Nitrogen has a major impact on vineyard vigour, and potentially on wine quality. Nitrogen is essential for vine growth and is one of the three major elements, along with potassium and phosphorus, needed most for plant growth. It is an important component of proteins, and also of chlorophyll. The most common symptoms of nitrogen deficiency, which can be expected on sandy soils low in organic matter, are reduced vigour and uniformly pale green or yellow leaves. Soil and plant tests can be used as a guide to the use of nitrogen fertilizers.