Soil nutrients that are essential to plants are categorized into three broad groupings: (1) Macronutrients: carbon (C), hydrogen (H), oxygen (O) – supplied by air and water – nitrogen (N), phosphorus (P), potassium (K). (2) Secondary Nutrients: calcium (Ca), magnesium (Mg), sulfur (S). (3) Micronutrients: boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), zinc (Zn). Regardless of category, all these elements are critical to crop production.
The only variance is the relative demand level of plants for the given nutrient. Macronutrient requirements of plants are relatively high; whereas, the secondary nutrients are often added to soils incidentally with lime, manure, precipitation, etc. and usually do not limit crop growth as frequently as N, P, or K deficiencies. Soil micronutrients, on the other hand, are needed by plants in small quantities. This does not diminish their importance in crop production. This paper will focus on the major micronutrients and their role in crop production.