Academic literature on the topic 'Interveinal chlorosis'

The fertility of a soil refers to its nutrient supplying power. It is one of the most important soil factors affecting vineyard productivity, which is measured in tonnes of grapes per ha (or sometimes tons per acre). For viticulture, soil physical prop­erties, notably structure, aeration, and drainage are also very important determi­nants of productivity, as discussed in chapters 3, 6, and 7. Because vines are grown in permanent rows, and there are many cultural operations, soil physical prob­lems are often more difficult to ameliorate than problems of soil fertility. Soil fertility is assessed either by observing the condition of vines growing on a particular soil or by measuring the nutrient supplying power of the soil itself. The assessment should include recommendations on how to correct any problems identified. Thus, assessment of soil fertility can be made in two parts: 1. Diagnosis of nutrient deficiencies or excesses. The aim here is to identify which nutrients are deficient or in excess and the degree of deficiency or excess. An excess of a nutrient, which may create an imbalance with other nutrients, often leads to a nutrient toxicity. 2. Estimation of nutrient requirements. The goal here is to estimate how much of a limiting nutrient is required to achieve optimum growth or how to remedy a toxicity problem. Nutrient amendments can be made with fertilizers, manures, and composts, or by growing cover crops that include legumes. Visual symptoms are the signs that indicate a deficiency or excess of one or more essential elements in a plant. In the case of grapevines, such symptoms include chlorosis, stunted growth of shoots, necrosis of leaf margins, irregular fruit set, and small berries. Chlorosis is a generic term for leaf yellowing due to loss of chlorophyll. N deficiency typically causes an overall chlorosis of the leaves, but in other cases chlorosis occurs between the leaf veins (interveinal chlorosis). Some examples of visual symptoms are given in table 5.1 and figure 5.1.