The 2009 ASHS Annual Conference

The basic organic approach for development of organic crop production systems requires balance of both soil nutrients and beneficial soil microbes.  Achieving such a balance results in a soil and crop with improved health having greater resistance to disease and insects.  In 2002 USDA-ARS began using this approach to convert a 17-year old conventionally managed pecan orchard to organic.  Compost tea was soil applied three times each year through the irrigation system and monthly as a foliar spray uniformly across all treatments.  Yields harvested from individual trees indicated that, in general, applications of 168 kg/ha of nitrogen from three applications of ammonium sulfate (the conventionally managed control) resulted in the lowest yields, whereas application of 1120 kg/ha poultry litter applied twice yearly with mycorrhizal fungi gave the greatest pecan yield.  In 2008 comparing yields with the conventionally-managed (no compost tea) and organic orchards showed a 6.7 times increase for ‘Desirable’ and 3.8 times for ‘Cheyenne’ for the organic orchard.  Pests were controlled partially through improved soil and plant health and with the addition of biopesticides and biocontrol agents, for example pecan casebearer through release of trichogramma wasps and one 0.0146 l/ha foliar application of spinosad, and pecan weevils through soil applications of compost tea.  Pecan scab was partially controlled with compost tea and additional studies must be conducted.  In summary, the grower must remember that organic production is a system with highly significant interactions among components and attempting an individual component control taken out of the system will result in failure.