A Cardinal number represents an equivalence class of sets between which there is a bijection (one-to-one correspondence). It is the number of elements in any member of the equivalence class. An Ordinal number represents an equivalence class of well-ordered sets between which there is an order-preserving bijection. It is the number of elements in any member of the equivalence class. The difference is only in whether the sets are ordered.
It is the basis for protein manufacture in plants and plays a major part in photosynthesis. For lawns, shrubs and leafy houseplants, a nitrogen-rich fertilizer is the best choice. When reading a fertilizer package, nitrogen will be the first in a series of numbers appearing with dashes between them. For example, a formula of 10-0-0 is a nitrogen-only fertilizer.
The main nitrogen-based straight fertilizer is ammonia or its solutions. Ammonium nitrate (NH 4 NO 3) is also widely used. About 15M tons were produced in 1981. Urea is another popular source of nitrogen, having the advantage that it is a solid and non-explosive, unlike ammonia and ammonium nitrate, respectively.n addition to their providing the nutrition to plants, excess fertilizers can be poisonous to the same plant. Competitive with the uptake by plants is the degradation or loss of the fertilizer. Microbes degrade many fertilizers, e.g., by immobilization or oxidation.