Soil nutrient availability under Cover Crops: Effects on vines, must, and wine in a Tempranillo Vineyard

© 2015 by the American Society for Enology and Viticulture. All rights reserved. Cover crops can compete with vines for soil nutrients and thus can affect grapevine development and must and wine quality. The objective of this study was to evaluate the influence of two different cover crops on the availability of soil N, P, K, and Mg and on grapevine nutritional status, vigor, yield, and must and wine quality. The experiment was carried out in a cv. Tempranillo vineyard in La Rioja, Spain, using three treatments: a gramineous cover crop (barley), a leguminous cover crop (clover), and conventional tillage. Soil nitrate evolution and P, K, and Mg were determined, and total biomass and nutrient content of cover crops were measured. We also assessed leaf nutrient content, vine vigor, yield, and must and wine quality. Uptake of P, K, and Mg by cover crops did not reduce the soil availability of those nutrients and did not affect their concentrations in grapevines. The barley cover crop reduced soil N availability from the first year onward and led to decreased leaf N and vine vigor in the third year. Increased polyphenol content and color intensity were observed in the barley treatment in the fourth year, and these changes were more significant in must than in wine. The clover treatment increased soil N availability in years 2 through 4 and led to increased leaf N content in the third and fourth years. The use of barley as a cover crop could be a viable alternative for reducing soil N and improving must and wine quality; however, these effects required time to develop after introduction of the cover crop.