Ian Merwin, Herman M Cohn Professor of Horticulture, will present a Crop and Soil Sciences (CSS) seminar on Long-term impacts of groundcover management systems on orchard nutrient budgets, rootstock microbial communities, and productivity, Thursday, April 11, 2013, 12:20 – 1:10 pm, 135 Emerson Hall.
He will also be presenting a Department of Horticulture seminar on May 10, A retrospective on sustainability studies in orchards & vineyards, Friday, May 10.
The content of the two seminars “will be about 50 percent similar,” he says.
His abstract for the CSS seminar:
Since 1986 we have studied the long-term effects of different orchard groundcover/soil management systems (GMSs) on apple tree health and productivity, rootstock performance and rhizosphere microbial communities, and leaching, runoff, recycling and retention of nitrogen fertilizer and other agrichemicals. The short (3-5 year) vs. long-term (5-20 year) effects of GMSs on tree health and fruit production have been substantially different. Nitrogen and water competition from grass and legume groundcovers reduced fruit production and tree biomass up to 40% during orchard establishment, but in subsequent years tree root systems adapted to groundcover competition and yields were similar. Edaphic conditions diverged over time in herbicide vs. wood-chip mulch GMSs, with greater water infiltration, macroporosity, and soil organic matter in the mulch treatments. Rhizosphere microbial communities also differentiated over time among GMSs, and among various apple rootstock genotypes, and these differences influenced tree responses to the soil-borne disease complex known as apple replant disease. Detailed studies of N and P budgets under different GMSs have suggested that tree-row herbicide treatments required N fertilizers to maintain optimal fruit production, while grass and mulch GMSs had excess N supply after 15 years of treatments, and N leaching became a potential problem under wood-chip mulch. A recent short-term study of GMSs in steep hillside avocado orchards in central Chile showed that offsite soil erosion and runoff can be reduced by several orders of magnitude when groundcovers are maintained in these orchards, but there was also a concomitant reduction in early fruit production under the groundcovers compared with weed free herbicide systems. Taken collectively, our studies have important implications for the relative sustainability of different orchard floor systems, and the different short vs. long-term trends demonstrate the need for more long-term studies in perennial fruit-crop systems.
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