) values derived from a nearby weather station. The general seasonal Kc pattern is shown in a Cal Ag article and a more detailed scientific analysis (2003 Irrig Sci - Peach Crop Coefficients) has also been published. Click here to see each year's seasonal pattern of crop coefficients.
The lysimeter has also been very useful for examining several different relationships. First, we used it for studying water stress and evaluating simpler measurements that might correlate with water use such as trunk sap flow and stem water potential (ref 1; ref 2). Second, we found a good correlation between canopy light interception and tree water use (Light Interception & Crop Coeff). Third, by covering the lysimeter surface occasionally we were able to separate out soil evaporation from tree transpiration (same ref). Finally, we used all this information to develop a model for estimating water use in a peach orchard (Modeling Peach ET - 1; Modeling Peach ET - 2).