ARS | Publication request: Mechanical hedge pruning of pecan in a relatively low-light environment

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 22, 2008
Publication Date: January 30, 2009
Citation: Wood, B.W. 2009. Mechanical hedge pruning of pecan in a relatively low-light environment. HortScience. 44(1):68-72.

Interpretive Summary: The loss of nutmeat yield and quality, and enhanced alternate bearing, is a problem in commercial pecan orchards. This is especially true for orchards in low-light environments, such as the southeastern U.S. Several mechanical hedge-type prunings were evaluated using ‘Desirable’ cv. in a low-light environment. Narrow-canopy short-cycle mechanized hedgerow pruning offered a mixture of positive and negative effects, which included a reduction in the severity of alternate bearing. The approach is generally unacceptable for commercial enterprises in the southeastern U.S.; however, evidence indicated that a wide-canopy pruning approach is likely a viable alternative to tree removal.

Technical Abstract: Long-term productivity of commercial pecan [Carya illinoinensis (Wangenh.) K. Koch] enterprises in relatively low-light environments, such as the southeastern U.S., is limited by excessive tree crowding as orchards age. An effective horticultural strategy for countering this problem in relatively high-light environments is mechanical hedge-type pruning; however, uncertainty persists regarding the best strategies in low-light environments. This report describes the results of a four-year study regarding the response of ˜ 25-year-old ‘Desirable’ pecan trees to different mechanical hedgerow-type, moderate canopy width (i.e., 2.43 m cuts from tree axis), pruning strategies. Canopy treatments were non-pruned control (NPC), annual dormant season side-hedge pruning on two faces (HD), annual summer season side-hedge pruning on two faces (HS), and alternating annual dormant season side-hedge pruning on a single alternating face (HD2). Relative to the NPC treatment, all three pruning strategies: a) reduced in-shell nut yields by roughly 19-38%; b) reduced marketable nut-meat yield by about 19-36%; c) failed to stimulate shoot development or fruiting within the central interior zone of tree canopies; d) increased kernel percentage of nuts; e) increased nut-meat grade; f) substantially reduced alternate bearing intensity (0.51 to ˜ 0.20); and g) reduced orchard crowding. Pruning associated reductions in nut yield appear sufficient to limit the commercial usefulness of annual or biennial mechanical hedgerow-type pruning of ‘Desirable’ pecan orchards at moderate canopy widths in relatively low-light environments such as the southeastern U.S.