ASHS 2024 Conference

The growing demand for affordable and healthy food to feed the growing population necessitates multilayered strategies to meet food demand and supply features: excessive irrigation application to overcome the impact of erratic rainfall, which imposes pressure on groundwater withdrawals, adversely affecting crop failure and sustainability. The objective of the study was to determine the impact of varying irrigation levels on tree growth, leaf nutrient concentrations, and water relations at selected citrus tree densities. The experiment was carried out on Malabar fine sand (sandy, siliceous, hyperthermic Arenic Alaquods) in a commercial citrus grove near Immokalee, FL, USA from 2019 to 2022. Mature thirteen-year-old ‘Valencia’ (Citrus sinensis) citrus trees grafted on Carrizo (a hybrid of Washington Navel orange and Poncirus trifoliata) planted in tree densities of 360, 485, and US-897 (Citrus reticulata Blanco x Poncirus trifoliata (L.) Raf.) citrus rootstock with 920 trees ha-1. Significant water distribution and movement were detected along the soil profile in response to the irrigation rates with higher volumetric water content on the grower standard highest irrigation. As a result, significant fibrous root length densities (FRLD) and median lifespan were observed in the three-row and two-row experiments with the deficit (50%-crop evapotranspiration, ETc) and moderate (78%-ETc) as compared with the grower standard highest (100%-ETc) irrigation regimes, respectively. Stomata conductance and stem water potential ( manifested less tree water stress when trees received moderate irrigation in the low and moderate tree densities than the highest tree density. This significantly impacted the FRLD in the soil and leaf area index (LAI) above the ground tree growth. Moderate irrigation triggered FRLD and improved root survival probability and lifespan. Meanwhile, nutrient uptake from the soil significantly affected leaf nutrient concentration when trees received moderate irrigation than deficit or highest irrigation rates. As a result, irrigation management improved water relations, leaf nutrient concentration, and tree growth across the varying irrigation regimes.