The purpose of this project is to assess nitrogen (N) fertilization rates for high-density plantings of different scion and rootstock combinations in four commercial citrus growers. The overall approach is to 1) determine the appropriate N rates needed to support tree growth and productivity, 2) compare data obtained with existing UF/IFAS N recommendations, and 3) revise best management practices (BMPs) for N application in young trees planted in high-density plantings affected by Huanglongbing (HLB). The Ph.D. student and Research Assistant dedicated to the project were hired. We contacted the grower collaborators participating in the project: IMG Citrus (Brian Randolph), Peace River Citrus (Larry Black Jr.), Agromillora Florida/ Lost Lake Groves (Clay Pedersen), Graves Brothers (David Howard), and scheduled/performed site visits to all locations. The planting densities and variety/scion combinations were chosen, field maps generated, experimental units identified with permanent signs, and the current information regarding N fertilization requested to proceed with the treatment applications. Dr. Ferrarezi contacted Yara (Bill Easterwood) and received fertilizer donations for the first year (20 tons or 40k lbs). Unfortunately, the delivery was delayed due to logistics finding a local distributor, blending the four different formulations, and delivering in Fort Pierce. We were able to receive both calcium nitrate and ammonium nitrate despite the challenges of finding this fertilizer. That was only possible because of the partnership with Yara. Treatments are in the process of being applied in all locations; we should complete the 2nd fertilization for the season on 07/16/2021. The first tree size and leaf area index data collection was performed as expected. We contacted AgerPoint to collect tree size data using Lidar sensors potentially, but the cost was prohibitive. We partnered up with AeroBotics to analyze images collected from drones. The project is on schedule.