In vineyards, competition from cover crops can be used to limit the exposure of vines to disease, a study by Penn State University says. In this way the use of herbicides is reduced
by Matteo Cavallito
The application of cover crops in vineyards can be a sustainable strategy for protecting plants and soil by providing essential ecosystem services, according to a study by Pennsylvania State University. The investigation, carried out with the support of the US Department of Agriculture and the Pennsylvania Wine Marketing Board, highlighted in particular how this practice allows growers to avoid the use of herbicides and protect the soil from heavy rains.
The role of cover crops
“If there are a lot of big leaves growing around clusters of grapes, it traps moisture and prevents wind flow, creating a microhabitat that promotes disease,” said Michela Centinari, Associate Professor of Viticulture at Penn State and co-author of the study with colleagues Suzanne M. Fleishman, David M. Eissenstat and Grant M. Hoffer, quoted in an article released by the Penn State website. Hence the researchers’ idea: to encourage competition by cover crops to limit the vegetative growth of vines.
This strategy has a number of side-effects, starting with lower yields. Under certain conditions, however, its use becomes convenient.
In particular, the research states, “at sites with high soil resources, reducing excessive vegetative growth is often considered beneficial, if the yield is not strongly penalized.”. In this context, in order to ensure the optimisation of cover crop services, it becomes necessary to evaluate the plant response over several years. Which is exactly what the authors have done.
For five years, says the article, the researchers monitored the cover crop at a vineyard managed by Penn State’s Russell E. Larson Agricultural Research Center. In this way, the study authors were able to observe the effects of the cover crop – the creeping red fescue (Festuca rubra L.), a very common type of grass – on grape production as well as on the growth of the plant’s leaves and roots.
“Overall, cover crop reduced grapevine vegetative growth between 13% and 30% across all years and with a trend of more substantial reductions in the first two years,” the research explains.
On the other hand, yield was reduced in three of the five years of observation between 9% and 25%, depending on the rootstock (the plant on which the portion of the branch where the shoots develop is welded). At the same time, the researchers found no relevant (or at least attributable to the herbaceous crop) alterations in the chemistry of the fruit.
A viable alternative to be tested over the years
The research, therefore, showed that in a young and relatively fertile vineyard, the combination of a suitable rootstock ( a low vigour one in this case) with a perennial cover crop under the vine was able to provide the essential ecosystem services. This has therefore proven to be a viable alternative to the most common practices involving the use of herbicides.
The effective combination of crops and rootstocks, the research points out, resulted in an improvement in the ratio of fruit to vegetative mass and an increase in the availability of phosphorus and water in the soil.
At the same time, this most likely implies a reduction in the maintenance costs of the vineyard itself. The results, the study specifies, will have to be further monitored over the next few years to assess, in particular, whether the competitive effect of the herbaceous species does not end up leading to an excessive reduction in nutritional levels, growth and vine yield.