The growth and yield achieved by your grapevines each year depends heavily on the Nitrogen (N) levels in the vineyard. While some amount of nitrogen is typically needed each year, the best way to determine what quantity to apply to a mature vineyard is by taking a petiole test. Soil samples should be taken of new vineyards to determine first year application needs. Too little nitrogen often results in limited shoot growth and canopy development leading to reduced yields while, too much nitrogen promotes too much vegetation causing shading, and poor fruit and bud development. Ammonium Sulfate is one method of nitrogen application that can be used in the vineyards.