Mineral Nutrition

Essential plant nutrients are grouped by the amounts in which they are needed, as outlined in NCERT Class 11, Chapter 12 (Mineral Nutrition). Macronutrients are elements required in relatively large quantities, present in plant tissues at concentrations exceeding ten millimoles per kilogram of dry matter; this group includes carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium and sulphur. Micronutrients, by contrast, are needed in trace amounts, below ten millimoles per kilogram of dry matter, and include iron, manganese, copper, zinc, boron, molybdenum and chlorine. A beneficial element is one that improves growth in certain plants but is not essential for all, such as sodium or silicon, so it does not fit the quantitative definition asked here. A non-essential element is not required for the plant's life cycle at all and is therefore irrelevant to this classification. The numerical threshold of ten millimoles per kilogram is the defining criterion. A sanity check confirms the categorisation: nutrients used in building bulk structures like proteins and nucleic acids are needed in large amounts, which is exactly why they fall in the macronutrient class.