Nitrogen (N), phosphorus (P) and potassium (K) are referred to as primary or macronutrients. This is because they are required by the plants in large amounts relative to other nutrients and they are the nutrients most likely to be found limiting plant growth and development.
Use of micronutrient fertilizer materials should only be undertaken with very clear objectives in mind and with a knowledge of previously successful rates of application.
Nitrogen promotes rapid growth, chlorophyll formation and protein synthesis.
Phosphorus stimulates early root growth. Hastens maturity. Stimulates blooming and aids seed formation.
Potassium increases resistance to drought and disease. Increases stalk and straw strength. Increases quality of grain and seed.
The fertilizer guaranteed analysis refers to how much of an element is in the material based on percentage of weight. All fertilizers are labeled with 3 numbers which give the percentage of weight of total nitrogen (N), phosphorus (P2O5) and water-soluble potassium (K2O). N-P-K
If we have a 50 lb bag of 10-10-10, there are 5 pounds of N, 5 pounds of P2O5 and 5 pounds of K2O. The other 35 pounds of fertilizer material is filler or the carrier material of the fertilizer. The filler or carrier helps to evenly spread the fertilizer and avoids burning plants with too much fertilizer.
The best fertilizer grade to use depends on the current soil test levels in your field and what nutrients are most needed to ensure that no nutrient will limit production. Sometimes only nitrogen is required, but only a good soil testing program can provide you with that information. Availability of fertilizer materials and costs are always a consideration in planning your fertility program.
Nitrogen fertilizer materials
| Material | Analysis | Physical form | Comments |
| Urea | 46-0-0 | Solid (prills, granules) | Highly volatile. Best used when chances for rainfall are high. |
| Ammonium nitrate | 34-0-0 | Solid (prills or granules) | Low volatility. Great nitrogen option during dry periods. |
| UAN solutions | (28-32)-0-0 | liquid | Normally 33-35% urea and 45 to 47% is ammonium nitrate; weighs about 11.1 pounds per gallon |
| Ammonium sulfate | 21-0-0 + 24 S | Solid (granules) | Used primarily as an acidifying fertilizer or source of sulfur |
Phosphorus fertilizer materials
| Material | Analysis | Form | Comments |
| Diammonium phosphate | 18-46-0 | Solid, granule | |
| Monoammonium phosphate | 11-48-0 | Solid, granule | |
| Triple superphosphate | 0-46-0 | Solid, granule |
Potassium fertilizer materials
| Material | Analysis | Physical form | Comments |
| Potassium chloride, Potash | 0-0-60 | Soil, granule | Bermudagrass can be a luxury consumer of potassium. Split applications. |
Vanessa Corriher-Olson
Professor, Forage Extension Specialist
Soil & Crop Sciences
Texas A&M AgriLife Extension, Overton,TX
903-834-6191