The profit potential of pecan increased in 2009 with sudden growth in the Asian pecan export market. As a result, there has been a renewed interest in the crop, which has led to the planting of additional pecan acreage throughout the United States pecan belt (USDA, 2012; Wells, 2014). Georgia pecan producers planted at least 391,488 pecan trees and 6203 additional pecan ha from 2010 to 2014. These new plantings coincided with a shift toward the planting of pecan trees at higher density by Georgia pecan producers since 2010 in anticipation of maintaining these densities through hedge pruning (Wells, 2014).
As pecan trees grow in an orchard, their tree canopies encroach on one another, causing excessive shading, which has been shown to increase alternate bearing intensity and reduce tree health and orchard profitability (Pearce and Dobersek-Urbanc, 1967; Wood and Stahmann, 2004). Historically, limb pruning and tree removal have been the solution to this problem, particularly in the low-light environment of the southeastern United States (Wells, 2007). Mechanical hedge pruning has been used successfully in high-light environments to mitigate the effects of orchard shading (Wood and Stahmann, 2004) and has become the standard method used for this purpose in the arid production regions of the western United States (Andales et al., 2006; Herrera and White, 2000).
Mature pecan orchard canopies typically intercept 65% to 70% of available sunlight (Wood, 1996) with up to 95% light interception in overcrowded, unpruned orchards (Lombardini, 2006). The southeastern United States is a relatively low-light environment, exhibiting significant cloud cover and atmospheric water vapor throughout the growing season, which can further limit sunlight in orchard systems (Wood, 2009). Initial studies of mechanical hedge pruning in these low-light environments have failed to show significant benefits to pecan production. Worley (1985) determined that annual cuts to one of each of four sides of the canopy and topping at 6 m was unsuitable for southeastern commercial pecan orchards. Lombardini (2006) found that one-time mechanical hedge pruning of nonirrigated pecan trees initially increased light within tree canopies but did not increase orchard productivity, nut yield, or quality. Wood (2009) suggested that moderate-width (2.4 m from the tree axis), short-cycle (annual or biennial pruning) mechanical hedging did not appear efficacious for southeastern pecan production in the short term; however, it would be likely that over the long term, it would prove superior to nonpruned trees. Anecdotal experience by pecan producers in the southeastern United States following 2010 suggested a promising approach for mechanical hedge pruning in the region, which has since led to an increase in popularity of the hedge-pruned system among growers (Stevenson, 2013). Bock et al. (2017) found a reduced risk of pecan scab (Fusicladium effusum G. Winter) with hedge pruning of pecans in Georgia as a result of enhanced fungicide coverage through a reduction in tree size.
Pecans are a relatively high water use crop (Wang et al., 2007). As a result, irrigation is one of the most important management tools used in pecan production and results in increased nut size, yield, nut quality, and precocity (Alben, 1957; Brison, 1974; Daniell et al., 1979; Stein et al., 1989; Wells, 2015; Worley, 1982). Water stress in pecan is correlated with soil moisture from budbreak through the end of nut sizing. Pecan trees bearing a moderate to heavy crop load may undergo water stress during the kernel filling stage regardless of soil moisture level (Wells, 2015). Management practices that alleviate water stress have the potential to improve pecan production.
The objectives of this study were to compare the effects of hedge pruning on pecan nut quality, yield, and midday stem water potential of pecan trees in the temperate climate of the southeastern United States and to evaluate the effect of hedge pruning on windstorm damage to pecan trees.
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