10/29/2021 - By Dr. Tom Reed

Conclusion:

Sweet orange selection trial for Huanglongbing (HLB) tolerance on 20 ac that had major plantings in 2008 and 2010. Harrell’s controlled release fertilizer (CRF) was applied every six months. The blend was modified to enhance micronutrient content over time with the latest change being implemented in the spring 2018 application, where the Mn and Mg concentrations were increased. HLB has been present throughout trial since 2009. Historically a noticeable improvement in tree appearance has been observed with the use of Harrell’s CRF. Recently, considering the poor soluble solids encountered from many commercial groves around FL, the juice quality data from the various scion/rootstock combinations in this trial is quite relevant. For both scions (Vernia and Valquarius), the large majority of the rootstocks in this trial produced pounds solids/box between 6 and 7. This is far above the state average, and the positive results (now achieved in multiple years) are being attributed to the nutrition program being utilized. The Harrell’s CRF provides roots with elevated levels of all the important secondary and micronutrients year-round. The excellent fruit quality is even being observed on the rootstocks that have trees with thin canopies and lower yields

Figure 1: Harrell’s CRF applied every 6 Months utilized in sequence from left to right (3 on right contain Tiger-Sul micronutrients)