Harvesting Method Affects Water Dynamics and Yield of Sweet Orange with Huanglongbing

Changes in grove management practices may change crop water dynamics. The objective of this study was to estimate sap flow, stem water potential (Ψ stem ), and citrus yield as affected by harvesting methods in sweet orange ( Citrus sinensis ) trees affected by Huanglongbing. The study was initiated in March 2015 for two years on five-year-old commercial sweet orange trees at a commercial grove located at Felda, Florida (26.61° N, 81.48° W) on Felda fine sand soil (Loamy, siliceous, superactive, hyperthermic Arenic Endoaqualfs). All measurements were replicated before and after harvest in four experiments (A, B, C and D) under hand and mechanical harvesting treatments. Sap flow measurements were taken on four trees per treatment with two sensors per tree. Sap flow measured by the heat balance method at hourly intervals during March and April of 2015 and 2016 significantly declined after harvesting by 25% and 35% after hand and mechanical harvesting, respectively. Ψ stem measured after harvest was significantly higher than measurements before harvest. The average value of Ψ stem measured increased by 10% and 6% after hand and mechanical harvesting, respectively. Mechanical harvesting exhibited lower fruit yields that averaged between 83%, 63%, 49% and 36% of hand-harvested trees under A, B, C and D experiments, respectively. It is concluded that the hand harvesting method is less stressful and less impactful on tree water uptake and fruit yield compared with mechanical harvesting.