A Stem Water Potential Model Based on Evapotranspiration and Soil Type.

Abdelmoneim (Moneim) Mohamed, UCCE Advisor in Modesto

Almond (Prunus dulcis) is currently grown on over 1 million acres in California. The recurring droughts in California coupled with the need to comply with the Sustainable Groundwater Management Act (SGMA) are expected to reduce the amount of water available for almond production. Improved water use efficiency of almond production can be achieved through site-specific irrigation scheduling based on stem water potential (SWP), soil type, and percent evapotranspiration. SWP measurement typically occurs at midday using a pressure chamber which is considered the most accurate tool for plant water status. Although SWP is driven by air temperature and relative humidity, it can be largely affected by deficit irrigation and soil texture. Measuring SWP in the field with a pressure chamber is laborious, and therefore, not widely adopted within the almond industry. Thus, the main objective of this work is to create a user-friendly, SWP model based on percent ET (regulated deficit irrigation) and soil types. Ultimately this model will allow growers to estimate SWP based on local weather conditions coupled with information on soil type and irrigation history in lieu of using a pressure chamber.  It will provide for site-specific irrigation scheduling, that is user-friendly, likely increasing grower use of more precise irrigation strategies. The model, in turn, will lead to more judicious use of available water, and maximum profitability for growers. Additionally, the model benefits include complying with state regulations.  Results from this project will be disseminated to almond growers and industry professionals using field days, extension publications, electronic and online media, and journal articles.