Monitoring Stem Water Potential with an Embedded Microtensiometer to Inform Irrigation Scheduling in Fruit Crops

Abstract

The water status of fruit and nut crops is critical to the high productivity, quality and value of these crops. Water status is often estimated and managed with indirect measurements of soil moisture and models of evapotranspiration. However, cultivated trees and vines have characteristics and associated cultural practices that complicate such methods, particularly variable discontinuous canopies, and extensive but low-density, variable root systems with relatively high hydraulic resistance. Direct and continuous measurement of plant water status is desirable in these crops as the plant integrates its unique combination of weather, soil and cultural factors. To measure plant water potential with high temporal sampling rates, a stem-embedded microchip microtensiometer sensor has been developed and tested in several fruit crops for long-term continuous monitoring of stem water potential. Results on several fruit crops in orchards and vineyards have been good to excellent, with very good correlations to the pressure chamber standard method. The primary challenge has been establishing and maintaining the intimate contact with the xylem for long periods of time, with variable stem anatomies, stem growth and wound reactions. Sources of variability in the measurements and utilization of the continuous data stream, in relation to irrigation scheduling, are discussed. Direct continuous and long-term field measurements are possible and provide unique opportunities for both research and farming.

Estimation of Water Potential in Corn Plants Using Machine Learning Techniques with UAV Imagery and Evaluating the Effect of Flying Height

“…In the present study, flights were conducted at lower altitudes (30 to 70 m) to capture the finer details of individual leaves. The R 2 values obtained in the present study are consistent with the general trend found in other studies, which typically report R 2 values of no more than 0.7 when correlating images with water potential [12]. The present study also addressed the temporal factor by conducting multiple measurements throughout the crop cycle.…”

Relating microtensiometer-based trunk water potential with sap flow, canopy temperature, and trunk and fruit diameter variations for irrigated ‘Honeycrisp’ apple

“…Trunk water potential (Y trunk ) measured using microtensiometers has been recently reported as a reliable indicator of tree water status in apples (Lakso et al, 2022). This indicator was strongly related to the stem water potential measured with the pressure chamber, the reference indicator for assessing the water status of fruit trees (McCutchan and Shackel, 1992;Naor, 2000;Shackel, 2011).…”

“…Microtensiometers consist of microelectromechanical pressure sensors that are embedded into the trunk (Pagay et al, 2014) and measure trunk water potential. Their measurements have been recently validated in different fruit trees and vines and under different environmental conditions and irrigation regimes with promising results (Blanco and Kalcsits, 2021;Lakso et al, 2022;Pagay, 2022;Conesa et al, 2023;Gonzalez Nieto et al, 2023a). Its continuous data acquisition may provide reliable and robust water status indicators that correspond well to commonly measured plant response traits such as the sap flow rates, the temperature of the canopy or the daily variations of the trunk and fruit diameter.…”

Technologies and Innovative Methods for Precision Viticulture: A Comprehensive Review

“…Hyperspectral reflectance data is usually collected using an instrument named spectrometer. Measurements with the spectrometer are carried out at specific times of the day to reduce variations in the solar zenith angle, and a radiometric calibration must also be carried out using a white standard panel (spectralon) (Figure 5a) [133]. Through radiometric calibration, the image values recorded by the sensor and expressed in DN, are converted into reflectance values or radiance (Figure 5b).…”