The 2011 ASHS Annual Conference

The demand for organic food products has increased within the past decade.  It is of interest to determine best management practices for organic orchards to provide information to producers.  Compared to conventional orchards, organic orchards have higher mycorrhizal colonization.  Currently, it is accepted that arbuscular mycorrhizal fungi (AMF) form a symbiotic relationship with a host plant that promotes root growth in the host, increases phosphorous and water uptake, provides pathogenic resistance, and provides stress resistance in exchange for carbohydrates.  Mulch is one of the primary elements of organic orchard management and provides ground cover, water retention, and a slow release nutrient source.  A mulch that provides a suitable environment for mycorrhizae in addition to these characteristics would be a key management tool in an organic orchard.  The objective of this research was to compare AMF colonization and apple tree growth under the influence of organic mulches.  Model plants of apple rootstocks (M106) were grown in a greenhouse in sterile media with one of three inoculant treatments and were treated with one of four mulch treatments.  The inoculant treatments were two different commercial inoculants and a control.  The mulch treatments were wood chips, compost, shredded paper and a control.  It was hypothesized that different mulch treatments would have variable influences on mycorrhization, plant growth, and nutrient uptake.  The presence, absence, and percent colonization of mycorrhizae in relation to plant growth and foliar nutrient content were evaluated.  In addition, the qualities of the two commercial inoculants were assessed for population establishment.  The findings of this experiment will be used to evaluate effective mulch treatments for an organic apple orchard to promote mycorrhizal symbiosis in order to enhance plant growth and health.