YM 16-0-0 Double Dark (with 6% Iron) and Bio-Nite™ - Granular Lawn Fertilizer

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New for 2021 ~ "Double Dark" blend will do just what the name implies: make your lawn double dark green. It's really that simple - green and more green.

Double Dark is meant for those of you who are inclined to apply fertilizer every 30 days. Most programs recommend an application of lawn fertilizer every 4-6 weeks or so. But there are those of you who apply every 30 days on the dot and some of you push it even closer together than that. This product is for you.

It will green up the lawn but won't flush it with too much growth.

Why Double Dark?

First off, let's just point out: it's 6% iron. There are very few granular fertilizers available that have this much iron in them. We all know that iron is the key to that dark blue-green color, but...

... Double Dark also contains 16% nitrogen because one thing that so many people forget is that iron won't work if the lawn isn't actively growing.

Think about it: the lawn has to be growing in order to take in nutrients and what element stimulates growth? Answer: Nitrogen

Better Than Ironite 

Search around and you will hear people who say, "I was using Ironite but after a while it just stopped working." That is because there is no nitrogen in that product to keep things growing. The two work together and that is the secret to the Double Dark.

The nitrogen we put in Double Dark Blend isn't over the top - it's just respectable at 16% and, one quarter of that N is slow release.

You will get some green from the N too, but it's not going to smack your lawn in the face and make it flush out a bunch of top growth. The nitrogen is really just there to stimulate intake of the iron and other included micronutrients. (Double Dark has boron, copper, manganese and zinc too.)

Bio-Nite Smells Like Success

As with ALL Yard Mastery custom blends, we also spiked the Double Dark with Bio-Nite, a Milorganite clone from South Florida that brings the smell of success and feeds those microbes.

When To Apply Double Dark

You can apply Double Dark Blend whenever you want an extra layer of dark green color without pushing a ton of growth. All grass types, anytime. Also great for anyone on a "low N" program. Apply in between your regular fertilizer applications if you just feel like you want to sling some fert!

Centipede and Bahia: this is an excellent summer fertilizer for you too. It won't push a lot of extra growth but will deliver good color.

Application Rates

We recommend 3lbs/1,000 which should be all you need to see results within 6-7 days. Keep in mind, at this rate, you are only applying .46lbs/N per 1,000 sq ft but you are also getting quite a bit of iron and that is what makes this fertilizer unique.


We partnered with Sunniland to blend this fertilizer for us which guarantees a high quality, consistent prill that is easy to spread from any spreader.


Analysis: 16-0-0 plus 6% iron!

  • 45 lb bag covers 15,000 sq ft

Best times to apply:

Double Dark 16-0-0 plus 6% iron can be applied year round anytime you want to double down on the blue-green color in your lawn. It’s really good for any grass type in summer. Cool season lawns can benefit from added color without a strong surge from too much N and warm season lawns can benefit from sustained “spoon feeding” monthly in summer with this product.

Cool Season Lawns - Bluegrass, Fescue, Ryegrass (Best Application Mid Spring, Late Spring and Summer)

Warm Season Lawns - Bermuda, St Augustine, Zoysia, Centipede, Bahia (Best Application Late Spring and Summer)

Application Instructions:

Application rate is 3 lbs of product per 1,000 sq ft of lawn area. Apply to a dry lawn, sweep excess off sidewalks and driveways to avoid staining. Application should be watered in within 48 hours with ¼” or rainfall or irrigation.