Fertilizer is used to enrich the growing medium of plants with essential nutrients. It differs from compost in that compost is used as soil or mixed into soil, while fertilizer is added solely as a source of nutrients. Fertilizer can be made with organic waste and enriched with chemicals like Ammonia (for Nitrogen). The purpose of fertilizer is to allow plants to reach essential elements more easily, or to supplement nutrients absent from certain soils.
|ppm, dry wt.||%, dry wt.|
|hydrogen||63,000||6.3||In water and carbohydrates|
Average elemental composition of corn tissue (silage). From Troeh, Frederick and L. M. Thompson. 1993. Soils and soil fertility. Oxford University Press. New York.
This table is for corn. Exact composition for plants will vary, but will generally be in similar proportions.
The most important fertilizer is nitrogen(N), followed by potassium (K) and phosphorus(P). Calcium(Ca) and magnesium(Mg) can be supplied by limestone, if it is found on Mars. Silicon is the most abundant element on Mars after oxygen.