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Title: EFFECTS OF VINEYARD FLOOR MANAGEMENT ON MYCORRHIZAL FUNGI IN A CENTRAL COAST, CALIFORNIA VINEYARD

Author
item Baumgartner, Kendra
item SMITH, RICHARD - UC COOP EXT, MONTEREY, CA
item BETTIGA, LARRY - UC COOP EXT, MONTEREY, CA

Submitted to: American Society of Enology and Viticulture Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/15/2003
Publication Date: 6/18/2003
Citation: Baumgartner, K., Smith, R.F., Bettiga, L. 2003. Effects of vineyard floor management on mycorrhizal fungi in a central coast, california vineyard. American Society of Enology and Viticulture Annual Meeting Abstracts.

Interpretive Summary: Vineyard weed control and cover cropping practices affect natural populations of soil microbes, some of which play key roles in making soil nutrients available to grapevines. Arbuscular mycorrhizal (AM) fungi represent one specific group of soil microbes that colonize grapevine roots, enabling more efficient phosphorus uptake which, in turn, improves grapevine growth. Effects of vineyard weed control practices are likely indirect (killing weeds that host AM fungi). Vineyard cover crops that host AM fungi on their roots may increase populations of AM fungi in vineyard soil. The objective of our research is to compare the effects of three cover crop treatments (bare ground or no cover crop, Secale cereale cv. 'Merced rye', X Triticosecale cv.'Trios 102') and three weed control treatments (preemergence herbicides, postemergence herbicides, mechanical cultivation) on AM fungi in grapevine roots. Treatments were applied to grapevines in a Central Coast, California chardonnay vineyard. In summer 2002, we began to examine AM fungi in grapevine roots, cover crop roots, and vineyard soil. Based on preliminary analysis of summer and fall 2002 data, weed control had a significant effect on AM fungi in grapevine roots and vineyard soil. Vines in rows treated with preemergence herbicides had significantly lower root colonization and lower weed frequency than vines in cultivated rows. These results show that weeds are important source of AM fungi in vineyards. Cover crop treatment had no effect on mycorrhizal colonization of grapevine roots, but it did affect the concentration of spores in the soil underneath the cover crops. Given that we found no grapevine roots near cover crop roots, it appears that lack of contact between their root systems prevented significant effects of cover crops on colonization of grapevine roots.

Technical Abstract: Vineyard floor management impacts soil chemical, physical, and biological properties. Cover crops enhance soil chemical properties (e.g. nitrogen input for legumes), physical properties (e.g. soil organic matter), and may increase populations of beneficial soil microbes, such as arbuscular mycorrhizal (AM) fungi. Assuming that grapevine and cover crop AM fungal communities and fine root distributions overlap, cover crops may increase colonization of grapevine roots, thereby providing grapevines with benefits of hosting AM fungi (e.g. improved water relations, increased phosphorus uptake). Effects of weed control may be direct (disturbing AM hyphal networks with mechanical cultivation) or indirect (killing weeds that host AM fungi). Our objective is to compare the effects of three cover crop treatments (bare ground, Secale cereale cv. 'Merced rye', X Triticosecale cv.'Trios 102') and three weed control treatments (preemergence herbicides, postemergence herbicides, mechanical cultivation) on AM fungi in grapevine roots. Treatments are arranged in a split-block design with 3 blocks (weed control as main plot, cover crop as subplot). In summer 2002, we began seasonal quantification of AM fungi in vineyard rows and middles. Based on preliminary analysis of summer and fall 2002 data, weed control had a significant effect on mean percent root colonization of grapevines. Vines in rows treated with preemergence herbicides had significantly lower mean percent root colonization than vines in cultivated rows. Cover crop had no effect on mean percent root colonization, which is likely a function of no overlap between grapevine and cover crop fine root distribution.