West Tier Factorial ©

The West Tier Factorial: This bloomtime photo clearly shows the training and floor management treatments of the experiment. Notice the difference in light interception between HRU training (10 rows on right) and GDC training (10 rows on left).

Dr. Nelson Shaulis, the distinguished Viticulturist, once said to me while discussing his West Tier experiment, "viticulture treatments that stimulate grapevine root growth and activity increase vine size while treatments that depress root growth and activity decrease vine size." Our discussion then turned to the topics of vine size, yield, brix, cane pruning weight, canopy density, microclimate, internal shading, etc. -- concepts for which he was more famous. Since vine size is one of the most limiting factors to Concord production in the Lake Erie region, his statement on root growth and activity is important.

The West Tier experiment is a factorial of floor management, nitrogen fertilization, rootstock, pruning, training, and shoot positioning. The first three factors have a direct effect on root function and the last three factors have an effect on the canopy and crop which in turn have an effect on roots.

Here is a brief review of the West Tier Factorial from the perspective of a Root Biologist/Viticulturist . . .

Floor Management (Sod vs. Cultivation)

Plants that grow in vineyard row centers, whether you consider them ground cover or weeds, compete with grapevines for water an nutrients. The rooting density of most weed populations is much higher than Concord grape roots; therefore, the weeds will have a competitive edge over grapes. In the West Tier, eliminating the competition with cultivation increases water and nutrient availability to Concord roots, resulting in more vegetative growth (vine size) greater retained nodes (because of balanced pruning), and higher yield.

It is important to note that subsequent floor management research by Bob Pool and Alan Lakso followed the same concept but recorded better results by eliminating the weed competition with herbicide instead of cultivation.

Nitrogen Fertilization (0, 50, or 100 pounds actual N)

When an essential plant nutrient (any essential plant nutrient) cannot be taken up by the plant in sufficient amounts because it is not present in the soil, it is unavailable in the soil, and/or its uptake is limited by insufficient root growth; fertilization with that nutrient may improve uptake. When a plant is not deficient in an essential plant nutrient, further addition of that nutrient to the soil solution will not improve growth.

These concepts are clearly illustrated in the West Tier with nitrogen fertilization. Fertilizing with 50 lb. of N improved vine size and yield over 0 lb. of N. However, fertilizing with 100 lb. of N did not increase vine size or yield of Concord over 50 lb. of N. In contrast, excessive nitrogen fertilization has the potential of promoting excessive vine growth which can lead to shading and lower juice soluble solids.

Rootstock (ownrooted vs. C.3309 rootstock)

In general, Concord vines grafted onto C.3309 rootstock have larger vine size than ownrooted vines. Interestingly, the Concord/C.3309 vines do not respond as dramatically to floor management and nitrogen fertilization as the ownrooted vines. Nelson Shaulis used C.3309 rootstock because it is resistant to phylloxera infection. However we are finding that the root distribution of C.3309 rootstock in the deep gravel soil of the Fredonia Lab also has a large effect on nutrient and water uptake. C.3309 roots grow much deeper than Concord roots and may tap into water and nutrients deeper in the soil profile.

One major caution with Concord/C.3309 vines is that this treatment can have water relations that are too good for Concord production! Unlimited water can lead to excessive vine size and berries pumped up with water (both leading to lower juice soluble solids because of shading and/or dilution at a comparable yield).

This illustrates the effect of root stimulating treatments on the vine size and yield of Concord grapevines.

Pruning (Balanced 30+10 vs. 60+10), Training (HRU vs. GDC), shoot positioning (yes/no)

Pruning, training, and shoot positioning have an effect on crop load and light interception. Assuming that vines have sufficient water and mineral nutrient relations, crop load and light interception affect carbohydrate assimilation and partitioning in the grapevine.

Balanced pruning adjusts the retained nodes to balance the vegetative and reproductive growth of the vine (if you will forgive my oversimplification). Less severe pruning favors reproductive growth and more severe pruning favors vegetative growth. Roots are part of the vegetative growth portion of that equation. Provided there is sufficient light interception (i.e. a full canopy of functional leaves), decreasing the crop load can partition more energy to root growth and activity. Therefore, it has the potential of increasing nutrient and water uptake.

Again assuming a full and functional canopy, GDC training increases light interception (carbohydrate assimilation) and has the potential of improving root growth (carbohydrate partitioning).

Shoot positioning in Concord vines decreases vegetative growth and can increase shading in large vines. Since the West Tier vines are balanced pruned, less vegetative growth leads to fewer retained nodes and lower yield.