ASHS 2024 Conference

Concerns about eutrophication that causes blooms of blue-green algae have strengthened over the last several decades due to the excessive use of pesticides and fertilizers, particularly those containing nitrogen (N) and phosphorus (P). These substances leached from agricultural fields and citrus groves into groundwater sources. Consequently, researchers developed best management practices (BMP) which are now being used to safeguard the environment while raising agricultural productivity. Additionally, Florida citrus production has decreased by more than 70% due to huanglongbing (HLB). Macro and micronutrient uptake is constrained owing to the decreased fibrous root density which may inflict root loss of up to 80%, depending on the severity of HLB-affected trees. The standard recommended rates of N and P were developed before the incidence of HLB and are no longer valid and warrant further refinement. Therefore, new site-specific guidelines are needed for the present situation. A study was started on 11-year-old ‘Valencia’ sweet orange trees (Citrus sinensis (L.) Osbeck) on Swingle citrumelo (Citrus paradisi Macf. × Poncirus trifoliata L. Raf.) rootstock in central Florida on Candler fine sand in 2023 to evaluate the impact of N and P fertilization on the growth and yield of HLB-affected citrus trees as well as to determine the optimal N and P rates for HLB-affected citrus trees in Florida. Eight treatments will be used over three years, with two N rates (112 and 224 kg/ha) as main plots and four P rates (0, 8.9, 17.8, and 35.7 kg/ha) as subplots in a factorial randomized complete block design. Tree height, canopy size, trunk diameter, fruit output, and juice quality are among the variables that will be measured. We anticipate that treatments that receive additional fertilization over the current recommendation have a significant chance of enhancing citrus growth and production. Keywords: Best management practices (BMP), Citrus sinensis, Huanglongbing, Site-specific nutrient management.