One of the newest ACPS field experiments was planted with ‘Valencia’ orange in August 2012 near Lake Alfred. Its primary objective was to test innovative super-high density citrus grove replanting configurations with a drip fertigation open hydroponics (OH) system for maximizing early return on investment for processed oranges in a canker and HLB-endemic disease environment. Treatments consist of the following: Main source of N: 1) calcium nitrate, 2) ammonium nitrate Rootstocks: 1) Swingle, 2) US897 Planting geometry / density: 1) 484 trees/acre in straight rows, 2) 538 trees/acre in dual tramlines The trees were established to receive all their fertilizer through drip fertigation (2×0.5 gph/tree), and a second microsprinkler irrigation system was installed for freeze protection. The ‘Valencia’ trees grew out very well and by the end of the second year already had a harvestable fruit crop, to be picked in about March 2015. In September 2014, two years after planting, the following tree canopy measurements were analyzed: Table 1: Tree canopy volume in cubic meters/tree showing significant rootstock x fertilizer response Rootstk Fert CaN AN US897 2.615 2.571 Swingle 3.277 2.921 Table 2: Tree canopy volume in cubic meters/tree showing significant effect of tree planting geometry Plant Straight Tram 2.744 3.020 The results show an improvement in tree canopy growth from using calcium nitrate versus ammonium nitrate for both rootstocks, but that the Swingle rootstock grew larger canopies than US897. The tramline configuration also produced slightly larger canopies than the straight hedgerows. We will continue monitoring these trends in subsequent seasons as the trees mature and fruit production increases. Unfortunately the incidence of HLB was established through visual symptoms at 30% in November 2014, after only 26 months. We could not detect differences in HLB severity or incidence that related to the treatments. Future management plans for HLB in this block will involve more intense foliar and root fertilization with, particularly the metal micronutrients.