"The
difference in nitrogen fertilizers" Craig Paskvan, Paskvan
Consulting
August, 2000
I would like to briefly touch on the differences in nitrogen fertilizers. Mainly I want to touch on ammonium sulfate and urea as they are the most commonly used in the golf course business. In most of the recommendations that I make, my first choice is going to be ammonium sulfate. There are a number of reasons for that. First of all, most of the soils that I deal with are calcareous sands that have a fairly high pH. The higher the pH, the more calcium and phosphorus are going to be tied up and unavailable to the plant. In order to make those available to the plants, plus other minerals that are tied up due to the pH, we need to be using acid based fertilizers, or fertilizers that will help lower the pH of the soil around the root hair. Ammonium sulfate is a nitrogen source that will help us do that. Secondly, because ammonium sulfate carries a positive charge, it can cling to the negative charge of the soil colloid, acting more like a slow release type nitrogen; and because it needs to be broken down before the plants can utilize it, we are feeding the microbes in the soil. Remember, that the microbes are the intermediaries between the fertilizer and the plants. The healthier we can keep the soil and the microbes, the healthier plants we can raise. Also, by using ammonium sulfate we are adding sulfur to the soil in the S04 form. Plants need sulfur at about the same level as they need phosphorus, and by using ammonium sulfate we're not only adding sulfur to the plant, but it is in a form that the plant can use immediately. It does not need to be broken down. Also, ammonium sulfate has a very good energy rating.
Urea, on the other hand, is also a synthetic type of nitrogen, which is in the same form as animal urine. It is one of the cheapest forms of nitrogen to produce, which is one of the reasons it is pushed so much. There is a good profit margin with it. One of the pluses in using urea is that it promotes what I call green growth, but the energy levels of urea are only fair. That may be due in part to the fact that when urea breaks down, it gives off formaldehyde residues. These residues will have a negative impact on soil microbes. Also, urea is subject to volatilization if it is not watered in quickly. Another reason I am not partial to urea is that it may tend to dry out soils. Now before you think that I am totally against urea, I am not. Urea is a very good foliar feed. Plants can use urea nitrogen with little internal energy usage when it is foliar applied.
These are just some very brief reasons why I prefer the use of ammonium sulfate to urea.
Craig
Paskvan,
Founder
Paskvan Consulting
Soil Tests • Water Quality Tests • Environmental Consulting Services
• Balanced Soil and Plant Nutrition • Monitoring and Analytical Services
for Golf Courses
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