Submitted to: Scientia Horticulturae
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/28/2010
Publication Date: 8/26/2010
Publication URL: 10.1016/j.scienta.2010.06.020
Citation: Tworkoski, T., Glenn, D.M. 2010. Long-term effects of managed grass competition and two pruning methods on growth and yield of peach trees. Scientia Horticulturae 126:130-137. Interpretive Summary: Peach tree size must be managed to control growth of fruit-bearing branches which is important to sustain productivity and profitability for growers. Pruning is the principle means to control peach tree size but repeated, heavy pruning promotes dense shoot growth that can adversely affect fruit size and quality. Managed ground cover (grass) competition combined with pruning may be used to control the size of the peach trees while reducing the counterproductive excess shoot growth. This experiment was designed to improve knowledge of the relations between grass competition, pruning, and tree age to reduce adverse effects of heavy pruning. In this experiment growth and yield were measured in two peach cultivars managed with two pruning methods (conventional and reduced) and two levels of grass competition that were imposed in young and mature orchards. The numbers of commercially acceptable fruit per tree were reduced by grass competition but reduced pruning could offset this yield loss over the lifetime of the orchard. Grass competition reduced dense shoot growth and the pruning time per tree but an economic analysis of labor savings and fruit size loss is necessary before grower recommendations can be made. The results indicate that pruning and crop load can be adjusted to ground cover competition to obtain target yield and fruit sizes.
Technical Abstract: Ground cover competition and tree training strongly affect development of newly-planted peach trees and eventual productivity of peach orchards. This experiment characterized the long-term interactive effects of two levels of competition (applied to young and mature trees) and two pruning criteria on tree crop load and average weight of marketable fruit. To compare effects of early, persistent competition, trees of two cultivars ('Jersey Dawn' and 'Redskin' on Lovell) of peach (Prunus persica (L.) Batsch) were planted in an orchard in 1993 and grown for 14 years in a vegetation free area (VFA) width of 0.6 or 2.4 m. To compare late, persistent competition, a separate group of trees were planted in 1993, grown in a 2.4 m VFA until 1998 when soil beneath half the trees was seeded with grass and then grown for 9 years. To evaluate interactive effects of competition and pruning, all trees were pruned to maintain canopy size with wide-angled scaffold limbs and intense pruning (IP) or upright branch form with reduced pruning (RP). In general, ‘Redskin’ had greater yield than ‘Jersey Dawn’ and, as expected, growth and yield increased with increased size of VFA with early, persistent competition. With increasing time, cumulative yield of both cultivars was similar in RP trees in 0.6 m VFA and IP trees in 2.4 m VFA. Average marketable fruit weight response to crop loads was similar with or without grass competition. Within each pruning treatment and cultivar, grass competition reduced the number of marketable fruit without affecting average weight of marketable fruit. Yield and fruit sizing responses to pruning treatments were similar when competition was delayed and applied to more mature peach trees although, in general, competition reduced tree size and crop load more in young than mature trees. The results indicate that persistent competition will reduce annual yield but reduced pruning and the concomitant increased crop load can counter this effect. The increased crop load reduced average fruit weight but the rate of fruit weight decrease was uncoupled from grass competition. Grass or alternative ground covers beneath peach trees will impose competition but coordination of pruning and fruit thinning can achieve desired cropping and fruit size.