A: Slow-release fertilizers release their nutrients gradually, over time, reducing the chance of "overdosing" your lawn, and our precious waterways.
Plants fed a timed-release fertilizer benefit from a consistent supply of the elements they need throughout their growth phase. Unlike quick-release or fast-acting fertilizers, slow-release fertilizers aren't water soluble. This quality, plus the fact that nutrients are released in useful amounts, means they aren't washed away in stormwater runoff.
Slow-release fertilizers are usually more expensive than fast-acting products. However, they require less application so the small increase in upfront investment can be cost-effective. Additionally, they are less likely to "burn" your yard, they help establish sustainable growth and they are an important way that homeowners can reduce water pollution.
Look for products with 50% slow-release (or water insoluble) nitrogen, and then apply this product at the recommended rate twice a year, in the spring and fall.
A: Fertilizer labels always list nitrogen first among the three numbers on the bag. They also are required to list how much of the nitrogen is in water-insoluble, or slow release, form.
A: Example A
If you have a bag of 10-10-10 fertilizer, with the 3 numbers representing Nitrogen, Phosphorous and Potassium in order, and 5% of the nitrogen is in water-insoluble form, here is what you get:
5 ÷ 10 = .5 x 100 = 50
This bag contains 50% slow release nitrogen.
If you have a bag of 16-2-6 fertilizer, with 4% in water-insoluble form, here is what you get:
4 ÷ 16 = .25 x 100= 25
This bag contains 25% slow release nitrogen.