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soil tests = no P or K is needed ???

americanlawn

LawnSite Fanatic
Location
midwest
If soil tests show that P & K are not deficient, are these nutrients still needed (especially potash)?

(Results from over 200 soil tests we did a few years ago revealed deficiencies only in nitrogen and several micro nutrients)

So if a bag of 44-0-0 slow release fert costs the same as 28-4-6, or 31-3- 5, or 34-0-5, why not go with the 44-0-0 XCU or PPSCU at a lower rate to increase profit?

Any thoughts? Negatives/positives? Timing? What are your thoughts/experiences? Just curious - been wondering for a long time. Thanks
 

rcreech

Sponsor
Location
OHIO
If soil tests show that P & K are not deficient, are these nutrients still needed (especially potash)?

(Results from over 200 soil tests we did a few years ago revealed deficiencies only in nitrogen and several micro nutrients)

So if a bag of 44-0-0 slow release fert costs the same as 28-4-6, or 31-3- 5, or 34-0-5, why not go with the 44-0-0 XCU or PPSCU at a lower rate to increase profit?

Any thoughts? Negatives/positives? Timing? What are your thoughts/experiences? Just curious - been wondering for a long time. Thanks
Larry,

Here is my take on the subject.

Typically Nitrogen isn't listed on a soil test and it is one of the most mobile nutrients and by the time you pull the sample and get the results it would have already changed...especailly if not packages and dried correctly.

Is that something you request? Any just wondering why you would.

If you have a soil test where P and K is adequate...I feel there is no reason to add more.

P and K are both imobile in the soil (at the levels you see in a lawn situation) as you don't have to worry about them moving unless you have soil loss or plant uptake and removal. In a lawn situation neither of these issues should become a reason.

Now if the customer removes clippings this would maybe make me think the other way because now you are dealing with nutrient removal.

I don't put any P on any of my lawns and I do run a little K with my 30-0-10, but at the end of the day I am putting very little K down.

Why buy the P and K and then add it where not needed. Nobody benefits from it and you pay for it out of your bottom line!
 
OP
americanlawn

americanlawn

LawnSite Fanatic
Location
midwest
Thanks buddy -- that's what I was kinda wondering. We've never used a 44-0-0, etc after April 1st or before late October, but I've always wondered why. I spose cuz my sales reps recommended what others were using??

Several years ago, we used alot of "synthetic-organic" liquid fertilizers. Main reasons: low salt content, no chlorene, and they offered several micro's we could not buy in a bag. We thought this was the way to go.

http://www.agroliquid.com At that time, they were mostly agriculture oriented, but they began to offer turf & ornamental formulations too. They were attempting to expand into our market with their turf & ornamental formulations, so they offered us free soil samples. They took soil samples from approx 214 of our accounts throughout central Iowa. Then they sent them to an independent lab for final results. All this was free to us.

Just under half of the samples were taken from "loam" soils, and the rest consisted of "clay" soils. Loams soils didn't lack much (just a little nitrogen for the most part), but nearly every "clay" soil indicated a huge lack of nitrogen -- along with deficiencies of several micro's (mainly iron, manganese, zinc, copper, and boron).

We never requested to include/exclude nitrogen as part of their soil tests, but they did. Regarding mobility in the soil, I was told that iron was even more mobile in the soil than nitrogen. Go figure.
 

phasthound

LawnSite Fanatic
Location
Mt. Laurel, NJ
Good info guys. How much of the P & K in the soil is plant available? I think it's also important to be adding some organic matter along with NPK. By providing food sources for soil microbes you can enhance nutrient uptake. It is the microbes that mineralize nutrients into plant available form.
 
OP
americanlawn

americanlawn

LawnSite Fanatic
Location
midwest
Thanks Barry. I has hoping you would chime in. Not sure about how much available P & K cuz we didn't personally take soil samples. Figured those guys knew what they were doing. They're mainly into Midwest farming (I think).

But I'm with you regarding organic matter. So is my brother (who runs our IOWA family farms). Sh$t ---- I'll even listen to Rodney (even though he's from Ohio:hammerhead:) :laugh::laugh: (Sorry rcreech) :laugh:

Seriously, my brother has run his share of "honey wagons". Also prefers "no till", etc whenever possible. IMO turf/ornamental care benefit from the same values. Weird but true, cuz most plants/soils have similar needs.

I'll shut up now and hope for other feedback. Thanks.

Good info guys. How much of the P & K in the soil is plant available? I think it's also important to be adding some organic matter along with NPK. By providing food sources for soil microbes you can enhance nutrient uptake. It is the microbes that mineralize nutrients into plant available form.
 

grassman177

LawnSite Fanatic
i have been thinking the same thing larry. i can not lose turf vigor and save money and not add unneeded minerals to the soil , all in one bang.

it is still needed during seeding and fall time to have extra that is soluable as much is locked up and large amounts are not available at once for the extra root boosting.
 

DA Quality Lawn & YS

LawnSite Fanatic
Location
Rochester, MN
Good thread Larry. I have run a few soil tests on our clay tight-as-heck soils around here in so. MN and found P and K to be ok and was also told they are tightly held in the soil structure. So, then why not just run xx-0-0 ferts with some select micros?
 

Smallaxe

LawnSite Fanatic
i have been thinking the same thing larry. i can not lose turf vigor and save money and not add unneeded minerals to the soil , all in one bang.

it is still needed during seeding and fall time to have extra that is soluable as much is locked up and large amounts are not available at once for the extra root boosting.
The bad thing about adding P at seeding time, is that, P inhibits the activity the activity of AM Fungi. AM Fungi is better for the vitality of your new grass, in the long run... :)

Therefore, I believe. that additional P is not needed for seeding; especially if there is plenty there at this time. In fact, there may be too much, P already, for healthy AMF to grow in the plant.
 

Jason Rose

LawnSite Fanatic
Ok, here's my question, other than actual science, we were always told to use a "balanced" fertilizer 3:1:2 ratio usually. Then prices of materials start going sky high and in order to keep prices down for the customers (us from the fertilizer suppliers) they started ommiting the P out of the mix. Then K began to rise in price dramatically and now they are omitting it as well. At first everyone was mad because it was going to be bad for the lawns to be only applying N all the time... Then some started looking at the real science of it, and now we question why we were using the "balanced" fertilizers in the first place!

I too have had a few soil tests done, and same results here. P and K are generally "high to very high" in the soil. BUT... We know they are also generally "locked up" in the soil. Does this mean they aren't really available for plant uptake? If that's the case, then when we add some via fertilizer, is that being taken up by the plants or is it just going into the soil profile and adding to what's there already? If the plants aren't able to use what's in the soil because it's locked up, and they can use, and need, what we are adding with fertilizer, dosn't it make sence to continue adding it? Instead of soil samples shouldn't we be doing tissue sample testing to determine what the plants NEED, not what's in the soil. Or a combination of both and see what's there and what's needed, and if what the plants need is already there, finding a way to 'unlock' them in the soil.
 

Kiril

LawnSite Fanatic
Location
District 9 CA
Typically Nitrogen isn't listed on a soil test and it is one of the most mobile nutrients and by the time you pull the sample and get the results it would have already changed...especailly if not packages and dried correctly.
This is true for nitrates with respect to leaching, ammonium is less prone to leaching. Sample handling is really only a factor with regard to contamination, however if you want to get an N breakdown (i.e. nitrates and exchangeable ammonium), then you should air dry the sample. That said, I believe total N is the better test to get for management decisions in the landscape, so proper drying becomes a less important issue.

I do agree that field determination of N availability (nitrates in particular) will provide a better picture of your soils current N status, but not really necessary for your typical landscape IMO.

If you have a soil test where P and K is adequate...I feel there is no reason to add more.
Agreed

P and K are both imobile in the soil (at the levels you see in a lawn situation) as you don't have to worry about them moving unless you have soil loss or plant uptake and removal. In a lawn situation neither of these issues should become a reason.
Any ion in solution can be leached. Positively charged ions (cations) are less prone to leaching losses, but that does not mean it cannot occur.

Good info guys. How much of the P & K in the soil is plant available? I think it's also important to be adding some organic matter along with NPK. By providing food sources for soil microbes you can enhance nutrient uptake. It is the microbes that mineralize nutrients into plant available form.
Microbes mineralized some nutrients, not all nutrients.

I too have had a few soil tests done, and same results here. P and K are generally "high to very high" in the soil. BUT... We know they are also generally "locked up" in the soil. Does this mean they aren't really available for plant uptake?
Out of the two, P is more likely to be found in non-labile pools (i.e. not plant available) than K. Organic matter will help keep P in the active and labile pools.

If that's the case, then when we add some via fertilizer, is that being taken up by the plants or is it just going into the soil profile and adding to what's there already? If the plants aren't able to use what's in the soil because it's locked up, and they can use, and need, what we are adding with fertilizer, dosn't it make sence to continue adding it?
This would be the reason why many times you will find high P in soils that are continuously fertilized with a "balanced" program.

Instead of soil samples shouldn't we be doing tissue sample testing to determine what the plants NEED, not what's in the soil. Or a combination of both and see what's there and what's needed, and if what the plants need is already there, finding a way to 'unlock' them in the soil.
As noted above, increasing your SOM will help keep P available for plant use. Encouraging mycorrhizal associations with your plants will also help.

The way I look at it ... soil sample to guide soil management decisions, tissue sample to determine/fine tune observed problems with your plants. If you observe a problem with your plant(s), you really need both tests to determine the best course of action. A tissue test alone won't give you enough information to effectively manage your soil, and a soil test alone may not give you enough information to manage a plant deficiency. Reason being .... some observed problems may not even be related to nutrients at all, but rather other management/environmental factors the affect plant nutrient uptake/availability and/or plant health.
 
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