The 2009 ASHS Annual Conference

Major limitations to successful establishment in an organic orchard are weed vegetation competing with the tree and sufficient nutrients required for growth.  Both affect growth, development and early cropping.   Trees of ‘Enterprise’/M26 planted at 600 trees/acre (1480 trees/ha) in 2006 and trained to a modified vertical axis were planted.  Trees were treated with an interaction of ground cover management systems and nutrient sources.  The ground cover management treatments were 1) urban green compost (GC), 2) wood chips (WC), 3) shredded paper (SP), or 4) a managed fescue and clover vegetation providing mulch through mowing (MB).  Nutrients were provided by 1) a control (NF), 2) composted poultry litter (PL), or 3) an organic approved poultry-product based commercial fertilizer (CF).  In the NF treatment, nutrients were to be derived solely from the ground cover management treatments.  The orchard was managed as certified organic.  The results of growth and production in the first three years are presented.  Trees with GC or WC were tallest after two seasons and achieved growth target of 3.1m while those with SP or MB did not.  Likewise, tree width GC and WC had the largest TCSA in each of the first three seasons.  Trees with SP suffered significant freeze injury during a spring freeze event in 2007 while trees with other treatments did not.  After two seasons, trees with GC or WC were determined to be horticulturaly large enough to crop while those with SP and MB did not fill their allotted space.   Trees with SP exhibited less foliar chlorophyll and lower assimilation rates during mid-summer.   In the third growing season, trees with GC and WC had 2 to 4 times more flower clusters per tree, and significantly higher fruit set.  Trees treated with SP and MB did not crop in the third year while those with GC and WC did with similar yields and cropping efficiencies.   Tree height was not significantly affected by nutrient source treatments although the NF trees were the shortest and had significantly less TCSA.  The NF treated trees had fewer flowers per tree and less fruit set per tree.  However, yield per tree was similar among all nutrient source treatments due to increased fruit size with reduced cropping in the NF treated trees.