# First Soil test results - verify my plan please



## ajssbp (Apr 22, 2020)

Hey gang,

Here's the results of my first soil test from about a week ago:



I just tested my front yard which is a loamey clay growing predominantly fine fescue with some KBG mixed in. Backyard is a project for another time.

P and K are low. The Waypoint results sheet says 2lb/k of P and 3lb/k of K. Reading through Ridgerunner's soil test thread and looking at the MLSN #s, my K is on the lower end of acceptable. When I do the math from Ridgerunner's thread using 93PPM of K and trying to supplement to 126 I get closer to 4lbs/1000 (3.8) unless I'm doing my math wrong. So somewhere in the 3-4lbs of K/1000 sound about right?

The micros seem ok. I'm not really sure what to do with those, ie if it's worth supplementing. Is it worth pursuing a fert with iron in it for next season? I had planned on trying to find something with iron in it and some organic matter, but I'm not sure I need that anymore. With my high levels I'm not sure if there is a possibility of adverse effects from too much iron. Any other insights would be great. Thanks.


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## ken-n-nancy (Jul 25, 2017)

ajssbp said:


> ...
> P and K are low. The Waypoint results sheet says 2lb/k of P and 3lb/k of K. Reading through Ridgerunner's soil test thread and looking at the MLSN #s, my K is on the lower end of acceptable. When I do the math from Ridgerunner's thread using 93PPM of K and trying to supplement to 126 I get closer to 4lbs/1000 (3.8) unless I'm doing my math wrong. So somewhere in the 3-4lbs of K/1000 sound about right?


You probably already know this, but just in case, I'll mention it...

When the soil test results come back indicating that you should apply 2lb/ksqft of P and 3lb/ksqft of K, that isn't all at once, but spread out over multiple applications over time, presuming that you are applying at the surface to an existing lawn.

The general rule of thumb is to make applications of no more than 1 pound of each macronutrient (N, P, and K) per month when applying to the surface of an existing lawn. This standard recommendation has some margin in it for "safety" to not cause real bad problems with unintentional overlap from the spreader, but it's a good guideline.

So, you probably want to split those applications up into monthly applications for at least 3 months.

Also, just one note for whenever I see somebody in a snow-covered state like New Hampshire talking about potassium applications in the fall. Various studies have regularly shown that significant potassium applications, particularly in the fall, can significantly increase snow mold in locations that see extended snow cover in the winter.

Here are links to a few:

https://www.paceturf.org/gallery/detail/snow-mold-and-potassium
https://www.blog.asianturfgrass.com/2013/03/10-years-ago-today-a-startling-observation-about-potassium-and-snow-mold.html
http://www.hort.cornell.edu/turf/cutt/2008v4.pdf

Google can point you to many more articles on the topic.

Personally, I don't make significant potassium applications on our lawn after Labor Day, since we regularly see 60+ days of continuous snow cover in the winter, making us a great snow mold target. I don't know the microclimate in Grand Rapids, MI, but if you are likely to see more than 40 days of continuous snow cover in the winter, I'd wait until spring for the potassium applications.

Our sandy soil leaches potassium continually, so we are nearly always potassium deficient, so I make monthly applications of 1#K/ksqft from May through August, but none after Labor Day. Your soil has a much better CEC than ours, so your soil may retain potassium better than ours.


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## Ridgerunner (May 16, 2017)

Your calculations are close. Close enough, anyway. I get closser to 3.6 lbs of SOP. 126-93 = 33, 33 X2 = 66 lbs of elemental K/acre. 66/43.5 = 1.52lbs of elemental K/M. Convert elemental to K2O: 1.52 X 1.2 = 1.82 lbs of K2O/M. Calculate amount to SOP for 1.82 lbs of K2O/M: 1.82 X 2 = 3.64 lbs SOP/M.

When calculating K and P, I recommend using the shortcuts: 1 lb of K2O/M will raise soil test K levels by 18 pm and 1 Lb of P2O5/M will raise soil test P levels by 9 ppm. 126-93 = 33. 33/18 = 1.83. 1.83X2 = 3.66 lbs of SOP/M. Easier still, round off. 33 is close to 36 or 2lbs of K2O/M. Two pounds of K2O is 4 lbs/M of SOP. That way you can do it in your head. 

One other thing. As you have a higher CEC soil, I would target a higher level of K. Something in the 150-175 range. And as Ken (or Nancy) said, no rush on getting all of that down at once. Next year (or over the next 2 years) is fine, and don't forget to account for projected turf usage.


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## ajssbp (Apr 22, 2020)

Thanks for the info guys.

@ken-n-nancy, I didn't know about the correlation between K and snowmold, so thank you. We typically have snow cover from Dec through sometime in April, so we are certainly susceptible. That whole darn lake effect thing........

@Ridgerunner, thanks for verifying my math. I like those short cuts, I haven't seen those before, but it makes a lot of sense. My plan for this fall is basically to do nothing - I scalped/dethathed/overseeded my front yard a few weeks ago, so this fall will be babying that, with the real plan to start next spring.

As far as annual usage, I found this spreadsheet and punched in my local climate info and here's what it spit out: 

Edit: got this from Here with more info here

Reading that it's saying my turf will use 55 ppm of K per year. I know plants typically use 1/2 the K as N, so I suppose that works if I'm doing 3#N, but 55ppm works out to about 3 lbs of K2O using the 18ppm/lb cheat. I'm missing something. Any ideas? Thanks.


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## Ridgerunner (May 16, 2017)

1.67 lbs of elemental K/M is 72.7lbs of elemental K per acre (1.67 X 43.56). 72.7/2 = 36.4 ppm.
I'm a bit lost here too.


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## dwaugh (Aug 25, 2020)

@ajssbp I started playing around with that spreadsheet as well. In a MLSN thread I posted a link to a good video (I thought) that talks about the spreadsheet. I think that one assumption is that all clippings are being removed, and that some N will come from the organics in the soil. I would assume irrigation is also assumed. So if you are mulching, and not irrigating your grass will not use what the model predicts it will. In Ohio, my grass hardly grows. On a golf course the numbers will be more realistic. I need to watch the video again, because I think the model can be helpful in predicting the amount of nitrogen to apply each month based on the max growth potential of each month.

Here is a link to the video


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## ajssbp (Apr 22, 2020)

@dwaugh I'll have to watch that video later. Thanks.

So that is the best way to determine annual consumption of P and K then? Thanks.


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## Ridgerunner (May 16, 2017)

The PACE spreadsheet is a great method for determining fertilizer requirements. They've increased the MLSN levels, so it's no longer a case of walking on the edge which I disagreed with as it really made no sense on an upside vs downside basis.
Original MLSN values:
P: 21 ppm
Ca: 331 ppm
Mg: 47 ppm
K: 37 ppm
S: 7
Edited


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## dwaugh (Aug 25, 2020)

Ridgerunner said:


> The PACE spreadsheet is a great method for determining fertilizer requirements. (other than the error with P ppm and any other errors that might be included) They've increased the MLSN levels, so it's no longer a case of walking on the edge which I disagreed with as it really made no sense on an upside vs downside basis.
> Original MLSN values:
> P: 21 ppm
> Ca: 331 ppm
> ...


I think I now see what you are talking about with the PPM "error' I wonder if that has something to do with using a shallower depth of soil to make the conversion? The times 2 is based on 6 inches of soil, if they are assuming a shallower root system in a putting green (with very short grass), the conversion would change, I think.


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## ajssbp (Apr 22, 2020)

@Ridgerunner, so you would trust the PACE recommendations for the lb/1k sq ft but perhaps not the PPM?

I'm trying to wrap my head around the MLSN #s and the Mehlich 3 #s from the soil testing thread. Using K for example, the Mehlich #s are 75-175 and the MLSN # is 37. With my K of 93 I could burn the ~36 ppm used by applying 3 #/1k of N and still be above the MLSN. I get that. My question is in regards to the Mehlich range vs the MLSN. It seems like they are totally separate, and you shoot for one or the other, correct? Basically MLSN is the lower bound where it won't affect growth, but the Mehlich range is a more "optimal" range for growth? Trying to understand the interplay between the two. Thanks.


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## dwaugh (Aug 25, 2020)

Looking at the MLSN cheat sheet https://www.asianturfgrass.com/2018-02-03-new-mlsn-cheat-sheet/ is seems they are using a depth of 4 inches (.333 decimal foot, not 6 inches) for the ppm to 1000 square feet conversion.


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## ajssbp (Apr 22, 2020)

@dwaugh oh, that's interesting. I might have to rework the spreadsheet to reflect the 6 inch ppm #s. I might also put in an override so you can enter a manual goal and it'll figure out what you need for consumption plus supplementing to get to goal....


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## Ridgerunner (May 16, 2017)

> I wonder if that has something to do with using a shallower depth of soil to make the conversion? The times 2 is based on 6 inches of soil, if they are assuming a shallower root system in a putting green (with very short grass), the conversion would change, I think.





> Looking at the MLSN cheat sheet https://www.asianturfgrass.com/2018-02- ... eat-sheet/ is seems they are using a depth of 4 inches (.333 decimal foot, not 6 inches) for the ppm to 1000 square feet conversion.


That is a most excellent observation. I didn't consider that, and I should have.
That highlights an issue that arose when I first posted the soil test thread which I ended up discounting the 6" sampling depth given the wide range of target levels and the relatively high thresholds before nutrients become detrimentally excessive. In a nutshell, if you sample at 4", but the lab reports for the furrow slice depth, how do you apply the results from a soil test to make the PACE fertilizer calculations? Did PACE build in an adjustment factor? I loathe any return to the tortured calculations of the LL era. At least it would always be a 1.5 conversion factor @ajssbp
This is a problem for nimbler minds than mine @dwaugh


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## g-man (Jun 15, 2017)

My advise, don't get too wrap around the numbers. You are not deficient in K. You can improve your reserves. If you mulch your clippings, it will help your reserves.

Add P and K monthly when you can (weather/season depending) and retest in a year to see your levels. Don't expect a visual turf quality difference between a K if 90ppm and 150ppm.

Similar with P, while it is low per MSLN, Soldat studies don't show an improvement until it goes from like 3ppm to 10ppm.


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## Ridgerunner (May 16, 2017)

g-man said:


> My advise, don't get too wrap around the numbers. You are not deficient in K. You can improve your reserves. If you mulch your clippings, it will help your reserves.
> 
> Add P and K monthly when you can (weather/season depending) and retest in a year to see your levels. Don't expect a visual turf quality difference between a K if 90ppm and 150ppm.
> 
> Similar with P, while it is low per MSLN, Soldat studies don't show an improvement until it goes from like 3ppm to 10ppm.


@g-man Always bringing a healthy dose of perspective.


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