Pecan Shell Mulch Affects Peach Tree Growth, Yield, and Survival

Pecan shells are a waste product that are occasionally used for mulch in ornamental landscape settings; yet most shell waste is left in piles near the shelling facility or discarded by other methods.  If another use for this waste product could be developed, it may lead to added income for pecan producers.  A peach orchard was planted at a spacing of 5.5 m x 6.8 m in Feb. 2005 at the Cimarron Valley Research Station in Perkins, Okla. consisting of several different cultivars on ‘Halford’ rootstock.  From this orchard, the ‘Loring’ block was chosen to determine what effect pecan mulch would have on peach trees.  Five treatments were imposed: no herbicide, no mulch, mow only (Trt 1), herbicide (glyphosate) (Trt 2), 1.8 m x 1.8 m x 5 cm deep mulch (Trt 3), 1.8 m x 1.8 m x 10 cm deep mulch (Trt 4), and 1.8 m x 1.8 m x 15 cm deep mulch (Trt 5).  All blooms and fruit were eliminated by frosts or freezes in 2006 and 2007.  Yields in 2008 revealed that Trt 1 was statistically the poorest option (13.2 kg/tree and 93 fruit/tree).  All other treatments did not differ, but Trt 4 had the highest mean yield (26.4 kg/tree and 195 fruit/tree).  Fruit quality (°brix) and fruit weight did not differ by treatment.  Tree growth parameters of tree height, pruning weights, and trunk caliper were not statistically different with the exception of Trt 1 which was significantly less in all three categories beginning in 2007.  Tree mortality increased with depth of pecan mulch.  Treatments 1-3 had little tree loss (0-5%), whereas Trt 4 and Trt 5 had increased mortality (15% and 35%, respectively).  The primary reason for mortality was likely due to record rains in 2007 coupled with the longer moisture retention from deeper mulch.