Alternative sources of nitrogen
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
Purchasing ammonium nitrate fertilizer is becoming difficult for small nursery and Christmas tree growers. Many fertilizer outlets no longer stock ammonium nitrate in bags due to liability and regulatory concerns. Ammonium nitrate is generally available for bulk purchasing, but many smaller scale operations that don’t have equipment to handle bulk fertilizers are left looking for an alternative.
Nitrogen is available in a wide variety of fertilizer forms. There are couple of key points to keep in mind where looking for N alternatives. First, remember various N sources have different effects on soil pH. Ammonium sources, over the long-run, tend to acidify the soil reducing pH. In some cases this effect is desired. Conifer growers often use ammonium sulfate, which is strongly acidifying, as a primary N source for acid-loving trees such as firs. Some nitrate-based sources of N such as calcium nitrate and sodium nitrate tend to raise soil pH over time. Potassium nitrate has a neutral effect of pH.
Alterative N sources can add additional nutrients that you may or may not need for your crop. If a soil test indicates that your crop needs phosphorus, diammonium phosphate may be a good choice. Likewise if potassium is low, then potassium nitrate might be the fertilizer of choice.
Urea is another popular source of N. Like ammonium nitrate, it’s relatively cheap. Remember that urea can volatilize at warm temperatures, so it is best to apply when the weather is cool and wet or else it should be incorporated into the surface of the soil.
With continually rising fuel prices, growers may also want to re-consider controlled release fertilizers (CRF’s). Field nursery and Christmas tree growers have usually dismissed CRF’s as too expensive for field application. The cost and times savings of two or three additional passes over the field for mid-season fertilization, however, may change the economics of these decisions.
Dr. Cregg's work is funded in part by MSU's AgBioResearch.