PULLMAN, Wash. — Vineyard floor management can be divided into two areas, the area under the vine and the area between the rows. Cover crops are often planted between the rows and mowed as needed during the season. Under the grapevines, a two- to four-foot strip is kept weed-free with herbicide applications. The most widely used herbicide in vineyards is glyphosate; it is cost-effective, controls many weed species, is environmentally friendly, and has low human toxicity . However, there is a growing debate in the scientific community about glyphosate impacts on human health and reports of glyphosate and the presence of its metabolites in the food supply .Mechanical cultivation is one option to replace or to complement chemical weed control under the vines. A variety of vineyard under-vine cultivators are available on the market. Weed control efficacy depends on plant species and operation timing, but no single piece of equipment will control all weed species or be compatible with all vineyard layouts. There is limited research in mechanical in under vine weed control options.
A project funded by Western Sustainable Agriculture Research and Education (WSARE, project number OW18-019) was initiated in 2018 to improve our understanding of the applications and limitations of under-trellis cultivators in Oregon vineyards. A total of six treatments were included: brush weeder, rotary tiller, hoeing blade, in-row mower, hoeing blade with rotary tiller, and a non-treated reference. Each side of the vine row was cultivated once with an ID David in row weeder with a single-side hydraulic articulating arm mounted on the rear of the tractor (Figure 1).Among all implements, the best performance was observed when soil volumetric water content was below 30% in a silt clay soil. Rainfall, which occurred after cultivation, appeared to impact efficacy, as it supported weed regrowth or new seedlings. Cultivation early in the season was less effective in part because of significant rainfall in the weeks following the treatment. The highest level of control was observed with the hoeing blade with the rotary tiller. Control was as high as 80% four weeks after treatment. The tiller plus hoeing blade outperformed the hoeing blade alone in some instances, likely because this combination better-disrupted weed root-soil contact (Figure 2).
Figure 1. On-farm study evaluating under-vine cultivator in Turner, OR in the spring of 2021.