The Effects Of Poly-Coated Urea On Sweet Corn Production


If you are in the market for a new, more efficient way to apply nitrogen to your sweet corn crop, poly-coated urea may be the answer.

A study conducted by Ron Goldy, Senior Extension Educator and Vegetable Specialist at Michigan State University, evaluated the effects of a single application of poly-coated urea compared to split applications of regular urea.

Below, Goldy explains his research process and the benefits of poly-coated urea on sweet corn.

American Vegetable Grower (AVG): What is poly-coated urea? How does it differ from regular urea?

Goldy: The active ingredient is the same, except poly-coated urea is coated with a water soluble polymer, which makes for a slower release to the system.

One of the problems with urea is that it volatilizes and leaches quickly. The growing conditions and the temperature have to be right; otherwise, a lot of the urea you apply can get lost.

Instead of having this big boost of nitrogen at the beginning and tapering off, poly-coated urea provides a more uniform release rate and the plant is able to utilize it much better.

Poly-coated urea doesn’t change the rate of absorption, it changes the amount of nitrogen available to the plant at any given time.


AVG: Can you provide a brief summary of your research process?

Goldy: We used two extremes, one where we applied 150 pounds of nitrogen as plain urea at three separate times during the typical program for growers, and the other extreme was 150 pounds of nitrogen as poly-coated urea applied at planting. Both treatments applied the same nitrogen rate.

The other treatments were variations of that, where I would apply 25 pounds of nitrogen as straight urea with 125 pounds of nitrogen as poly-coated urea, for example, prior to planting. We also applied regular urea at planting and then followed it up with the poly-coated when the plants were 18 inches tall. Some growers were asking what would happen if they gave it a boost at the beginning and then applied poly-coated later on.

Also, both boron and sulfur were worked into the soil prior to planting. We have found our sandy soils to be low in both, so we add them yearly to bring them up to acceptable levels. Boron is needed for kernel set, and sulfur is a micronutrient that is lacking in our soils. Both are necessary elements for plant growth.

AVG: What application methods did you use, and did it make a difference in the results?

Goldy: We broadcasted the poly-coated urea, and the first time we broadcasted it before planting we were able to lightly disk it in. When the plants were growing, we broadcasted it and watered [the poly-coated urea] in by timing it with an irrigation event. No matter how we applied it, we received similar results.

AVG: What plant qualities you were looking to affect with this research?

Goldy: We evaluated plant height, ear weight, length, and diameter. The bottom line was yield and ear quality as measured by ear size. The goal was to determine if one application of 150 pounds of nitrogen per acre as poly-coated urea would provide similar yields as split applications of regular urea.

AVG: What were your final results?

Goldy: We found that 150 pounds of nitrogen per acre application of poly-coated urea gave us similar yield and quality as 150 pounds per acre nitrogen applied as straight urea, or split applications of urea plus poly-coated urea equaling 150 pounds per acre nitrogen.

AVG: What was the cost difference in applications? Would you recommend the use of poly-coated urea to growers?

Goldy: The cost of the product is higher for poly-coated urea. In this case, even though we applied it once, when you figure in labor and equipment costs of additional applications, it still came in at a higher cost than the multiple applications of straight urea. However, there is a benefit of being able to apply it once and forget about it. It’s much nicer to have a one-and-done application; you don’t go through with a second or third broadcast.

I believe this is something growers should consider. They should research the least expensive sources of the products as the price may vary some with supplier and quantity purchased.

Next, we are also looking at applying lower rates of poly-coated urea, between 75 to 150 pounds nitrogen per acre. It’s possible you might buy less of the poly-coated urea because you’re not using so much and it might not take 150 pounds of nitrogen as poly-coated urea to get the same yield response as 150 pounds of nitrogen as straight urea.

What are some major takeaway and action points for growers from your research?

  1. One application of poly-coated urea can take the place of split applications of regular urea.
  2. Poly-coated urea is slightly more expensive than regular urea.
  3. Poly-coated urea provides growers with a “one-and-done” approach to nitrogen fertilization, allowing growers to concentrate on other activities.
  4. Poly-coated urea is safer for the environment since it releases nitrogen at a rate more suitable for plant uptake.