Cover crops influence on soil N availability and grapevine N status, and its relationship with biogenic

Abstract

The type of soil management, tillage versus cover crops, can modify the soil microbial activity, which causes the mineralization of organic N to NO3–N and, therefore, may change the soil NO3–N availability in vineyard. The soil NO3–N availability could influence the grapevine nutritional status and the grape amino acid composition. Amino acids are precursors of biogenic amines, compounds mainly formed during the malolactic fermentation. Biogenic amines have negative effects on consumer health and on the wine organoleptic quality. The objective was to study if the effect of conventional tillage and two different cover crops (leguminous versus gramineous) on grapevine N status, could relate to the wine biogenic amines composition. The study was carried out in a vineyard of A.O.C. Rioja, planted in 1999 with cv. Tempranillo (Vitis vinifera L.) grafted on 110-Richter rootstock (2,849 vines ha-1). Vines were trained on a double Cordon Royat. The treatments were: tillage (T), cover crop of barley (B) (Hordeum vulgare L.), and cover crop of clover (C) (Trifolium resupinatum L.). Each treatment consisted of three repetitions. Soil NO3–N was monitored at 0-15 and 15-45 cm soil depth at budbreak, bloom, fruit set, veraison and postharvest during four years (2009, 2010, 2011 and 2012). Soil NO3–N was extracted with 2 M KCl and determined by colorimetry. Grapevine N content was analyzed in leaf tissues (blade and petiole) sampled at bloom and veraison. Nitrogen content in leaves was determined by dry and instantaneous combustion. In each repetition, 15-20 grapevines were harvested. Wines were elaborated following the traditional method used in A.O.C. Rioja for red wines. The biogenic amines content in wines (histamine, methylamine, ethylamine, tyramine, phenylethylamine, putrescine, isoamylamine and cadaverine) was determined by HPLC. The results showed that the barley cover crop reduced soil NO3–N availability and clover cover crop increased it. Leaf tissues N content, at bloom of third year decreased with the barley treatment in both blade and petiole. In 2012, N content, in both leaf tissues at bloom, was greater with the clover treatment than with both the tillage and the barley treatments. Content of N in leaf tissues indicated that changes in the soil NO3–N affected levels of N in vines. In the fourth season, total content of biogenic amines in wine decreased in the barley treatment respect to both tillage and clover treatments. Correlations were observed between methylamine and the petiole N content at bloom, histamine and ethylamine respect to both leaf tissues at veraison and putrescine with blade at veraison. Finally, total biogenic amines was positively correlated with both leaf tissues at bloom and at veraison. In conclusion, the concentration of biogenic amines in wines can be affected by the N nutritional status of the grapevines, provoked by changes in the soil NO3–N availability as a result of the implanted cover crops effect.