#13- N-P-K: Understanding fertilizer bags, micro and macro nutrients, nitrogen and granular fertilizer

Look at any bag of fertilizer and you will see three large numbers on the front of the bag: N-P-K. What does it mean? How much to apply? What is in fertilizer? Do I apply slow or quick release? What are micronutrients? Find the answers to these questions and more in this episode.


Hey, hey, what is up, everyone? This is Ete with another episode of EcoLawn Science. Today, we're going to talk about fertilizer on your lawn. So we're going to talk about granular fertilizer, so the little pellets that you apply with a push spreader, a riding spreader, a chest pack spreader, a hand spreader, any kind of spreader. And I want to talk a little bit about what's in that and what's in the bag. So if you've ever seen a bag of fertilizer, you'll notice there's always three numbers on it. It could be 21-3-10. It could be 24-8-10, 32-5-7, 46-0-0, 33-4-7. The combination is endless, and all that means is... it's, the bag is taking...what they're telling you is the macro nutrients. 

So because of the way we've installed our lawns, ripped out good topsoil, fertilized, the damage that we cause our lawns, um, they don't naturally take care of themselves. They need a little extra to stay green. Now some might, with good water and a little bit of fertilizing, replenish nutrients. But most people need some additives, some fertilizer. 

And so the bag, the first number is an “N.” It's a nitrogen. Nitrogen is your key nutrient in plant growth. So of all the macro and micro lawn nutrients that are in the soil, and then the ones we need to add in, the N, the nitrogen is usually the one most talked about. The nitrogen promotes rapid growth, leaf development, chlorophyll formation, and protein synthesis. So basically, when you put that nitrogen on it, you're looking at, you're really feeding the top half. You're not going below the soil. You're feeding the grass, the blades, and you're causing that thing to shoot high. So if anyone has a lawn they have to mow every three or four days, it's probably because they're over there adding, too much N, too much nitrogen. And that's the nutrient that most people hear about the most. 

And so it gets, unfortunately, gets too much attention. There are downsides to overapplying N. Absolutely. You can deplete the soil of microorganisms. You can injure organisms, especially if a lot of the N, or the nutrients are carried to the soil by salt, so you can have too much salt in the soil. You can off-balance the ecosystem in the soil and the root zone. If you cause too much top growth, you can actually throw that whole lawn area off balance, which can lead to fungus and massive insect problems. And we do see that quite a bit in Salt Lake. A lot of the major fungal issues that we're having right now with NRS especially, a lot of that's caused by over-fertilizing with nitrogen. People will just put it down. And that's the problem is because it is so good at greening up things. People just throw down. More nitrogen. More nitrogen. You'll hear it all the time, but whoa, step back, breathe, you know. Take a look at it. Let's look at this from a balanced perspective. It's...too much of anything is not a good thing. So that's nitrogen. 

The second letter or the number that you'll find on the bag, it will usually have a “P” on it and that stands for phosphorus. Phosphorus plays a key role in early root growth, so, you know, younger, earlier on in the plant cycle’s life, it hastens maturity, and it stimulates blooming and also helps with seed formation. So when you're establishing a new lawn...Now, some areas in the States, phosphorus is banned. You can't apply it. Some areas you can't apply it all. You have to have a fertilizer that has zero there. So 21-0-5 right, no phosphorous. Or some areas you can have, um, phosphorous can only be applied during certain months. So I know back east, down south, there are some areas you can't put it in after September. And a lot of that has to do with how it stays in the soil and the run-off, especially if you're near lakes, rivers, that type of thing. 

And then the third nutrient that we have for our Macros is potassium, which increases the resistance to drought and disease, and it also is a big component in root development. So I love potassium, especially in the fall. It'll help with stress, you know, drought stress, tolerance. Just get those roots, you know, growing deep and growing down. 

So that's the three numbers on the front. The other part of the picture that people often...So most people go for the N. That's all they ever care about. More nitrogen equals greener lawn, but they're not finishing the equation because I would say equals, you know, or too much nitrogen equals imbalance, which equals, you know, fungal/insect problems. You know, these types of things. 

So there are also micronutrients. Those are the macros. But a lot of times the problem with your lawn or soil, it could have a lack of micros, and a lot of times they get overlooked. People don't pay attention to them. So what are micronutrients? So the ones..there are quite a few. I think it really depends on where you are, what your soil looks like. That's why I recommend getting a test, because a lot of times it just comes down to the...there are more than five, but the main, you know, five or six. 

So you're looking at sulphur. Okay, so to produce nitrogen, the plants need the sulfur. It plays a huge role in forming proteins, you know, so that’s sulfur. Then you've got copper, Cu, which is huge for producing chlorophyll and activating enzymes. It's just an overall important part of health, and it can help to like, fortify and build really strong cell walls and thicker. You have Manganese, which can help protect plants from disease. It also can help plants ingest the nitrogen and kind of finish off that photosynthesis process. And so, if you have a deficiency in Manganese, which you’ll have in more like sandy, high peat soils, you will see like a spotted or discoloration on the leaves. So you want to make sure that's dialed in. And there's also magnesium, which helps fortify, again, turfgrass for the winter, plays a huge role in producing chlorophyll and processing nitrogen, phosphates, iron. So there's magnesium. And then, of course, there's iron, which as mentioned, plays a massive role in chlorophyll, and it actually is one of the best ways to green up a lawn without using the nitrogen. Because nitrogen, it'll make that plant, the grass, grow, grow, grow. You're cutting...excessive leaf growth. And now I've already talked about some of the problems with that. Well iron can also get you a nice green lawn without that leaf growth. And so anyway, those are just some of the few micronutrients. 

So you've got your macro–It's just like a body, right–you’ve got your macros and you've got your micros and the healthy system is a combination, the right amount of all of those dialed in. So how do you find it? You get a soil sample. You test for your macro and micronutrients, and then you make your adjustments. You make a plan based on what you find. 

So as you look at that bag and you see the three main numbers we've talked about, the nitrogen, the N, the N-P-K–nitrogen, phosphorus, potassium. Whatever that number is, so if the number is 32, is the N number, that means that bag is 32% of the fertilizer is nitrogen. You know, if it's 32-3-7, the 3% is the phosphorus, 7% is the potassium of that bag? So what you have to do is you have to understand how much do I put down. How do I figure this out?

 And so what you want to do, the first thing you want to do is you want to go to look at your state. So, like in Utah, you go to USU extension, they'll actually tell you, if you have a bluegrass lawn or–because you could have a different type, you could have a fescue lawn and it’s going to be different–but I would...the starting point is with the state. So you go to the state. They may recommend, you know, 4 lbs of N per 1000 per year. 

Now in lawn care “per 1000” is kind of the minimum. That's the standard of area that we talk about. All the products are…they're labeled how to apply per 1000. That means 1000 square feet. So that means if you had 100 feet by 10 feet patch, um, you know, and you have a total of 1000 square feet that's what they're talking about. So if you went to the state site and they say they may say–or if you did a soil sample–and it says, hey, I want you to put down 4 lbs of N per 1000 per year, right. What you would do is, let's say you are going to do four applications a year. You would then divide the N needed, which is, um, 4 lbs into four applications. So you have to make sure each of those treatments, you're putting down a pound of nitrogen per 1000 square feet. 

There's a little more involved, but that's the overall concept, and I find a lot of people get in trouble because they ignore it. They just say, hey, more nitrogen green. But really, if you overfeed that you're going to cause more issues and it's gonna come back to really bite you. So follow the labels. 

Understand how much do I need of this nutrient per 1000 square foot per year. And then how much do I want to give it each time? A pound of N per 1000 per treatment, if you were doing four, that's a lot of fertilizer. People who do six treatments a year they might break it down to 1/2 a pound, so each of those treatments of the six will have 1/2 a pound or whatever the math is, of nitrogen in there. So the next thing to look at is what type, I mean, are we talking? So nitrogen can come in all kinds of forms and it can get real...we're not going to dive too deep into that on this one. That's going to be a whole other episode, but your standards are usually like a urea, an ammonium nitrate, ammonium sulfate, a sulfur-coated urea, things like that. Those are the more standard ones. 

And then you need to also understand, is it a slow release or quick release? And the difference there is basically your quick release, if you apply that, it's just going to release right into the soil. So let's say it's 100% quick release. It's going to just go, and it's going to break down immediately, where your slow release or controlled releases, there's different ways they create those. Some are wrapped with a...they’re coated, you know, with a sulfur coat so they break down over time. And some I've seen, they have, like, a triple coating where it takes time, moisture level, ambient temperature, ground temperature to break it down so they could last for 6 weeks. So that means you don't have to come back for another four weeks to do the treatment. So that's a really simplistic approach. 

You could go really deep a lot more into the nitrogen sources, where they come from, what benefits the lawn. You could go deep into, well if I put these nutrients on my lawn is my lawn going to be able to utilize them. But for this one, I really wanted to just get you thinking about when you grab that bag of fertilizer, know what those are. Know the macros, know the micros, and then know what you need. Do the soil sample. Check out my podcast on soil samples. I think for 50 or 60 bucks, you could have a soil sample and get real results of a breakdown that will tell you everything about your soil and where to start. You know, don't just randomly start somewhere unless you have a guide, a good path. 

And so that's N-P-K. That's macro/micro nutrients. A little bit about nitrogen fertilizer in a nutshell. I hope this was helpful to you. Have a great day and I’ll see you on the next episode.

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