Tuesday, 27 March 2018

Measuring Putting Green Infiltration Rates

In my last post I discussed how too much aerification might be a bad thing and wondered if more is better or if there is an ideal amount of compaction that we can maintain to maximize soil health and help us reduce the inputs that we currently require to maintain our putting greens. Inputs like sand, fertilizer, tines, fungicide and water.

I then shared how my greens have never performed better based on some anecdotal observations.

Yesterday I decided that if I was going to try and aerifiy less or not at all that I would need to measure the things that aerification is supposed to manage so that I can track their change over time. Simply not doing something without knowing that it's working is simply a dumb thing to do.

As usual, there were a ton of products that I needed to buy to figure out this kind of hokus pokus but then I remembered that I'm not doing super precise science here. I want to get a general idea of how my greens perform and relate that to my observations on how they actually perform and meet my expectations for my course's specific needs.

I have always measured organic matter when I soil test so I don't have to do anything different here.

To measure the percolation rate you can buy all kinds of fancy tools to measure how fast water moves through the soil but I decided to do it on the cheap.

I used an old cup cutter blade and marked a line 6cm up from the bottom. This is how far I drive it into the green. I then fill it with water up to the bottom of the top ring and start a timer. I come back, record the time and how far the water has dropped. This gives me the infiltration rate in mm/hr.

It was raining so hard I needed to cover the top of the old cup cutter blade to prevent it from filling back up!
Is this method perfect? Not even close. Typically you would want a double ring tester where the larger outer ring is also filled with water but not measured. This reduces lateral water flow below the cup cutter blade. For my testing my soils were at or above field capacity (36%VMC) so I wasn't too worried about it. You could always hammer the cup in deeper to a point below the majority of the roots (for me this is 6cm) and forget about the infiltration rate below that point. 

You should also use a constant time to measure the infiltration rate because the rate can vary from the first few minutes as the soil saturates. Again, I'm not too worried about being super precise here. I just want to know if my greens drain good.

I have only found drain pipe in one of our greens. Guess which one? Regardless, they all drain better than is needed.

So how fast should the greens drain? According to this blog post by the STRI we should aim for drainage at least 15-25mm/hr. If you find a green with issues, ask yourself if the grass is bad because of it, then do further testing to see if it's an isolated issue or widespread. You can test various depths to see if it's a surface issue or an issue that needs to be addressed with drainage or deep tine aerification. I think you will find quite a bit of variation from one green to another and even across a single greens as the topography and distance from drain line changes. All we are trying to do here is look for issues and negative changes over time. If we find issues we can them make informed decisions about them and if there are no issues we can do nothing!

As you can see in the above chart, All my greens drain more than adequately despite hardly aerifiying them in the past years. I really wish I had data from years ago to compare because I have a hunch that they drain better today then any time in the past. I also wonder if they will improve with less aerification or get worse. The only way to know is to wait and see!

It will be interesting to see how these numbers change over time especially following a wetting agent application coming next week.

I have 4 old cup cutter blades so I can do the testing on a rotation. To do 12 greens it only took me 1 hour to test this so I will be testing this much more often in the coming months and years. It's a super easy test to do and if it can reduce the amount of aerification required, then it will more than pay for the effort required to do the testing.

I also started measuring soil bulk density. We want to ensure that the soil isn't too compact that we limit root growth. Maybe we can use wetting agents in the winter to move water through a compacted soil, but roots still need physical space to grow.
Measuring bulk density

To measure bulk density I also used an old cup cutter blade. I measured the cross section, calculated the area of the opening and then determined the depth I would have to drive the cutter blade to measure both 500cm^3 and 1000cm^3. 

I measured my cup cutter blade to have a diameter of 105mm. As we all know the area of a circle is Area = π r^2. Our radius is 52.5mm so the cross sectional area of our cup cutter is 8654mm^2 or about 86cm^2. To get the depth for a 500cm^3 cylinder we divide the volume by the circle cross section to get 5.8cm. Simple double that to get 1000cm^3 depth.

So we want to find out the density of the soil in grams/cm^3. This is our bulk density. 

To do this first weigh your cup cutter blade. Then hammer it into the soil to the 500cm^3 depth and measure the combined mass of the cup cutter blade and the wet soil withing the blade. Make sure the bottom of the cup cutter is full of soil and it isn't sticking out at all.

Subtract the cup cutter mass from the total mass to get the mass of just the wet soil.

Ok great, but there's a problem. The soil moisture content will vary and soil moisture has mass. To figure out what the soil moisture weights take a paper cut. Weigh it, then add a sample of soil to the cup and weight it again. Now we can figure out the mass of a small sample of wet soil. Microwave the wet sample until it is completely dry. I like to stirr the sample to let the moisture leave it quicker. We now can compare the mass of the wet sample to the dry sample. This will give us a percentage. Typically this is about 80% for my soils. Every sample will be slightly different. Multiply this percentage by the mass of the total 500cm^3 sample to get the dried mass then divide this by 500 to get the bulk density.

Depending on where you read, upper limits will fall anywhere from 1.6-1.8g/cm^3 with ideal limits around 1.25-1.35. I'm not too concerned with having minimum bulk density and more concerned with ensuring that it's not too high. 

Again, this isn't super precise, but it's good enough for our purposes. If you want more precision you can pay some companies a lot of money to do it for you.

As can be seen, my greens are all within tolerable limits. I'm not as concerned about the absolute values I measured, but more so in the change over time. As is, the greens perform better than expected so who is anyone to say that the numbers I got are bad?

The reason I am measuring this is to confirm that I don't need to aerify for drainage purposes. Most of the research about rolling and disease has found that infiltration rates weren't negatively impacted by double rolling daily so that I good to know for disease management. So if we can keep good drainage and optimize the pore spaces in the top few cm with rolling then maybe we can have the best of both worlds. If we measure the infiltration rates we can eliminate the guesswork and be confident that not aerifiying won't end in disaster. It can also confirm that aerification is warranted and make it much easier to justify this disruptive practice to golfers and management. If you don't measure this stuff you are simply guessing. 

If you like my blog and want to support what I do you can support me on Patreon or paypal. Thanks!

Sunday, 25 March 2018

Does Aerification Make Disease Worse?

Have you ever noticed a disease outbreak immediately following aerification?

I'm pretty sure most people have and this is why it is common practice to spray a fungicide before aerifying. Why does this happen?

I always blamed the disease outbreak on the mechanical stress we put the grass under. I also noticed that the abrasive practices used to drag the sand into the aeration holes would spread the disease like crazy.

Fusarium Spread from verticutting after aerification

Niels Dokkuma from the Koninklijke Nederlandse Golf Federatie visited my course in February of 2017 to see what I was doing to reduce the pesticide use on my golf course because the Netherlands are facing an almost complete ban on pesticides in 2020 so they need to learn whatever they can to avoid disaster.

He asked me a seemingly simple question. "Do you think aerification makes disease worse?"

Of course I agreed with him and went into discussion about how we spread the disease around and the mechanical stress that goes on etc. We pretty much left it at that but ever since that meeting I have been thinking a lot about this. 

Does aerification cause disease?

Does the physical act of increasing macropores in the soil make disease worse?

I know you're thinking this guy is nuts! Aerification is nothing but good, right? Aerification makes disease less bad, right?

Lets forget the pain in the ass that aerification is. Broken equipment, bumpy greens, huge expense  loss of revenue, and poa seed brought to the surface. Lets forget about the obvious downside of aerification and think a bit about how else it could be hurting our operation.

Check out the following video where Dr. Thom Nikolai discusses the "most significant discovery of his research career." If this is the most important discovery of his research career I wonder what the most important discovery of his not-research career is? 

The research that he and his associates did on rolling and dollar spot is some of the most interesting research in the world of turfgrass management in my opinion. In the following video clip he discusses why he thinks rolling reduces dollar spot.

Cool, so rolling reduces dollar spot. What about other diseases?

A few years ago I discovered that rolling reduces fusarium patch!

So wait, if rolling reduces major diseases like dollar spot and fusarium patch wouldn't that suggest that compaction (or compression of the top mat layer) reduces disease and not aerification? Isn't rolling the exact opposite of aerification?

We all see the disease following aerification, see the results that compacting or compressing the soil can have on disease then say that aerification reduces disease!

Sounds a bit backwards to me! Sounds like a lame justification to do a practice that none of us like doing too. It's required to manage organic matter, infiltration rates and disease.


Maybe if the soils have been allowed to get to a point of neglect aerification will help but I think that with the tools and knowledge that a typical superintendent has available, we should be able to forget about the blanket aerification practices that are so common in our industry.

We've all heard of the general recommendations for aerification. Anywhere from 10%-20% surface disruption to ensure we don't run into trouble. This is probably a great general recommendation but it doesn't take your specific situation into account and this is one of the reasons I hate generalized agronomic recommendations. Every course is different. Different climate, different grass, different construction, different amount of traffic, and different budget.

If we are measuring clippings and only applying fertilizer to make the grass grow faster when required we should be able to make better use of the nutrients release from the soil organic matter and therefore use up that organic matter instead of continuously add to it. Add to this topdressing as required to keep the organic matter in check as determined by regular soil testing we should be able to eliminate the need for core aerification to remove excess organic matter. If we can be more precise with our fertilizer applications and growth rates we should have less waste and therefore less need for corrective maintenance practices.

What about infiltration? Surely aerification helps with infiltration! Yes, we've all seen the videos of an aerifier running over a puddle on a putting green and watched the water disappear almost instantly. I've always done this and even left the holes open during the winter to help aid in the drainage only to find that a few weeks following aerification the greens would puddle and we would be back to square one.

This winter I decided to try something new. I tried aerifying less aggressively and decided to use a penetrant (wetting agents, what's the difference?) through the winter. I don't have any quantitative data on this yet but what I can say with almost certainty is that our 30 year old greens have never drained better!

Our 4th green is severely sloped towards a sand trap and for the 17 years I have been here the sand trap would wash out every time it rained. This February we had a rain event that dropped over 100mm of rain in less than 24 hours.

The typical situation on our 4th green. This as the only time this winter we had a washout due to frozen soils.
So I went out to repair the trap in the morning to find that it wasn't washed out literally for the first time in 17 years! The bottom of the trap was full of water because it just rained 100mm and we don't aerify or spray wetting agents in the traps (maybe we should?).

This observation suggested to me that the rain went down into the soil instead of running across the surface and into this sand trap. All winter this has happened except for during the snow melt where the putting green soil was frozen solid and therefore not able to drain properly. Knowing if drainage is good is now very easy. If that trap washes out, I need to improve drainage. If it doesn't wash out, drainage is within tolerable levels and better than any time before 2018 in the club's history! No fancy tools needed although I am going to look into getting a way to quantify infiltration rates better.

So has aerification helped my greens drain better in the past? Not from what I've seen. Maybe it will get worse with no aerification so I will watch this in the future to make sure that they continue to drain as expected.

I think a lot of our issues with water infiltration come down to hydrophobic soils and I wonder if aerification makes this worse as well. When we aerify the greens we create these awesome holes for the water to flow down. Water is lazy so it always takes the path of least resistance and this can be called preferential flow in soils. If all the water is flowing down these few channels what is happening to the water and the soil surrounding these holes?

We have all seen the nice green holes following aerification and I wonder if it is that the grass in the holes is healthier or if the grass beside the holes is suffering because it is getting none of the water and gas exchange because of preferential flow. If we only disrupt 10-20% of the surface does the other 80-90% suffer?
Testing soil bulk density. Is the grass greener in the aeration holes or is the grass less green because of the aeration holes?
It's a really easy thing to try. Spray a penetrant on your greens in the winter and see if drainage improves. I think you will see that you get better drainage than ever before which makes me wonder why we would need to aerify to improve drainage if it only improves things for a short time and not even in a significant way?

The video below by Pace Turf shows how this phenominon can impact soils that are high in salts.

When it comes to hydrophobic soils I wonder if aerification makes it worse by drying out the soils surrounding the holes. In the winter time we don't notice the hydrophobic areas because et rates are low and precipitation is high but as soon as it warms up we see the same localized dry spots in the same location year after year.

What if we don't create preferential flow opportunities and just use penetrants to uniformly wet the soil all winter long. Will that help our localized dry spot issues in the summer? I've heard some talk of this in Scotland and I think there might be something to this idea. Bottom line, my greens have never been drier in the winter or drained better.

So what about aerification makes disease worse? In Nikolai's rolling research they found elevated levels of beneficial bacteria in the soil as a result of the rolling. It wasn't dew removal, it was the soil biology that they think were making the difference. It also appears that a more compressed soil favors bacteria which could compete with the fungi that cause all our problems.

So I think we need to focus on when it comes to soil aerification is to determine what is the optimum compression or compaction and work to keep our soils within tolerable limits.

The look of the profile continues to improve despite less aerification than ever before.
Maybe this is why most people see so little success with compost teas and bio-amendments. If you add these beneficial organisms to an environment that isn't ideal for them, they simply die. Hey Rob Wilke, do your soils ever dry down up there? Maybe the success Rob sees with compost and wood has a lot to do with almost constantly saturated soils in one of the rainiest places on earth. Wet, slightly compacted soil is ideal for bacteria that compete with the fungal pathogens..... Maybe too much air is a bad thing?

I'm over aerification. Instead, I have started measuring the physical properties of my putting greens and will monitor them over time to see if they change or fall outside of tolerable limits. I will try and avoid issues with compaction, excessive organic matter buildup and drainage without poking holes but will still keep aerification as a tool in case some areas run into trouble. I am currently measuring soil bulk density, infiltration rates and organic matter content. By tracking this over time on my HUD I should be able to make better decisions about when and how I aerify my greens, if at all.

Maybe we can find out what the ideal soil properties are for healthy soils and stop the ideas of more is better when it comes to aerification because the way I see it, more is definitely not better. I think a lot of our reliance on aerification comes from not measuring our soil properties and simply guessing too much. Maybe we can aerify less, and improve conditions?

Or maybe I'm completely insane......stay tuned to find out!

If you like my blog and want to support what I do you can support me on Patreon or paypal. Thanks!

Friday, 9 March 2018

Low Cost Surface Firmness Tester

If you're a broke datahead like me you probably have always wanted to measure your putting green surface firmness but haven't been able to justify the $1000+ expense to buy one of the fancy testers available on the market. The problem I have had is that I just wasn't sure if it would be a metric that would make a difference in the way I managed my golf course.

It was easy for me to justify the expense of a moisture meter almost 10 years ago because I could see how it would improve my operation. I'm still on the fence about the firmness tester so I asked twitter how I could make one for myself and as usual, was pleasantly surprised.

This rather simple firmness tester was brought to my attention but it was still out of my price range at around $500.

Dr. D made a great little video outlining these various devices and how they work.

I decided to make an even cheaper version than what the PGA currently uses, again, because I am not sure if this is something that is valuable to me.

I bought 2 steel balls that are close in size to a golf ball which is 1.68" in diameter. My steel balls are 1.5" but you could also use 1.75" balls. You can get these on Amazon.

My version uses your HOC gauge to measure the depth of the impression on your green. Don't tell your mechanic.

Instead of a washer I used an old bedknife that is the same thickness as the little knob below the HOC gauge.

center the hole with paint over the indent

Find a bedknife that is a similar thickness to the tab on the bottom of your gauge.
In order to get consistent data you need to drop the balls from a constant height. I use a flag stick (assuming all of your flags are the same height). I drop the balls from the bottom of the flag because no one else on my crew can reach the top!

This version requires you push down on the gauge to test the depth. This obviously introduces some error so be as careful as possible to not push too hard.

I take a few measurements then log them in my firmness tester spreadsheet found here.

I've been asked a lot about how much the balls should weigh. I don't think it matters much as long as all your balls are the same mass and size. The only reason to have a standardized ball would be to compare to other courses which isn't what this is for.

In time I expect to build an understanding of what this data means. What is firm and what is soft and if it's something that I care about enough to measure or invest further in one of the fancy units.

For now I've pulled this data into my maintenance HUD to see how important this data really is.

If you like my blog and want to support what I do you can support me on Patreon or paypal. Thanks!

If you like my blog and want to support what I do you can support me on Patreon or paypal. Thanks!

Wednesday, 7 March 2018

Turfgrass Maintenance HUD

I've talked about how to efficiently collect and analyze data on a golf course using google forms and google sheets on this blog. These free cloud based tools make is super easy to collect data in the field and have in instantly sorted and analyzed for use with decision making.

The trouble with having multiple sheets for data collection is that you have to go to all these sheets to get the relevant data. My turfgrass maintenance HUD (heads up display) solves that problem by aggregating all my data into one place. Now I can see all the metrics that are important to my agronomic decision making process.

I threw everything I have at this preliminary HUD design. The idea is that I will cut out the stuff that I don't use but only time will tell what is useful in my day to day grass growing decision making process.

The foundation of this HUD is the =importrange() function in google sheets. This function allows you to pull data from another spreadsheet into the current spreadsheet. This is how I get all the information into one spot.

All of the weather data is pulled from my weather spreadsheet which automatically updates each day and calculates the growth potential, evapotranspiration rate, dollar spot potential and precipitation data.

The growth potential data will help me understand the growing conditions. Whether it's too cool for growth or too hot I will be able to make more informed decisions about how much I push the grass based off of this data.

I also pull this data into my fertilizer spreadsheet to help me determine my weekly fertilizer rates etc.
My stimp data is pulled from my stimp meter reader sheet.

The growth rate data will give me a great idea of how fast the grass is growing and what kinds of issues I can expect whether it's disease, green speed issues, mowing frequency or clipping management.

Some might think that all this data takes away the art of greenkeeping. I think it allows me to produce better art as my understanding of how my grass is growing is now compiled in one central location where I can use it to make the best decision based off of the facts.

If you like my blog and want to support what I do you can support me on Patreon or paypal. Thanks!

Friday, 2 March 2018

MLSN MATH Step by Step

I've done a lot of talks recently all over the world about the MLSN guidelines and a common issue I come across is people getting hung up on the math. One of the biggest advantages of MLSN is giving the power to determine how much fertilizer to apply back to the superintendent, but if you can't figure out the math you are no better off than when you started.

If it wasn't already obvious, I love math. I see the world as numbers and use them to help me better understand what I see. This is one of the reasons the MLSN instantly made sense to me back in 2012. The numbers just didn't add up for me with fertilizer recommendations coming from things like BCSR or SLAN. It was almost like these recommendations were being pulled out of thin air.... The fact that the math behind the MLSN is freely available and quite simple to do should say a lot about the benefits of this system.

Before I start I would suggest checking out PACE Turf's Climate Appraisal form and Micah's MLSN Cheat Sheet. These tools can do the work for you and explain how to do this math for yourself. For you stubborn SOB out there I will now go through the math step by step with an example from one of my soil tests.

Now you can do this without testing your soil and simply just apply any fertilizer in the ratio found in the plant. This will ensure that you supply all the nutrients that the plant can use but will invariably lead to some waste because with this method you are ignoring the nutrients in the soil. If we account for the nutrients in the soil we can use them and save from having to apply that nutrient as fertilizer until we use up the soil reserves.

Apply fertilizer in this ratio and forget about it
But this isn't why you are here, you want to fine tune your fertilizer applications and have recently tested you soils. You want to use up your soil reserves and save some money!
MLSN Guidelines

Here's a soil test that I did a few years back.

Let's use the G1 sample for this example.

As you can see I have 37ppm of K in my soil and the MLSN guideline is also 37 ppm. Great I have enough, right?


I have enough for today but as the plant grows it will use some of that K and my soil test will dip below the MLSN guidelines. In the short term this is ok because there is a built in safety factor in the guidelines but after a while I will be in trouble.

So how much K will I use?

This is super easy to determine because as we know, K use is directly related to N use. It's a ratio. We can expect to use half as much K as N for any given time. How you determine how much N you apply is up to you. I like to use PACE Turf's climate appraisal because it takes my specific climate into account and allows me to fine tune rates over the course of a season.

For this example let's say I use 10g of nitrogen per square meter per year. That means that the plant will use 5g of potassium because half of 10 is 5 as determined by the above ratios.

Easy peasy.

But the MLSN guidelines are in ppm and we have g/m^2. To convert our 5g K/m^2 into ppm we need to multiply it by 6.7 to determine ppm in the top 10cm of soil. This will give us 33.5 ppm. This is the amount of potassium in ppm that we will expect our plant to use over the course of the season or whatever the time frame was that I used to determine my nitrogen rates for.

I'll use Micah's a+b-c formula to determine how much fertilizer is required.

We just determined what a is. That is how much K the plant will use and that is 33.5ppm

b is the MLSN guidelines which is 37ppm.

c is our soil test which was 37ppm as well.

So 33.5 + 37 - 37 = 33.5ppm

This makes sense because my soil test was exactly what the MLSN guidelines is so I essentially have to supply all of the K that the plant will use to stay above the MLSN guideline.

Ok so now I have the amount of K to add in ppm but we don't apply fertilizer in ppm. We need to convert back to g/m^2. To do this we divide ppm by 6.7 to get g/m^2 in the top 10cm. For our example this gives us 5 g/m^2. Ok so we just apply that much over the course of the year and we are good.


That is the amount of K to apply but we apply fertilizer K in the form of K2O. To convert from K to K2O multiply it by 1.2. This gives us 6g K/m^2 per year to apply.

For phosphorus this conversion factor is 2.29.

For the other nutrients there is no conversion factor!

So I need to apply 6g K/m^2. Personally I like to use 0-0-50 for my potassium source because it's cheap. Remember, the plant doesn't know the cost. So I divide 6g by 50% (that's what the numbers on the bag signify) and get 12g of 0-0-50/m^2 fertilizer per year. I have 4000m^2 of greens so that will require 48,000g of 0-0-50 fertilizer or 48kg or 2 bags or about $60 worth of fertilizer.

If you are using pre-blended fertilizer you need to multiply the quantity in liters by the density or mass per liter.
The fertilizer costs on my greens is an insignificant part of my budget. We literally spend more on toilet paper.

For phosphorus I can expect to use 1.3g/m^2 per year. Multiply that by 6.7 to get ppm and we get;

8.71ppm used per year for a

The MLSN is 21 ppm for b

I have 64ppm in my soils for c

So we do the math.

8.71 + 21 - 64 = - 34.29

What does a negative number mean?

It means you have more than enough nutrient already contained in your soil for the time frame you used to determine nutrient use compared to nitrogen. In this case it is a year.

I essentially have 34ppm extra in the soil above and beyond what I will likely use. If we divide this excess by the annual use rate of 8.71 we can get the number of years worth of phosphorus we have in the soil. In this example we get 3.93 years worth of P.

On my greens this isn't a huge deal because we don't use much P and the greens are small. If this was K and on my fairways I could expect to find huge savings.

If this number wasn't a negative, I would divide it by 6.7 then multiply it by 2.29 to determine how much P to apply as fertilizer.

For Calcium

I expect to use 0.08 x 10 = 0.8g Ca

0.8*6.7 = 5.36 ppm Ca for a

The MLSN for Ca is 331ppm for b

My soil has 367ppm for c

So 5.36 + 331 - 367 =  -30.64 ppm

Another negative number! 30.67 divided by the annual Ca use rate of 5.36 gives me 5.7 years worth of Ca in my soils. I don't need to apply it as a fertilizer. There is no conversion factor for Ca but don't forget to divide it by 6.7 to get it in g/m^2.


10 (nitrogen use) x 0.05 (magnesium ratio to nitrogen) = 0.5 grams of magnesium multiplied by 6.7 is 3.35ppm for a

The MLSN for Mg is 47 ppm for b

And we have 59 ppm in the soil for c

The Math;

3.35 + 47 - 59 = -8.65

ANOTHER NEGATIVE! I have more then enough Mg in my soil to sustain by grass for at least 2.6 years (8.65/3.35 = 2.6). There is no conversion factor for Mg but don't forget to divide it by 6.7 to get it in g/m^2.


10 x 0.06 = 0.6 grams of sulfur x 6.7 = 4.02 ppm of sulfur for a

MLSN is 6 ppm for b

I have 19ppm in my soil for c

4.2 + 6 - 19 = -8.8

There is no conversion factor for S but don't forget to divide it by 6.7 to get it in g/m^2.

It looks like the only things my greens need are nitrogen and potassium. Great!

To make applying the custom amount of potassium determined with the MLSN guidelines I divide the amount needed by the amount of nitrogen I expect to apply for the year.

6 (amount of K to apply)/10 (amount of N I expect to apply.

This gives me a ratio of 66% potassium to nitrogen. I can use this number when making custom blends of soluble fertilizer to apply in my sprayer for next to no money, or I can use this to select pre-blended fertilizers that I will spend a lot of money on to apply to my greens. Easy.

The soil test used in this example was done in 2015 which was 3 years after I had adopted the MLSN guidelines on my course. Nutrients like K that are used in larger quantities will quickly end up close to the MLSN guidelines using this strategy. If you think about it that's the entire point of calculating fertilizer requirements in this manner. It is to use what the soil can provide and apply what the soil can't provide as fertilizer. After a while, you will end up with soil test figures that are close to the MLSN guidelines. How long it will take to get to this point will be determined by how much your grass grows, if you remove clippings or not, how much you have in your soil, and what ratio that nutrient is used each year.

Potassium went to the MLSN guidelines on my low CEC soils in 1 year. As you can see I still had a few years to go for the other nutrients to get them to the MLSN levels.

From there I can continue to test my soils to ensure that my math is good, make adjustments because this is just math, not reality, and apply all the nutrients as required by the plant use.

So how does this method compare to the one I first described where we apply the nutrients found in the ratios in the plant?

Well with that method I would slightly underapply potassium but the safety factor in the MLSN would keep me safe. Eventually I would need to supplement the K in my soil.

I would also over-apply all the other nutrients but even then, they are so cheap this would only cost me maybe $20 per year over what I currently do on my greens ($130 annual fertilizer cost for 0.4ha in 2017).

If you are struggling through the math I hope this helps you figure it out. Once you figure this out, you will see that the MLSN, and fertilizing grass is actually quite boring. But this will help you focus your efforts to make meaningful improvements elsewhere.

If you like my blog and want to support what I do you can support me on Patreon or paypal. Thanks!