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:Routine measurements of tree health and performance continued, including leaf nutrient analyses, chlorophyll index, canopy and trunk size, fruit growth rates and incidental fruit drop (not pre-harvest). The study comprehensively analyzed the nutrient dynamics of leaves, revealing notable variations in nitrogen (N) concentrations. During the cell-division stage / physiological fruit drop in May to the cell-enlargement stage starting June, both Hamlin and Valencia varieties exhibited higher leaf N concentrations in most fertilization treatments, except for two linear supply treatments (T1 and T2). This increase in leaf nitrogen could contribute to enhanced crop health and performance. In contrast, potassium (K) concentrations in leaves remained consistent across various fertilization treatments throughout the growing period. However, a spike in leaf K concentration was observed in both Hamlin and Valencia during the fruit maturation phase (September-), particularly in treatments with linear nutrient supply and late fertilization. This is significant given that numerous studies indicate that lower potassium levels are preferable for improved fruit quality and peel coloration. Conversely, the temporal fluctuations of other nutrients did not show significant variations across different fertilization 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):In the 2023 growing season, an increase in fruit drop was observed in both Hamlin and Valencia varieties as the season progressed. Specifically, the lowest cumulative fruit drop per tree in Hamlin was recorded under treatment 3 (100% sigmoidal fertilizer supply). On the other hand, Valencia showed a higher cumulative fruit drop per tree, particularly in the linear supply with late fertilization treatment (T2). The overall percentage of fruit drop will be determined after the harvest.Regarding fruit growth, no significant differences were observed in the relative fruit growth rate among the various fertilization treatments. B) New developments: NoneC) Issues: None2. Please state what work is anticipated for next quarter:Routine lysimeter sampling, leaf sampling, processing and analysis will be ongoing, as will tree size, root growth and fruit drop and growth measurement.Plan for October to December:1. Sampling for leaf nutrient analysis2. Fruit diameter measurement3. Collection of leachates for nitrate N loss and analysis4. Scanning of the Minirhizotron for root growth5. Fruit drop count in every two weeks till harvesting in Hamlin and Valencia6. Harvesting Hamlin variety for yield and fruit quality measurement7. Soil sample collection from Hamlin variety blockIn the Sugar Belle peel thickness experiment, all treatment allocation was completed for this year’s experiment and final harvesting will be done during December for fruit quality and peel thickness measurements. Leaf sample collection will be done after harvesting of fruits and processed for leaf nutrient concentration. 3. Please state budget status (underspend or overspend, and why):Spending rate is approximately on track.