The document discusses plant nutrients and their classification. It explains that there are 17 essential plant nutrients that can be classified as basic, macro or micro nutrients. Basic nutrients include carbon, hydrogen and oxygen obtained from air and water. Macro nutrients include primary nutrients like nitrogen, phosphorus and potassium supplied through fertilizers, and secondary nutrients like calcium, magnesium and sulfur. Micro nutrients, also called minor or trace elements, include iron, manganese, zinc, copper, boron, chlorine, molybdenum and nickel. The document also discusses the functions and deficiency symptoms of various major nutrients.