Florida Landscape Doctor

Why use a slow release Nitrogen fertilizer

Nitrogen is the nutrient plants need most. There is not enough readily available in the soil for the plant and that is why we need to supply it. No matter what source of nitrogen you apply – synthetic or organic – most ends up as plant-available nitrate through a process called nitrification. However, the rate of nitrification (that is, the rate at which nitrogen becomes available to the plants or the rate of nitrogen release) varies. For example, most of the available nitrogen from quick release sources is gone within 4 to 6 weeks after application. Slow release fertilizers can provide nitrogen all season long.

Slow release fertilizers have some advantages over inorganic salt fertilizers. Although inorganic salts begin supplying nitrogen immediately after application, the results are fast growth and a quick green-up they don’t have longevity. There will also be a possibility of turf burn with the quick release fertilizers. The other problem is they often provide more nitrates than the turf can use.

Let’s discuss what makes the nitrogen a slow release. What helps it Hang in their longer ?

It is due to a Polymer coating on the fertilizer. To get a long term controlled release the fertilizer needs to have this coating. There are two types of coatings, one is a polymer coating sometimes called reactive –layer coated urea and the other is a polymer-coated-sulfur coated urea. Coating urea with polymer means that nitrogen release will last 8-16 weeks rather than 2 to 6 weeks as with uncoated urea. Have you ever wondered how your neighbor got such a green lawn so quickly but why it didn’t last long. That is due to the quick release. With sulfur coated urea fertilizers the coating creates a predictable release profile. What causes the release? Water. Nitrogen becomes available from polymer-coated urea as water diffuses through the coating and dissolves the urea particle. Nitrogen then diffuses through the coating by osmosis. It then continues to diffuse into the soil until the urea is gone. These fertilizers release nitrogen faster with high temperatures. In warmer climates, manufacturers increase the coating thickness to slow the diffusion.

Natural organic fertilizers were once the only available fertilizer. When synthetic processes were developed, organics fell out of favor. Now they are making a come-back. Various organic materials such as sewage sludge, feather meal, animal waste, etc., are marketed today as organic fertilizers. Typically, 95 percent of the nitrogen in these materials is tied up in the organic form. About 5 percent is in the ammonium and nitrate forms. Nitrogen release relies on microbial decomposition, so nitrogen availability depends on warm moist weather which we have in Florida. There are people today that prefer the old cow manure from the pasture to help them with their gardens. It just takes longer to do it’s job of releasing the available nutrients. That is why society hires out their work They want immediate results, sometimes a quick green, and there are some who prefer the slow release for long term results. My suggestion would be to use a 16-4-8, 25 percent SCU, 3 percent iron fertilizer for your turf. You should see about a 90 day climb for Greening and from 90 to 120 day drop. At 120 days you’ll be ready to fertilize again. So prime time to fertilize will be March July and November. Each 120 days apart. That seems to be the best program for year round care. This will be your 12 month program. It has worked for me and it should work for you.

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