soil nutrients, elements (see minerals) and ions occurring in the soil which are taken up by plant root systems. Soils which are rich in nutrients are often termed fertile, but such soils do not usually produce good-quality wine (see soil fertility). The amounts of nutrients that are available to the vine depend on the soil’s mineralogy, the amount and nature of organic matter, and also the soil ph. Soils with a long history of cover crops have high levels of surface organic matter and are often rich in nitrogen. However, grass and cereal cover crops compete with vines for nitrogen, so nitrogen is not as available to the vine as when the cover crop contains legume species. Soils in old vineyards, especially if clean cultivated, are often relatively impoverished of organic matter and may have high levels of available copper as a result of repeated fungicide application. Many nutrients including nitrogen and phosphorus, for example, are less available in acid soils (see soil acidity). Others such as iron, manganese, copper, and zinc are less available in alkaline soils. Nutrient deficiencies are diagnosed by symptoms on the vines, or by plant and soil tests, and can be remedied by applying fertilizers and manures.