Issue link: https://read.dmtmag.com/i/629538
16 FEBRUARY 1, 2016 GOOD FRUIT GROWER www.goodfruit.com M anaging irrigation and nutrients for grapes can be tricky anytime — even more so in a drought year like the one last year in Washington. The key to ensuring vineyards receive the necessary water and nutrients lies underground at the roots. For two years, Washington State University soil scientist Joan Davenport and a research team sampled Concord roots on 42-year-old vines at different points in the growing season to better understand when roots are working most actively to support the vine. While Davenport focused on Concord grapes for the study, the findings relate to wine grapes as well. The takeaway: Growers must remember their roots are distributed over a much wider area than they probably think, which affects how and when they apply nutrients and water, Davenport told growers at the Washington State Grape Society annual meeting in November. Types of roots Grapevines have a lot of different roots. The big roots, called coarse roots, help serve as the sturdy backbone of the plant, while the finer roots are the feeder roots that take up the majority of water and nutrients. Overall, root distribution decreases as they grow farther from the trunk at deeper depths, but that growth is influenced by water. To better understand how those roots develop during the season, Davenport and her research team dug up an average of four Concord vines from a furrow-irrigated vineyard at different points in the season: in win- ter, at bud break in early spring, when vines showed three to four leaves in late April, at bloom, at veraison, at harvest (in about mid-September) and at postharvest, before the vines had gone dormant. They excavated the entire root ball, measured the length of roots and weighed coarse roots. They also collected soil samples, in a radial pattern out from the trunk, for fine and some coarse roots and separated them from the soil. Davenport said she expected to find fine roots in the first 8 inches below the surface but was surprised to find them even beyond that. Overall, roots were found 1 yard deep. However, roots decrease farther from the trunk and deeper below the surface of the soil. "As a general rule of thumb, the further out from the trunk you go and the deeper you go, the fewer roots you have," she said. Coarse roots The density of coarse roots was greatest at bud break, with 6 linear feet of roots in a cubic yard of soil. The second-highest density of coarse roots was found directly preceding bud break in late winter. The lowest point was at harvest. "When we have some of that early growth, the plants are actually using a little bit of those root materials to feed the growth," Davenport said. The team generally found that more coarse roots were found closer to the vine trunk and diminished with greater distance from the trunk. They also decreased at greater depths. ROOTS of a vineyard Viticulture Volume of fine and coarse roots varies during season. by Shannon Dininny Digging into the Toll-Free: 877-552-4828 909-464-1373 • Fax: 909-464-1603 http://www.agfast.com For your nearest dealer, contact: Trellis & Fence Wire Anchor This trellis and fence wire anchor securely holds wires to end-posts. Insert the wire into and through the wirevise. It automatically locks onto the wire. No tools required. To tighten, just pull more wire through the vise. A release tool is available from AgFast for 12-16 gauge wire. • 11-1/2" Length • UV Stabilized (Made to last) • Easy Tie & Re-Tie • Economical GREENTIE™ WIREVISE™ GreenTieWireVisead.qxp_Layout 1 1/7/16 4:50 PM Page 1