Annual Under-Vine Cover Crops Mitigate Vine Vigor in a Mature and Vigorous Cabernet franc Vineyard

Abstract

Excessive vine vegetative growth in wet, cool climates increases management costs and compromises grape quality. The standard practice of bare soil under vines exacerbates the vigor problem. This study examined the ability of under-vine cover crops to mitigate excessive vigor in a mature vineyard. A three-year study was conducted in a mature Cabernet Franc vineyard in Ovid, NY. Under-vine cover crops of chicory (CHI), tall fescue (FES), tillage radish (TR), and alfalfa (ALF) along with natural vegetation (NV) were established annually since 2014 to compare with a control of glyphosate maintained bare soil (GLY). Pruning weight was reduced 64% by CHI, and 54% by FES and TR compared to GLY, respectively, in 2015. Primary and lateral shoot growth were suppressed by CHI in 2016. Fruiting zone leaf layer number was reduced by all of the under-vine cover crops in 2015 and by CHI and FES in 2016. Yield per vine was not reduced by any of the under-vine cover crops in any year of the study. Under-vine cover crops had little impact on harvest parameters including soluble solids, titratable acidity, pH and yeast assimilable nitrogen. Soil properties including aggregate stability, microbial respiration rate, and carbon mineralizability were improved by some cover crops. Although NV, FES, TR showed little and ALF showed neutral effect on vine growth and yield components, CHI effectively alleviated mature vine vigor without reducing yield in cool climate. Since water or nutrient competition alone did not fully explain the vine vigor mitigation effect of under-vine cover crops, other mechanisms such as microbial or allelopathic effects of under-vine cover crops should be examined in the future.