Molybdenum (Mo) is one of the six “minor” chemical elements required by green plants, which are essential for normal growth of plants. Of these six minor elements, Mo is needed in smaller quantities than any of the others. As little as 50 grams of Mo per hectare will satisfy the needs of most crops. Mo, which is often present in farmyard manure, in seeds or other planting material such as tubers and corms and as impurities in some artificial fertilisers, is needed by plants for chemical changes associated with nitrogen nutrition. Where the plant has insufficient Mo, the nitrates accumulate in the leaves and the plant cannot use them to make proteins and hence becomes stunted.