Although N, P and K are all important nutrients, more attention is given to nitrogen because it is needed in the largest quantity and will give the greatest response. Applying nitrogen during the playing season will significantly improve turf quality, growth and recovery. Water soluble nitrogen sources provide rapid response within days or a week (depending on temperature) and will typically last about 2-6 weeks. Slow release or controlled release nitrogen sources offer an extend period of nutrition and can last 8-12 weeks and some even as long as 20 weeks.
Natural organic nitrogen sources come from plant and animal by-products or waste products. They are typically lower in nutrients, have little burn or leaching potential and require warm moist soils for availability. The rate of nitrogen release from organic sources does differ. Research from North Carolina State University found that over a 10 week period, Nature Safe (turkey manure and feathers) released 70% of its total nitrogen, Milorganite (bio-solids) 60% and Bion (hog waste) 20%. Products containing proteins (meat, blood, feathers, fish meal, corn gluten meal) release more nitrogen than previously digested sources such as bio-solids and animal wastes.
Characteristics of common turfgrass nitrogen sources
| Fertilizer Source | Nitrogen Content % | Leaching Potential1 | Burn Potential2 | Low Temp Response3 |
Residual Effect4 |
|---|---|---|---|---|---|
| Inorganic* | |||||
| Ammonium sulfate | 21 | high | high | rapid | short |
| Organic – Natural | |||||
| Bio-solids | 6 | very low | very low | very low | long |
| Manures | 3-10 | very low | very low | very low | long |
| Natural products | 3-12 | low-very low | very low | low-very low | mod-long |
| Organic – Synthetic | |||||
| Urea | 45-46 | high | high | rapid | short |
| Sulfur coated urea | 22-37 | low | low | moderate | moderate |
| IBDU | 31 | mod-low | low | moderate | moderate |
| Methylene ureas | 38 | low | low | very low | mod-long |
| Urea formaldehydes | 38 | mod-low | low | low | long |
* Ammonium nitrate and Calcium nitrate.
1 Leaching potential – likelihood of the fertilizer moving beyond the root zone due to its solubility.
2 Burn potential – likelihood of turf injury due to the salt concentration of the fertilizer.
3 Low temperature response – the ability of the fertilizer to have an effect under low temperature (50°- 60°, for example in the spring when early green up is desired.
4 Residual effect – estimates how long the fertilizer effect will last. For example, water soluble (quick release) fertilizers are short termed lasting between 2-8 weeks whereas slow release fertilizers may last up to 4 months or more.