Berry nitrogen status altered by cover cropping: Effects on berry hormone dynamics, growth and amino acid composition of Pinot Noir

The influence of altered nitrogen (N) content, caused by cover crop, on Pinot Noir berry quality was studied. Treatments included two levels of cover cropping and clean-cultivation. Berry N-content was reduced by grass cover crop competition, with the highest reductions of N at the early stage of berry formation and at the commercial harvest stage. Growth regulators, trans-zeatin and indole-3-acetic acid, and berry growth were influenced by the changes in N-status at different stages of berry formation. The total amino acid content of berries at harvest decreased with cover cropping, while the proline to arginine ratio and assimilable amino acids content improved compared to the berries from clean-cultivated vines. Our data indicate that early stage berry development is influenced by N-status but finally it results in an improved amino acid composition for yeast fermentation in mature berries. At the same time, sugar and pigment contents were not negatively influenced by cover crop-induced changes in berry N-status.