Abstract
Plant and soil analyses are complementary tools for the diagnosis and prognosis (prediction) of crop nutrient status and environmental quality. Their use depends on well-established relationships between nutrient concentration (in plants or soils) and plant growth/yield or environmental quality. Based on a calibrated relationship, nutrient concentrations are categorized into deficient, adequate, and toxic ranges. From these relationships, the critical concentration range is defined, corresponding usually to concentrations required to obtain 90% or 95% of maximal growth/yield. In addition, use can be made of visual plant symptoms to recognize nutritional disorders. Fertilizer recommendations are often based on plant or soil analysis results. Critical deficiency ranges are dependent on plant age, plant part, concentrations of other nutrients, as well as on environmental factors. Plant analysis can be used to either diagnose existing disorders in plants or predict future nutrient limitations based on various calibration relationships. Soil tests are complementary to plant tests and are used primarily to predict future nutrient limitations.