This project was initially awarded to Dr. Ferrarezi. Following Dr. Ferrarezi departure from UF/IFAS the project was transferred to Dr. Rossi. Finally, the project was early terminated in December 2021. The purpose of this project was to assess nitrogen (N) fertilization rates for high-density plantings of different scion and rootstock combinations in four commercial citrus growers. The overall approach was 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 in Spring 2021. Grower collaborators participating in the project were contacted in Spring 2021. The 4 growers comprised: 1) IMG Citrus (Mr. Brian Randolph), 2) Peace River Citrus (Mr. Larry Black Jr.), 3) Agromillora Florida/ Lost Lake Groves (Mr. Clay Pedersen), 4) Graves Brothers (Mr. David Howard). The graduate student and the research assistant scheduled and performed site visits to all locations in Spring 2021 and Summer 2021. 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 were requested to growers in Spring 2021. 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 COVID-19 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 were applied all locations in Summer 2021 and initial tree size and leaf area index data collection was performed as expected in Summer 2021. The project was early terminated by the CRDF Board at the end of the first year and money were returned to CRDF in January 2022.