Quick-Release vs. Slow-Release Nitrogen Fertilizers

The Basics

• The words quick and slow give away the biggest difference between these types of fertilizers. Quick-release fertilizers are water-soluble and release high amounts of nitrogen in a very short amount of time, beginning immediately after application. Slow-release fertilizer, on the other hand, isn't water soluble. These fertilizers release nitrogen over a period of two months or more. Application often consists of spreading with a broadcast spreader at a rate of anywhere between 1/2 and 2 cups per 100 square feet, depending on the organic matter content in the soil and the type of nitrogen fertilizer.

Ingredients

• Quick-release fertilizers are always synthetic products, while slow-release fertilizers may be either natural or synthetic, or a mixture of both. Quick-release nitrogen fertilizers are commonly ammonium nitrate, ammonium sulfate or urea. Slow-release nitrogen fertilizers include sulfur-coated urea, Isobutylidene diurea and organic fertilizers such as composted manures. In short, quick-release fertilizers are never acceptable for organic gardening, if you're going that route.

Quicker's Always Better, Right?

• Terms like quick and fast often seem like no-brainers due to them being fast-acting. When you want a result, in this case greening up your plants, you often don't want to wait for it. But therein lies the problem. These fertilizers release nitrogen almost too fast, which can cause severe damage to your lawn, veggies or ornamental plants. The most common problem in plants associated with quick-release fertilizer is root burning. The high amounts of nitrogen that are released at application can quickly burn roots, sometimes to the point that the plant cannot recover. Don't be too alarmed, however; proper application helps prevent burning. A good way to think of quick-release fertilizers, as so wittily put by Thurston County, Washington's Department of Public Health and Social Services, is by comparing them to junk food: they give off quick bursts of energy to your plants, but wear off quickly.

Other Considerations

• Another problem with quick-release nitrogen is that plants can only absorb so much nitrogen at a time, meaning the rest is left in the soil. Unfortunately, what's left is quickly leached into water. One bonus of quick-release fertilizer is that it's often cheaper -- considerably so, in some cases -- than slow-release fertilizer. However, you also need to apply them more frequently.