# How much P and K Per Application?



## VA Haymaker (Jul 1, 2014)

Sent off some soil samples on some fields I'm starting to reclaim and they are in bad shape.

I understand staging N - nitrogen, but what about P - phosphorus and K - Pot Ash? Stage it or apply the mother load all at once/now? Planting Teff in these fields next spring, Timothy the following fall. Don't anticipate plowing, but doing roundup and no till planting.

Any tips are much appreciated.

Thanks!
Bill


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## Trotwood2955 (Sep 4, 2012)

Im sure there could be an upper limit to what you would want to apply all at once simply because you would be putting on more nutrients than needed or cost effective. Otherwise you can put it all down, don't have to worry about losing it like you do N. I think you would be fine to put it down now or spring for a next fall establishment. The teff may use some of it but you can always add more and adjust later once the Timothy is established. P and K are more of a longer term investment.


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## rjmoses (Apr 4, 2010)

It depends:

Get your soil test results first, then figure out how much you need to bring K up to about 300 and P up to about 70.

Then figure out how much yield you expect in tons/acre. A rough number is about 50 lbs K per ton of yield and about 15 lbs P per ton. (These are rough numbers and can be affected by PH and soil type.)

Now here's the rub: Since you are talking no-till, you can't apply very much of either because they only move about 1/4" per year through the soil.

If I were you, I'd consider disking pretty deep and in several passes after spreading the P and K to incorporate it throughout the top 8" or so.

Let's us know the test results.

Hope this helps.

Ralph


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## endrow (Dec 15, 2011)

Planting a cereal rye cover crop now.Will do as much to move the P and K down as discing.


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## endrow (Dec 15, 2011)

Here in central Pennsylvania teff is just absolutely the most sensitive crop to establish. Don't know what it's like when your farming but if I was in the process of reclaiming some land teff would be way down the list as a choice of the first crop. If row crops are not an option it comes to mind. My Grandpa would have said in Pennsylvania dutch, you have to farm it in shape before you can sow those tiny seeds


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## endrow (Dec 15, 2011)

Typo I meant if you crops are not an option OATS comes to mind


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## VA Haymaker (Jul 1, 2014)

Here is one field's test results:

I am to apply the following:

N = 90
P = 110
K = 185
PH = 5.7
Lime = 1.25 tons per acre.

With other fields, I have divided similar test results in half for application, except lime, where I limit it to 1 ton per acre per application for no till.

All of my test results are somewhat similar - in magnitude.

Question is - this fall do I dump 110 lbs per acre of P and 185 lbs per acre of K on no till at once or divide up the application like I do lime and N? Will the P and K stay put and soak into the ground or wash away from rain? Land is pretty much flat on these fields, but a few rolling places too. Creek borders one field.

What are some typical N, P and K numbers you see off of your grass hay fields?

Thanks,
Bill


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## endrow (Dec 15, 2011)

Everybody's soil is different I would split apply it because we are well drained here. We always try to apply for the following crop. We never apply any less unless the soil test show and exccess. And we never and apply more or unless there is a massive deficiency. We spin it on and we do not have variable rate abilty . In some cases we have to come up with a happy medium. We do a lot of manure testing but again we have to use Book value many times, when we credit manure r and deduct the fertilizer applied. As we speak we are applying 20 units of nitrogen as AMS and 45 units of phosphorus and 100 units of potash. That is being spread into the live cover crop with a 5 ton tow spreader. In very early Spring we will credit whatever manure was applied, and spend on a blend which will have the remaining needed P and K for the crop and half the nitrogen. We will make a second pass with nitrogen when we do find a side or something like that. Of course skipping the end for the soybeans. We watch the soil tests very closely and by just doing it basically as a maintenance program everything stays in check. Same thing with lime, every acre we Farm gets 1 ton of lime every other year


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## rjmoses (Apr 4, 2010)

leeave96 said:


> Here is one field's test results:
> 
> I am to apply the following:
> 
> ...


I've been applying my P and K in late Feb/Early March, But I don't need build-up. I think I'd put the lime on now to allow the freeze/thaw cycle to suck it down. Also, based on your location, I'm guessing you're on more or less hilly ground so run off might be an issue for your fertilizer.

Ralph

Ralph


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## vhaby (Dec 30, 2009)

Normally we collect our soil samples from about the 6-inch depth. We estimate that the 6-inch soil depth represents about 2 million pounds of weight. The limestone recommendation is made for this depth. When we apply limestone to the soil surface and do not incorporate it deeper, this applied limestone is not very effective in changing pH in the plant rooting zone. This is true even with using very fine limestone. It takes several years for the neutralizing value of surface applied unincorporated limestone to move through this surface depth, especially in heavy clay soils, but also in the more sandy soils.

Ralph is right in recommending that the limestone be applied this fall. I'll take this a step farther and suggest that you disk-incorporate the fall-applied limestone right after application.

Ralph also suggests late winter application of the P and K and I again agree, but take his suggestion a step farther and recommend that you apply all the P and K and then disk incorporate it. The K will leach some over time, but the P is relatively immobile in soil. So when your 6-inch depth soil sample tested low in P and K, and you apply these on the soil surface with no incorporation by disking, your forage will quickly be sending its roots into soil that is deficient in P and K.


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## rjmoses (Apr 4, 2010)

vhaby said:


> Normally we collect our soil samples from about the 6-inch depth. We estimate that the 6-inch soil depth represents about 2 million pounds of weight. The limestone recommendation is made for this depth. When we apply limestone to the soil surface and do not incorporate it deeper, this applied limestone is not very effective in changing pH in the plant rooting zone. This is true even with using very fine limestone. It takes several years for the neutralizing value of surface applied unincorporated limestone to move through this surface depth, especially in heavy clay soils, but also in the more sandy soils.
> 
> Ralph is right in recommending that the limestone be applied this fall. I'll take this a step farther and suggest that you disk-incorporate the fall-applied limestone right after application.
> 
> Ralph also suggests late winter application of the P and K and I again agree, but take his suggestion a step farther and recommend that you apply all the P and K and then disk incorporate it. The K will leach some over time, but the P is relatively immobile in soil. So when your 6-inch depth soil sample tested low in P and K, and you apply these on the soil surface with no incorporation by disking, your forage will quickly be sending its roots into soil that is deficient in P and K.


Right on!!!

If you decide to disk this fall, spread it all (lime and fertilizer) now and work it down into the soil. Then consider planting a cover crop of some kind if you need erosion control. Maybe turnips?

Ralph


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## vhaby (Dec 30, 2009)

rjmoses said:


> Right on!!!
> 
> If you decide to disk this fall, spread it all (lime and fertilizer) now and work it down into the soil. Then consider planting a cover crop of some kind if you need erosion control. Maybe turnips?
> 
> Ralph


Now I have to disagree. When limestone (CaCO3) and P are applied and incorporated together, the P can precipitate (become tied up) as calcium phosphate. Better to apply the lime now and allow it to react with soil acidity so that most of the Ca attaches to the soil clay, and apply the P later. Have to agree that a cover crop of some sort likely is needed to prevent erosion this winter after incorporating the limestone. Some N, P, and K will be needed to grow the cover crop, but the majority of the recommended amounts of N, P, and K should be held back for late winter-early spring application.

Vincent


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## rjmoses (Apr 4, 2010)

vhaby said:


> Now I have to disagree. When limestone (CaCO3) and P are applied and incorporated together, the P can precipitate (become tied up) as calcium phosphate. Better to apply the lime now and allow it to react with soil acidity so that most of the Ca attaches to the soil clay, and apply the P later. Have to agree that a cover crop of some sort likely is needed to prevent erosion this winter after incorporating the limestone. Some N, P, and K will be needed to grow the cover crop, but the majority of the recommended amounts of N, P, and K should be held back for late winter-early spring application.
> 
> Vincent


Good point. And most P/K used by the cover crop will be returned to the soil.

Ralph


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## VA Haymaker (Jul 1, 2014)

Thanks everyone - great info!


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