Abstract
Current practices of fertilizer management, potential problems, and paths for fertilizer management research were discussed. Apple nutrition management in the humid southern regions of the U.S. is typically challenged by several factors such as inherently low soil pH, variable soil chemistry, and irregular precipitation. Some literature and personal experiences with orchard replant conditions and fumigation, fertigation, fertilizer delivery system, and time of fertilizer application were reviewed. On replant sites, fumigation and liming significantly improved tree survival and growth in the first 5 years. Fertigation with ammonium nitrate significantly lowered soil pH in the root zone compared to top dress applications. Using calcium nitrate resulted in less pH reduction. Results of studies of autumn application of N fertilizers have been mixed, with reports of no, decreased, or increased effects on fruit set, yield, and growth. Studies with size-controlling rootstocks indicate additional need to study the uptake of Mn and related Mn toxicity. Precocious rootstocks with high early yields have resulted in foliar K levels approaching deficiency within the first 10 years of production. Indications are that high-density orchards may have additional requirements for K fertilizers.
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