Understanding Lawn Fertilizer Numbers

Today I am picking up with the series I started on DIY lawn care and understanding how much it costs. In the first post I talked about granular fertilizer cost comparisons and showed you that if you just look for the lowest price, you actually could end up paying more.

Today we are going to take a different approach and look at what’s actually in the bag and determine how that would impact the cost of an application.

In that first post I showed you a Milorganite alternative (a biosolid) called ProCare. This is Lowe’s answer to the MILO shortage. The analysis for the ProCare fertilizer is 4-3-0.

What Do The Numbers On The Bag Stand For?
When you see the 3 numbers on a bag of fertilizer, that is called its “analysis.” Those numbers appear on all lawn fertilizers and they indicate the amount of N-P-K (nitrogen, phosphorus, potassium) inside the bag. N-P-K are macronutrients.
For this fertilizer, 4-3-0 analysis means:

Nitrogen - 4%
Phosphorous - 3%
Potassium - 0%

When you see 3 numbers on a bag of fertilizer, those 3 numbers always represent N-P-K.

The bag of ProCare is 36lbs. When you see the 4% nitrogen, that means that 4% of everything in the bag is nitrogen. Since the bag is 36lbs that means that 1.44lbs of that bag are nitrogen.
36 x .04 = 1.44
We also know that 3% of the bag is phosphorous or 1.08 lbs.
36 x .03 = 1.08
There is some other stuff in this bag if you read the label, including iron and calcium.

The rest of the bag is other organic matter or “filler” materials. In the case of this particular fertilizer, known as a “biosolid,” the prills in the bag are what is left after microbes consume sewage and then get baked at high temps.

Those baked microbes have an analysis of 4-3-0 plus some iron and calcium. I will talk more about the sources of the nutrients in another post coming up. (organic/natural vs synthetic). For now, just know that this ProCare fertilizer is a natural fertilizer with an analysis of 4-3-0 and those numbers indicate percentages.
Application Standards
In the world of DIY lawn care, we have a standard we use whereby we talk about application amounts in terms of 1,000 sq ft increments. This is the standard unit of measurement that almost all lawn care products will use. That’s why you will see language such as “covers 15,000 sq ft” or “application rate 3lbs/1,000 sq ft” on bags of fertilizer.
You can see in this photo here, the Flagship fertilizer has an analysis of 24-0-6 and it covers 15,000 sq ft. You can do math or read the label further and you’ll see that the application rate is 3lbs/1,000 sq ft. That is telling you to apply 3lbs of Flagship fertilizer to each 1,000 sq ft area of your lawn.

In relation, go back up and look at the ProCare label where you see it covers 2,500 sq ft. It would take 6 bags of ProCare to cover the same amount of lawn space as 1 bag of Flagship.
We will get into that in more detail down below, but for now, as you move forward in your lawn care journey, get used to calculating your product details in relation to how many “1,000 sq ft areas” you have in your lawn.

Lawn Measuring - Learning Your Land

That is the standard unit of measurement - 1,000 sq ft - and that’s why it’s important to measure your lawn. That’s the first thing you need to do when starting your lawn care journey - measure your lawn.

In my yard care training course - Yard Care Bootcamp I go into this standard extensively and talk about measuring your lawn and learning your land.

I also have a video here you can view where I talk about measuring your lawn and creating a property map. Additionally, you can now measure your lawn right inside my lawn care app! Get the FREE app for Android here and Iphone here.
Once you measure your lawn, just think about the new information that opens up to you. If you measure your lawn and find that it’s 5,000 sq ft total, then you now know that a bag of fertilizer that covers 15,000 sq ft will actually get you 3 full applications (Flagship) and you also realize that a bag of fertilizer that only covers 2,500 sq ft will require 2 full bags just to get one application done (ProCare)

See how that works in understanding your budget against what you are spending?

We use the 1,000 sq ft standard for a lot of other things too - weed killers, fungicides, even buying a lawn mower, is based on knowing the size of your lawn and how many 1,000 sq ft areas you are caring for. Unlocking this one piece of data opens up a whole new level of understanding for your entire lawn care strategy even if you don’t realize it yet.

It’s one thing to just go and buy a bag of fert, throw it down and then hope for the best. That’s what most DIYers do and it’s just fine - the Scotts Company has built a very large business on this model.

But if you want to know a little more info about the “why” behind things, then that is when you start applying some math to the elements inside the bag and that starts by knowing your lawn size.
Now it’s time to dig a little deeper - deeper green that is!

Nitrogen Drives The Bus

When I set up my lawn programs, I center them around nitrogen. That is and always has been my approach. I care about the other elements that the lawn needs too, but for me, nitrogen is my starting point. This has worked for me, but more importantly, it’s worked for 10s of thousands of DIYers who have followed my strategies for well over a decade.

Nitrogen is what turns the grass green and that is what people who use my strategies want: a greener lawn. In my experience, a “good shot” of nitrogen that will turn your lawn green is going to be right around .75 lbs of nitrogen per 1,000 sq ft.

You can go lighter than that, and you can go heavier and you will still be ok, but for me, and what I do, you will find that I usually recommend nitrogen shots to be ¾ lbs per 1,000 sq ft and during growth periods, I like to push ¾ lbs/N/1,000 every 4-5 weeks.

Remember above how I told you that the ProCare Natural listed has a 4-3-0 analysis which means it’s 4% nitrogen? Just to review, that means that of the 36lbs of “stuff” in that bag, 4% of it is nitrogen.

So let’s look at the recommended application rate on that product and see just how much nitrogen it’s going to give us:
You can find out the “application rate” in a couple of different ways. One way is to read the label and in most cases, the rate will be listed which you can see here is 14.4 lbs per 1,000 sq ft.
That means you would spread 14.4 lbs of the fertilizer across each 1,000 sq ft area of your lawn.

Another way to get the application rate is to go back to the front of the bag and find 2 pieces of information.

Bag Weight

These two things will be listed on the front of every bag of lawn fertilizer you buy. In the case of ProCare we see the bag covers up to 2,500 sq ft (called the bag rate) and the weight of the bag is 36lbs.

Watch this math.
36/2.5 = 14.4

See what I did there?

The bag weighs 36 lbs and it can cover 2,500 sq ft.
That means that each 1,000 sq ft area would then get 14.4 lbs of product applied to it.
NOTE: This is where spreader settings come into play. Typically the spreader settings will deliver that application rate if you are to make your application in one single pass with a broadcast spreader.

Pounds on the Ground

Now we can start to understand how this application rate looks in relation to the nitrogen content because remember, “nitrogen drives the bus!”

All of this math is great but none of it matters if we are not getting enough nitrogen to show the biggest change in the color of the lawn.

You’ll remember that I typically recommend .75lbs of nitrogen per 1,000 sq ft of lawn area in my fertilizer recommendations. I recommend you give your lawn this ¾ lbs/N/1,000 abut every 4-5 weeks during growth periods. Let’s see what the ProCare is going to deliver should you choose to sling it:

Application Rate: 14.4lbs / 1,000 sq ft
Nitrogen Analysis: 4%
14.4 x .04 = .576
That means if you apply the recommended rate of the ProCare, you are going to be getting almost .6lbs of nitrogen per 1,000 sq ft.
So basically, a little over ½ lb of nitrogen per 1,000 sq ft.

That’s ok but it certainly isn’t the ¾ lbs/N/1,000 that I would be looking for.

Let’s compare that to the 24-0-6 Flagship fertilizer that we have on Yard Mastery.

Application rate: 3lbs/1,000 sq ft
Nitrogen Analysis: 24%
3 x .24 = .72
That’s very close to that ¾ lbs/N/1,000 that I am looking for! And of course it is, it’s my fertilizer lol

But what else can we learn from this?

First off is that you would be saving a TON of money buying the Flagship fertilizer if your goal was to get down a good shot of nitrogen. Check this out:
ProCare 4-3-0
Cost: $14
Coverage: 2,500 sq ft
Cost per 1,000: $5.60

Cost for a 5,000 sq ft lawn: $28 (2 bags)

Flagship 24-0-6
Cost: $55 (includes delivery)
Coverage: 15,000 sq ft
Cost per 1,000: $3.67

Cost for 5,000 sq ft lawn: $18.35 (still have enough left for two more apps)
That’s alot of math but I promise you, it’s not that difficult once you grasp it. If you are confused, go back and read this post again and get out a calculator and start messing with the numbers until it clicks for you.

Here are the basics in summary:
“Nitrogen Drives The Bus”

24-0-6 Flagship
Cost: $55
Bag Weight: 45 lbs
Coverage: 15,000 sq ft
Application Rate: 3 lbs/1,000 sq ft
Cost per 1,000 sq ft: $3.67
Cost for 5,000 sq ft Lawn: $18.35

Pounds on the Ground - Nitrogen : .72 lbs/1,000

ProCare 4-3-0
Cost: $14
Bag Weight: 45 lbs
Coverage: 2,500 sq ft
Cost per 1,000: $5.60
Cost for a 5,000 sq ft lawn: $28 (2 bags)

Pounds on the Ground - Nitrogen : .58 lbs/1,000

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