# Bulk application on alfalfa



## stack em up (Mar 7, 2013)

I've been watching too much Hefty Boys or something, saw their show a couple weeks ago and made me think. P and K are both extremely immobile in the soil, that we can agree on. Their recommendation is to apply your P and K needs for the length of how long you plan to have your stand, before you seed. I spread a little P and K after each cutting, and hope for a rain to take it in. Research shows it only moves about 1/2" a year, so basically nothing. Thoughts?


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## hillside hay (Feb 4, 2013)

We have quite a bit in our soil so I just replace it as I go.


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## danwi (Mar 6, 2015)

Wouldn't you have some fine roots close to the surface to take nutrients in? besides the ones that go deep


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## hog987 (Apr 5, 2011)

If your really short on a nutrient its not totally a bad idea. Most people who want to build the soil will add a bit more than removal. But if your really short of something it a good idea to put a bulk amount down so for the next few years your not shorting yield. But dont apply too much of something so it can become toxic to the soil. But the real answer is it depends. Worth looking into for sure.


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## rjmoses (Apr 4, 2010)

I've heard numbers from 1/8" to 1/2" P&K migration per year, but I'm Guessing this has a lot to do with soil type--slower in clay soils, faster in sandy soils.

When planting a new field, I often apply double the P and K annual rate, then disk it in 6 to 12" deep. My thinking is that this 1) allows it to get to work sooner and the plants will develop deeper roots, thus preventing winter kill , 2) prevents loss due to wash off, 3) allows the soil to reach equilibrium sooner.

I wonder if there are any studies on P&K migration rate and soil types as well as studies on the time it takes for P&K to activate?

Ralph


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## reede (May 17, 2010)

Alfalfa will consume K, so if you put a bunch down, it can use it up fairly quickly. It does like K.

K is much more mobile than P in the soil. Fall a year ago, we got 2/3 of a year's worth of rain in 3 months, from Oct1-Jan1. I was doing a monthly soil test on one field, and my K levels dropped by a bit over 1/3rd. So, with a lot of moisture, K will definitely move.

I agree with Ralph on if you are plowing before planting, that you'll probably mix nutrients in down deeper than the depth you go with soil testing. Good time to get pH adjustments in as well, rather than waiting for them to trickle down through the depth of the soil.


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## carcajou (Jan 28, 2011)

I applied 150lb actual of P along with extra K,S, and boron prior to seeding Alfalfa last year. Too early to tell the long term benefits. Our soils are lacking P as a rule. I hope to try a test field soon with enough P for 6 years, but it won't be on rented ground.


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## swmnhay (Jun 13, 2008)

That could be $500 a acre all up front.I'll apply it annualy.Plus there would me quite a bit of N in the P that I'd sooner have spread out more even-annually


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## r82230 (Mar 1, 2016)

My understanding how fast stuff moves through soil has to do with CEC numbers. The problem is I don't remember the relationship of CEC with movement of water/nutrients . Hopefully, someone better informed (or better memory) will chime in.

Being I am 100% no-till I just spread everything on top, relying on moisture migration to carry to the root structure. But I do start a year or so in advance of seeding to alfalfa soil sampling/building the nutrient levels, then just randomly sample going forward (once I have got everything up to the levels I desire).

Larry


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## stack em up (Mar 7, 2013)

Just had a lengthy discussion with my agronomist about this. He is of the opinion that I'm better off doing it the way I usually spread, 4 times per year. His thought process is applying a massive amount up front will help the first year, maybe 2, but will overuse P and K, possibly leading to dangerous levels in tissue samples and hat samples. He's never had anyone try it so he's not sure of that though.

I guess it's what I figured, but if we don't stop to question why we do things a certain way, we would never try anything new.


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## qcfarms (Dec 14, 2014)

I found an interesting read from the Noble Foundation.

https://www.noble.org/news/publications/ag-news-and-views/2016/december/best-times-to-apply-phosphorus-potassium/


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## vhaby (Dec 30, 2009)

Good read from Dr. Funderburg at Noble Foundation, except that calcium, iron, aluminum, etc. are not particles but chemical elements.

If a soil is tested as very low in phosphorus, I suggest that all the fertilizer phosphorus be applied early in the season in order to not have P be deficient for plant uptake. If soil is in the high medium to high levels for soil test P, I suggest that, if a producer wants to do so or if it's more economical to do so, the recommended amount of P fertilizer can be applied a little at a time throughout the season to replace plant removal. In reality, only about 25% of applied fertilizer phosphate becomes available for plant uptake in the year of application.


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