Orchard floor management in young peach [Prunus persica (L.) Batsch.]: Effects of irrigation, vegetation-free width, and certain PRE herbicides

A hindrance to peach culture in the southeastern U.S. is orchard floor vegetation in which weeds can compete for water and nutrients. Young orchards may take longer to come into production if infested with weeds. The common orchard floor management system in the southeastern U.S. is a 3.0 to 3.6 m wide vegetation-free strip in the tree row with an orchard cover of volunteer weedy vegetation. However, reduction of the strip width may be possible through the use of irrigation which could reduce herbicide use. Thus, the objective of this study was to determine the optimum vegetation-free strip for irrigated peach with a weedy groundcover. Research was conducted in 2006 to 2008 to determine the optimum vegetation-free strip for irrigated peach with a weedy groundcover, and to evaluate PRE-emergence directed control of weeds that infest peach in North Carolina.;The first experiment included two factors, vegetation-free widths (VFW) of 0, 0.6, 1.2, 2.4, 3, and 3.6 m and irrigation (either irrigated or nonirrigated). At Jackson Springs, NC, the irrigated VFW which would produce the same yield season total (kg/ha) as the grower standard (3.6 nonirrigated) is 1.16 m, based on results from regression. (For maximum season total, the VFW needed to be 3.6 m.) The irrigated VFWs which would produce the same tree cross-sectional area (TCSA) as the grower standard was 1.5, 1.3 and 0.8 m for trees aged one, two, and three years old, respectively. At Clayton, NC, TCSA in 2007 and 2008 and harvest season totals were not different by irrigation, but did increase linearly with VFW. At both locations, water and nitrogen were probably the limiting factors. Similar across locations, leaf nitrogen concentrations were lower but not deficient in the irrigated trees than the nonirrigated trees, presumably due to leaching of NO3 by irrigation. Foliar N, SPAD measurements, soil moisture, and growth responses were positively related to VFW at Jackson Springs therefore growth responses there were probably due to water and N competition with vegetation. In contrast, foliar N concentration was not different by VFW at Clayton. However, growth responses were positively related to VFW. SPAD measurements increased with VFW so vegetation had some effect on nitrogen. For the first two years of the study, VFW did have an effect on soil moisture at 30 cm depth. Data suggest that a 1.5 m VFW combined with proper irrigation and fertilization will produce tree growth and yield in volunteer weedy vegetation similar to the current grower standard.;The second set of experiments was conducted to determine newly planted peach tolerance to sulfentrazone herbicide applied PRE at various rates and to determine the effect of sequential sulfentrazone when tank mixed with other PRE herbicides (norflurazon, oryzalin, terbacil, rimsulfuron, or flumioxazin). Sulfentrazone PRE did not injure newly planted peach trees. Sulfentrazone alone controlled several broadleaf weeds however it did not adequately control large crabgrass and yellow foxtail. Control of these grasses increased with the addition of norflurazon or oryzalin.;The third set of experiments was conducted to determine tolerance to halosulfuron, mesotrione, and rimsulfuron applied at various rates on newly planted peach. No herbicide reduced TCSA or winter pruning weight relative to the nontreated check. In 2006, some foliar injury from halosulfuron occurred at the higher rates. No visual injury symptoms occurred in 2007 for any study.;Mesotrione, rimsulfuron, and sulfentrazone were safe to newly planted peach and likely would be useful to growers developing weed management programs for peach.