Three examples of leguminous plant species being tested as cover crops here in local Niagara vineyards. From left: Trifolium incarnatum (crimson clover), Trifolium repens (white clover) and Melilotus officinalis (yellow sweet clover) (Photos: Kasia Zgurzynski)
Grapevines are not the only plants at work in a typical vineyard. Growers often incorporate additional species of plants in between and (less often in Canada) under the rows of vines as a way to boost growing conditions and potentially improve berry yield. These additional cultivated plants are called cover crops. Cover crops are not typically harvested, but rather serve to enhance the growing environment. Since plants provide a multitude of functions in nature and form the foundation of healthy ecosystems, it should come as no surprise that cover crops can be a useful vineyard management tool. Some examples of environmental enhancement that can be achieved by cover cropping are improved water infiltration, decreased soil runoff and erosion, weed control or the promotion of beneficial insects.
Cover crops can include various species of legumes (e.g., clover, vetch), forbs (e.g., chicory, oilseed radish) or grasses (e.g., fescue, timothy grass). Most legume species develop a reciprocal relationship with bacteria in the soil. These bacteria are beneficial and help capture the nitrogen and transform it to a form that can be absorbed by plants, making this key nutrient biologically available for the cash crop. Many grasses work as a kind of natural mulch, protecting the soil from drying out and suppressing the growth of weeds. Flowering plants with long and tough roots can break up the compaction in the soil, making it easier for water and oxygen to infiltrate deeply throughout the rooting zone, and drawing up water and nutrients from deep within the soil.
Sometimes, the true benefits of cover crops occur when they are turned back into the soil, providing the organic matter and nutrients necessary to maintain soil health. Cover crops can also be an important nectar and food source for beneficial insects, such as parasitic wasps that can control leafhoppers. That being said, depending on the species and where or when they are planted, cover crops may actually compete with the cash crop, introduce disease or impede wind flow between rows, so careful selection is important for the system to perform optimally. With climate change and the possibility of more climate variability, such as droughts and heavy rainfall, the presence of cover crops can help buffer the impacts of soil runoff or drought-induced soil cracking.
Overall, cover crops have the potential to be a relatively inexpensive and effective strategy for improving the health of the vineyard from the ground up. A plant does not have to be a cash crop to perform a service for the vineyard. These crops can also help integrate the vineyards more holistically into the surrounding landscape. The ecological services provided by cover crops are substantial even beyond the vineyard, as well, allowing vineyard owners to improve their own crops while also providing benefits to nearby growers and the surrounding ecosystem in the process.
This blog section will be ongoing throughout the duration of the project with bi-weekly updates provided by Liette Vasseur, Heather VanVolkenburg, Kasia Zgurzynski, Habib Ben Kalifa, and Diana Tosato (see research team). We will be providing research activity updates as well as informative pieces that delve into agricultural concepts and important global issues as they relate to agricultural sustainability and climate change. Stay tuned for regular updates!