1. Please state project objectives and what work was done this quarter to address them: The overall goal of the project is to develop fertilization strategies to best match nutrient supply and demand, and develop recommendations for optimal nutrient application timing as compared to a simple constant supply, which will improve fruit yield, quality, and reduce fruit drop. A)Objective 1) Test if a reduced N-P-K nutrient supply in the fall is safe for sustaining HLB-affected citrus, and whether it can improve fruit quality to facilitate earlier maturity / harvesting and reduce fruit drop:In order to compare the effects of early versus late / sustained fertilization on health and fruit production of Hamlin and Valencia trees, the following completed treatments were evaluated in the fourth quarter of 2022:Treatments: Early fertilization as % completed of the recommended fertilization (RF; 160 lb N/acre) before June T1: 25% of RF (T25%)T2: 50% of RF (T50%)T3: 75% of RF (T75%)T4: 100% of RF (T100%)During the fourth quarter of 2022, the trees in the experiment were recovering from substantial damage caused by hurricane Ian in late September, and were impacted again by hurricane Nicole in October. The Hamlin trees lost most of their fruit due to the onset of maturity making them most vulnerable to drop. The Valencia trees retained more fruit, but losses were also significant. The Sugarbelle trees suffered considerable limb and tree breakage, as well as fruit drop. Fruit drop occurred during the storm events, and continued for weeks afterwards as the stress caused premature coloring and abscission. Soil lysimeter leachate sampling, leaf sampling, processing and analysis continued, and tree size and health was assessed after the third Aerobotics drone survey was completed in November. Since many of the Hamlin plots had no fruit remaining at all, we could only sample the few remaining fruit for analysis and observational comparison of fruit quality. In December we harvested Sugarbelle fruit from experiment plots to assess the efficacy of foliar nutrient sprays (P and K) and gibberellic acid (GA) on fruit peel firmness, color, and internal fruit quality. The peel strength measurements conducted with a digital penetrometer were NS and inconclusive, mainly due to the unsuitability of measuring only force (N) to puncture the peel. We plan to measure future fruit peel strength by quantifying the force required to distort the peel by an exact fixed distance. That will allow the calculation of work done, or energy expended (J), which is a more reasonable measure of peel strength / firmness. GA applied once at 10 ppm in August significantly reduced TSS relative to the two best treatments, dipotassium phosphate (DKP) sprayed in May, July and September, and potassium nitrate sprayed in July. The GA treatment had the lowest TSS overall. Titrateable acidity, TSS/acid ratio, and fruit weight were NS across treatments. Objective 2) Develop an optimized, practical fertilizer timing management profile to boost fruit quality and reduce fruit drop for HLB-affected citrus based in part on the sigmoidal nutrient demand curve defined by four physiological growth phases (0=bloom/fruit set; 1=cell division; 2=cell enlargement; 3=maturation):The growth and yield data associated with all different timed fertilizer events in year 1 is not complete yet and was severely impacted by hurricanes, and therefore we don’t have new results to report for this objective. B) New developments: NoneC) Issues: The severe damage caused by hurricanes in 2022 will likely cause longer-term setbacks to the trees in these experiments.2. Please state what work is anticipated for next quarter: The first 2023 season fertilizer applications will be made to designated treatment plots in February. Soil, lysimeter sampling, leaf sampling, processing and analysis will be ongoing, as will tree size and fruit measurement. We plan to assess fruit yield and quality for the Valencia experiment if enough fruit remains. In Feb/Mar the roots of the Hamlin and Valencia trials will be sampled at two soil depths by collecting and sieving soil samples taken around the driplines of trees. We plan to apply OTC by trunk injection to all the trees in Hamlin and Valencia trials, since this remedy is now labeled and available, and will likely be the new norm for growing citrus in HLB-endemic Florida. The OTC will be applied to all trees, similar to the way herbicide, pesticide, or irrigation is applied to all trees irrespective of treatment. 3. Please state budget status (underspend or overspend, and why): Spending rate is approximately on track.