Assessing water stress in a high-density apple orchard using trunk circumference variation, sap flow index and stem water potential

• DOI: 10.3389/fpls.2023.1214429
• Publication Date: 2023-08-03T14:05:59Z
• Authors: William D. Wheeler; Brent Black; Bruce Bugbee
• Keywords: Circumference; Orchard; Water Stress

Introduction Automated plant-based measurements of water stress have the potential to advance precision irrigation in orchard crops. Previous studies shown correlations between sap flow, line variable differential transform (LVDT) dendrometers and fruit tree drought response. Here we report season-long automated measurement maximum daily change trunk diameter using band heated needles measure a simplified flow index (SFI). Methods Measurements were made on two apple cultivars that stressed at 7 12 day intervals by withholding until average stem (Ψ Stem ) dropped below -1.5 MPa, after which was restored cycle repeated. Results Dendrometer shrinkage (MDS) highly correlated (r² = 0.85) with pressure chamber potential. The SFI less but evaporative demand 0.82) as determined Penman-Monteith equation (ET r ). Discussion high correlation ET suggests high-density orchards resemble continuous surface, unlike widely spaced trees. MDS Ψ higher during early season than late growth. Band are labor intensive install LVDT non-invasive so well suited commercialization.