The Concord Floor Management Conundrum

Are cover crops the answer for Concord vineyards in the Lake Erie AVA?

There has been a lot of interest recently on the use of cover crops in commercial Concord production in the Lake Erie AVA as a way to improve soil health and vineyard nutrition. The competition for water by cover crops, however, needs to be addressed before adoption.

What do we know…

• We have established that as vine size (or vine capacity) increases, so does yield potential.

• Increasing vines size is directly influenced by water and nutrient uptake and indirectly influenced by crop load.

• Concord roots are relatively shallow rooted compared to many other rootstock options.

• The majority of commercial Concord vineyards are ownrooted and not irrigated.

Cover crops out-compete ownrooted Concord vines for available soil moisture. Dr. Bob Pool and Dr. Alan Lakso of Cornell conducted several Concord floor management and root biology studies in the 1990s which demonstrated the competitive effect of covers on Concord vine size and yield. In general, cover crops, with higher rooting density than Concord, led to smaller vines with less yield.

Cultivating row middles, terminating the cover crops with herbicide, or applying a thick layer of mulch conserved soil moisture and led to larger vines and higher yield. Problem solved…except that treatments like cultivation and repeated herbicide use, the most common treatment in the Lake Erie region, work against the principles for building soil health – which are maximizing continuous living roots, increasing biodiversity, minimizing soil disturbance, and maximizing soil cover. Straw mulch is an option but it needs to be thick enough to choke out weeds and it can be expensive to apply over large acres.

Like in many other areas, compromise seems to be the answer to balancing vine water management, improving soil health, and minimizing costs. Concord water demands are directly related to the amount of active leaf area, a function of both vine size and time of the season. Water competition should be minimized from about two-weeks pre-bloom to veraison and this becomes more important in vineyards with larger vine size. Dr. Pool demonstrated this by growing annual rye grass and terminating it around bloom, which led to an extended weed free time during the middle of the growing season.

As we explore further cover crop use in Concord vineyards, it will be important to look for options which are terminated or are naturally not competitive from early-June to mid-August but increase diversity and soil cover for the other 10 months of the year.

(Of course, there are other water management options which include different rootstock selections and irrigation that I will talk about in future posts.)