CULTIVAR, GROUND-COVER, AND IRRIGATION TREATMENTS AND THEIR INTERACTIONS AFFECT LONG-TERM PERFORMANCE OF PEACH-TREES

Three cultivars ('Garnet Beauty', 'Harbrite', 'Canadian Harmony'), two ground covers (temporary cover vs. permanent sod), and no irrigation vs. season-long trickle irrigation were studied in a high-density (633 trees/ha) peach [Prunus persica (L.) Batsch] orchard established on F ox sand in 1980. From 1985 to 1989, soil water content in the top 130 cm was similar in nonirrigated and trickle-irrigated plots except duri ng the growing season (May to September). Total soil water was lowest in nonirrigated plots that had permanent sod strips in the row middles and fell below the permanent wilting point for greater-than-or-equal- to 1 months in summer but not at depths below 130 cm. Trunk cross-sect ional area (TCA) was greater for 'Canadian Harmony' and 'Harbrite' tha n 'Garnet Beauty', ground-cover treatments had no effect, and irrigate d trees were generally larger than those not irrigated. Photosynthetic rate and stomatal conductance differed by cultivar, were unaffected b y ground cover, and were enhanced by irrigation. Defoliation differed by cultivar, ground cover had little effect, and irrigation usually de layed defoliation. Flower bud and shoot xylem hardiness differed by cu ltivar but not by ground cover and were generally enhanced by irrigati on. Tree survival was significantly affected by cultivar, being best w ith 'Harbrite' and 'Canadian Harmony' and poorest with 'Garnet Beauty' . Permanent sod enhanced tree survival while trickle irrigation reduce d it. Cumulative marketable yields were affected more by cultivar than by ground cover or irrigation. 'Canadian Harmony' had the highest yie ld, followed by 'Harbrite', then 'Garnet Beauty'. Yields in sod were s lightly higher than in temporary cover and yields with trickle irrigat ion were slightly higher than without irrigation. The best soil-manage ment system when TCA, marketable yield, and tree survival were conside red was a combination of permanent creeping red fescue sod strips in t he row middles and trickle irrigation in the tree row. This system is being recommended to commercial growers in southwestern Ontario.