16-0-0 Double Dark  6% Iron - Bio-Nite - Granular Lawn Fertilizer
16-0-0 Double Dark  6% Iron - Bio-Nite - Granular Lawn Fertilizer
16-0-0 Double Dark  6% Iron - Bio-Nite - Granular Lawn Fertilizer

16-0-0 Double Dark 6% Iron - Bio-Nite - Granular Lawn Fertilizer

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At MySoil® we do not produce or manufacture fertilizer products, but rather connect DIY’ers to vetted products developed by vendors specifically for the DIY market. 

16-0-0 Double Dark blend will do just what the name implies, make your lawn double dark green, It's really that simple. The 16-0-0 Double Dark contains no phosphorus or potassium, but 25% Slow-release nitrogen and a nice 6% Iron with other micronutrients. Use when your soil test just recommends nitrogen or when you want to give your lawn a little extra color!  This fertilizer is a "hybrid", containing synthetic nutrient components as well as a natural organic base component called Bio-Nite. The Bio-Nite component feeds soil microbes and assists in building soil health. Formulated specifically for DIYers.

  • One 45 lb bag covers up to15,000 sq ft
    • Low:   3.0 lbs/1000 sq ft covers 15,000 sq ft
    • Med:  4.0 lbs/1000 sq ft covers 11,250 sq ft
    • High:  5.0 lbs/1000 sq ft covers 9,000 sq ft
  • Analysis is 16-0-0 : N-P-K
  • Contains 6% Iron + Bio-Nite™
  • Contains micronutrients: magnesium, boron, copper, manganese, molybdenum, and zinc
  • Great for greening up the lawn without too much growth or when recommended by a soil test


Product Description:
Double Dark contains 6% iron. There are very few granular fertilizers available that have this much iron in them. Iron is the key to that dark blue-green color, but Double Dark also contains 16% nitrogen because the iron won't work if the lawn isn't actively growing.

The nitrogen in 16-0-0 Double Dark isn't over the top, it's just respectable at 16% and, 25% of that N is slow-release. You will get some green from the Nitrogen, but it's not going to cause too much top growth. The nitrogen is really just there to stimulate intake of the Iron and other soil nutrients.


For Warm-season turf will benefit from sustained “spoon-feeding” monthly in summer with this product.

Cool-season turf will benefit from added color without a strong surge from too much N.


All-Natural Bio-Nite™ in Every Bag!

Bio-Nite is a bio-solid filler added to every bag of 16-0-0 Double Dark. Bio-Nite is the same thing as Milorganite, but comes out of South Florida instead of Milwaukee. The included Bio-Nite is feeding microbes in the soil every time you apply!


Application Information:

You can apply 16-0-0 Double Dark when your soil test recommends or when you just need a little more color and growth. 16-0-0 Double Dark can be used on the following grasses:

Cool Season Lawns - Kentucky Bluegrass, Turf Type Tall Fescue (all fescues), Ryegrass.
Warm Season Lawns - Bermuda, St Augustine, Zoysia, Centipede, Bahia.


A 45 lb bag covers up to 15,000 square feet

Application  Details

Apply at 3-5 lbs per 1,000 square feet of lawn area

Apply every 4-6 weeks

Can be applied at any time during the growing season for both cool and warm-season lawns

Water-In  Instructions

Apply to a dry lawn, and water into turf within the first 48 hours with 1/4" of rainfall or irrigation

Sweep excess off sidewalks and driveways to avoid staining


Product Resources:

  • Label: 16-0-0 Double Dark PDF Label
  • Package Includes: 1 - 45 lb. bag
  • Storage: Store in dry conditions away from moisture. Can be stored for up to 2 years.
Shipping costs

Included for most states within the U.S.

NO P.O. Boxes

$9.95 for CA, WA, ID, and OR

State Restrictions

Alaska (AK), and Hawaii (HI)


Yes, free stickers with this item

Typical Delivery Time

4 - 7 business days

Product Type


Cancel | Return | Exchange

All sales are final, no cancellations, returns, or exchanges


Customer Reviews

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Customer Reviews
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Dark green

This product worked great for my lawn. Turned it dark green. I’m not a lawn scientist, so I don’t know what else it did but it sure made it look good.

Herb H.

Stained my sidewalk and driveway worse than any product I haver used

Second time I used the product. First time no issues. Second time it caused hundreds of rust stains on my sidewalk and driveway. Even stained my neighbor's sidewalk due to too much iron in the fertilizer. Even caused deep brown stains in my zoyisa lawn. I will never use it again. Costing me hundreds and a lot of labor hours to get the stains removed. Not sure if the lawn will recover.

Rodney R.
United States United States


Grass didn’t seem to get that double dark or dark green. Maybe it’s the type of grass I use and I live in the PNW

Eldon R.
United States United States

Good Stuff

I used this on my St Augustine grass and it worked great.

United States United States

Good but could be great

I have used the test twice and it has helped but only on the p h because I understand P H but it seems too complicated to figure out each thing that isn't in optimal condition. I need to know at what point do I need to react and what do I need to do. ie optimum is 3 to 5 and mine is 8 do I need to do anything What do I need to do I have some results in red why I understand I got the results and they seem well done but for $30 I was hoping for some simple suggestions this report and no details on how to change or if it needs attention is little help for me. I will not use again. The p h is in black why