2018 ASHS Annual Conference

Irrigation scheduling in fruit tree orchards requires measurements that are easy to translate into irrigation advice. Many growers in the Southeastern U.S. irrigate their trees only based on rainfall records, visual monitoring of tree and fruit growth, and estimating soil moisture with a hand squeeze test. Measuring soil tension with tensiometers is becoming more common since they are relatively affordable but, depending on the soil type, they may only indirectly reflect the tree water status. Tree-based water status indicators have been proven to be the best indicators for irrigation of tree orchards. However, drastic variation in daily environmental conditions, especially relative humidity and temperature, make difficult their application. The goal of this project is to improve the correlations and adjusted coefficients between soil and tree measurements to improve irrigation scheduling in fruit tree orchards. Tensiometers allowed the comparison of soil tension readings with dendrometers that measured the micro-variations in the tree trunks caused by movement of water. The maximum daily shrinkage (MDS) of the trunk diameter showed remarkably more variability under water deficit than the well-watered peach trees. Nevertheless, the daily fluctuating environmental conditions of South Carolina, especially relative humidity and temperature, seemed to be the main challenge to correlating values between the dendrometers to the tensiometers. Tensiometers deeper than 12” did not correlate to the tree based sensors at all. Humidity levels on days that were reading differently than expected were explored as well as when those humidity levels had a dramatic daily change compared to the MDS in stressed trees vs. non-stressed trees.