A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism''s metabolism which must be taken in from its environment. Nutrients are the substances that enrich the body. Methods for nutrient intake vary, with animals and protists consuming foods that are digested by an internal digestive system, but most plants ingest nutrients directly from the soil through their roots or from the atmosphere. Some plants, like carnivorous plants, externally digest nutrients from animals, before ingesting them. Organic nutrients include carbohydrates, fats, proteins (or their building blocks, amino acids), and vitamins. Inorganic chemical compounds such as dietary minerals, water, and oxygen may also be considered nutrients. A nutrient is essential to an organism if it cannot be synthesized by the organism in sufficient quantities and must be obtained from an external source. Nutrients needed in large quantities are called macro- and micro-nutrients are required in only small quantities. This book covers the occurrence of deficiencies of the plant macro- and micro-nutrients, their causes, effects and treatment in different crops.