Phosphorus to Potassium imbalance and fertilizer availability

[DRG3]

Hello, I'm looking for some input on how to handle and imbalance that showed up in my soil test. For each of my plots, whether they be clover seedings or oat/turnip combo's are coming back as "Very High" P content and "Low" K.
1) can the "Very High" P content stunt growth?
2) At planting last year we used 15-15-15, so it appears that K uptake is more drastic than P
3) I know the solution here could be a custom fertilizer, but in the past, i have been unable to find it for the smaller quantities I need.
4) Am I better off to put down no K and no P or continue to use fertilizer that has them both in equal amounts.

If it matters I went through the university of KY extension service as they offer free testing so I am pulling my terms straight from their form.

I'm sure I'm leaving out info that might be helpful, so please let me know what additional is needed.

 

[Hoytvectrix]

1) This would only happen if you had the Phosphorus tying up Ca or Al, which is fairly rare.
2) This is hard to know without knowing the crop grown and how much was "removed" by harvest or deer/whatever. More than likely you just had the field sit fallow at one point and you lost some K, or the field has for some reason built up P levels (could be from manure apps, for example).
3) You may just need a corrective application of a K fertilizer to get your soil test value up to "sufficient". You can try and build this overtime or do it in one shot, or not do anything at all if you don't want to.
4) That is up to you. Some on here do not use any supplemental fertilizer. I prefer to balance soil chemistry first and then scale back any fertilizer inputs. It all depends on how low is too low and whether or not it is limiting growth.

What were the test values for P and K? Also, include your CEC if you can. I would just upload your soil test report with your name and contact info omitted and I will take a look at it.

 

[DRG3]

What were the test values for P and K? Also, include your CEC if you can. I would just upload your soil test report with your name and contact info omitted and I will take a look at it.

Thank you very much. Here is a picture of the sample. That represents all my plot samples fairly well. I this case the plot last fall was oats and turnips. For a .3ac plot I put down 200lbs of 15-15-15. The prior year it was fallow and the year before that was the exact same crop and fertilize

 

[DRG3]

Did your crop look like it had problems?

No, it grew fairly well. I've had better, but it was far from a failure. The plants didn't discolor at the wrong time or anything like that. I thought the turnips could have grown larger leaves, but again, it worked out fine.

 

[SD51555]

No, it grew fairly well. I've had better, but it was far from a failure. The plants didn't discolor at the wrong time or anything like that. I thought the turnips could have grown larger leaves, but again, it worked out fine.

I wouldn't stress too much about the numbers then. You could send that exact sample to 5 different labs and get 5 different readings.

 

[DRG3]

I think one of my main questions is- using that sample to plan for this year- If all I can find is 15-15-15- will I do harm to new annual plantings from too much Phosporus, or if i elect not to buy fertilizer- and wanted to plat oats and turnips again, or eve oats and clover- will the plot suffer from Low K?

 

[Hoytvectrix]

I think one of my main questions is- using that sample to plan for this year- If all I can find is 15-15-15- will I do harm to new annual plantings from too much Phosporus, or if i elect not to buy fertilizer- and wanted to plat oats and turnips again, or eve oats and clover- will the plot suffer from Low K?

Based on that CEC, an ideal test value (depending on the extraction procedure used) should be somewhere between 200-300 ppm potassium. I wouldn't stress too much about that K level. Also, you aren't necessarily going to do much harm by applying some phosphorus. You can find cheaper sources of N and K besides a 15-15-15 though. I would check around. There are several fertilizer sources that provide N and K together that will be cheaper per pound of nutrient for N and K.

With all that said, I would just consider 50-100 lbs N/acre as urea or ammonium sulfate if you wanted to take more of a minimalists approach. For such a small area, and the fact that it is a food plot, I would recommend just keeping it simple.

 

[Wild Thing]

Soil test looks very good. I would go with the soil test recommendations - which is really what you paid for isn't it? I like to see both P and K at "Very High" levels, or at least "Optimum". The P is fine so I'm sure you can plant oats with no issues. But why let the K continue to lag? I would want the K level to be at least 200-300 ppm as Hoytvectrix suggested.

I can buy 0-0-60 almost anyplace around here. 2 bags of that is 60# of actual K. You wouldn't even need that much for 0.3 acres. Keeping it simple I would probably give that small plot 50# of 0-0-60 and 50# Urea (46-0-0) and call it good.

 

[bigboreblr]

I've looked at several state dept of AG recommendations for various crops. Oats soak up alot of potassium. There are farmers who mix pot ash and oat seed together while they plant it.

1/3 of an acre. You might be able to get away with a 12-0-12 fertilizer. I know walmart sells them. (2) 40lb bags of fertlizer would add 32lb/acre to your .3 acre plot. Decent ballpark without going over. They were selling them for $18 a bag in NY. I have a local AG coop that makes their own mixes. They sell pot ash (potassium) and urea by themselves.

IF you mixed their $27 a 50lb bag of 46-0-0 urea and 0-0-60 potash, a 40lb equavilent bag of 12-0-12 would be a little over $9. These high fertilizer prices I am seeing at AG coops were the equivalent to the pre-covid prices at the big stores.....

 

[4wanderingeyes]

12-0-12 has 12 pounds per 100 pounds.

 

[DRG3]

Really appreciate all of the help. I’d like to go ahead and try to find some mixes mentioned here without the P. I appreciate all the input.

 

[Wild Thing]

I've looked at several state dept of AG recommendations for various crops. Oats soak up alot of potassium. There are farmers who mix pot ash and oat seed together while they plant it.

1/3 of an acre. You might be able to get away with a 12-0-12 fertilizer. I know walmart sells them. (2) 40lb bags of fertlizer would add 32lb/acre to your .3 acre plot. Decent ballpark without going over. They were selling them for $18 a bag in NY. I have a local AG coop that makes their own mixes. They sell pot ash (potassium) and urea by themselves.

IF you mixed their $27 a 50lb bag of 46-0-0 urea and 0-0-60 potash, a 40lb equavilent bag of 12-0-12 would be a little over $9. These high fertilizer prices I am seeing at AG coops were the equivalent to the pre-covid prices at the big stores.....

I think you need to check your math bigboreblr. You won't get 32# of fertilizer from 2 (40#) bags of 12-0-12. Those bags only contain 12% each of N and K so each bag will only contain 4.8# of each - the rest is filler....... (40# X .12 = 4.8) 2 - 40# bags will get you 9.6# of each N and K.....(80# X .12 = 9.6)

One 50# bag of Urea (46-0-0) will contain 23# of N ....... (50# X .46 = 23)

One 50# bag of 0-0-60 will contain 30# of K........(50 X .60 = 30)

 

[FarmerDan]

Free advice! Worth every penny. I would do nothing. This alleged 'imbalance' is probably inconsequential for a third of an acre of anything. Your pH is good almost too good but I can maybe understand. Are you in KY? Since you used UK the UK lab (because it was free) I'd guess you did. Free is probably for the residents of KY? Where are you, which region? Map below. If you told me your soil test results without UK's interpretation I'd say - pH great; P -wow wow; K ok.

I might even question HOW you collected your soil sample? How many cores? Where they collected with a shovel or a good soil tube? How deep? In my mind soil test results are nearly worthless - singly. How the results change over time is important. But, a one-third acre food plot? It's fun to consider. Don't put too fine a point on it.

Bluegrass, right?

 

[bigboreblr]

I think you need to check your math bigboreblr. You won't get 32# of fertilizer from 2 (40#) bags of 12-0-12. Those bags only contain 12% each of N and K so each bag will only contain 4.8# of each - the rest is filler....... (40# X .12 = 4.8) 2 - 40# bags will get you 9.6# of each N and K.....(80# X .12 = 9.6)

One 50# bag of Urea (46-0-0) will contain 23# of N ....... (50# X .46 = 23)

One 50# bag of 0-0-60 will contain 30# of K........(50 X .60 = 30)

I corrected the values per acre basis divide by .3 = 32 lbs / acre on .3 acres. That one bag of urea is 76.6 lbs / acre omn .3 acres. That bag of pot ash is 100 lbs / acre or potassium on .3 acres.

I drive an hour out of my way to go to a local AG co-op. Another Ag co-op is on my way to my northern adirondacks hunting camp, but I have to take a 1/2 day from work because they close early.

Some guy have limited funds, time, and availability of stuff locally. But, the big stores have some decent stuff.

The wildlife eats most of the seedhead and some of leaves of the oats. However, you still have nutrients in that remaining oat thatch and dead roots. So, some potassium will comes back into the soil over a year or two.

 

[DRG3]

Free advice! Worth every penny. I would do nothing. This alleged 'imbalance' is probably inconsequential for a third of an acre of anything. Your pH is good almost too good but I can maybe understand. Are you in KY? Since you used UK the UK lab (because it was free) I'd guess you did. Free is probably for the residents of KY? Where are you, which region? Map below. If you told me your soil test results without UK's interpretation I'd say - pH great; P -wow wow; K ok.

I might even question HOW you collected your soil sample? How many cores? Where they collected with a shovel or a good soil tube? How deep? In my mind soil test results are nearly worthless - singly. How the results change over time is important. But, a one-third acre food plot? It's fun to consider. Don't put too fine a point on it.

Bluegrass, right?
View attachment 42408

Thank you. I’m actually in what’s showing as the fluorspar region on your map.

I did use a shove to collect my samples but the method was to clear the organic matter. Make a cut with the shovel so I could get a good vertical sample and then cut approx 4” slice since I couldn’t get a clean plug.

Thanks again for the help

 

[Bassattackr]

DRG3 - If you go to your local co-op you should be able to find Red Potash (0-0-60). For that small of acerage, one bag would more than suffice.. Most crops, including oats are high K users.

That's 60 / 2 = 30#s per bag x 1/3 acre = 90# per acre rate.

 

[FarmerDan]

This one continues to bother me. It's not the question or the answers, but UK's thought that a K level of 160 ppm is low. So I read this.
https://www.kygrains.info/blog/2020/10/19/your-uk-soil-test-report-use-and-interpretation

Its a good, simple but powerful explanation about how the author reads and values the test results. When i looked at DRG3's test results I read the P & K levels to be parts-per-million. But I think they are lbs/acre. It puts a little different spin on things. The point being interpretation and application of soil test results is a challenge.

 

[Wild Thing]

This one continues to bother me. It's not the question or the answers, but UK's thought that a K level of 160 ppm is low. So I read this.
https://www.kygrains.info/blog/2020/10/19/your-uk-soil-test-report-use-and-interpretation

Its a good, simple but powerful explanation about how the author reads and values the test results. When i looked at DRG3's test results I read the P & K levels to be parts-per-million. But I think they are lbs/acre. It puts a little different spin on things. The point being interpretation and application of soil test results is a challenge.

Agree that you have to know the difference between PPM and #/acre when reading the soil sample results. I have been using Waypoint Analytical Lab in Memphis for quite a few years now. BTW - Waypoint Analytical is the lab that actually does the soil tests for both Mossey Oak Biologic and Whitetail Institute so I just go direct to WA and cut out the middle man on the cost. Anyway, they clearly note on the Results column that the result is in PPM. If these results are in #/acre, the result would be double the PPM (i.e. in the K result below, the result would be 416 #/acre, which I agree is Very High). The result for K in DRG3's report shows K at 166 #/acre (or 83 PPM)...and I agree that that result is low and definitely needs some help.

 

[bigboreblr]

Another thing is what you see. Leaf discoloration. Id'ing what weeds are doing well in there. Noticing what you see in the general area for weeds and what you dont see at that spot.
I plant at a very non-uniform place. One low spot filled with organic matter over the years n years grows great. 20ft away is dead sand. Places with small rolling hills, glacial activity, or dormant creek / old oxbows can have really varied grow on a parcel.

You could be a good spot of soil, but there is shallow shale rock bed underneath, so it drys out. One place I planted looked great on paper...... But was an abandoned road, so the soil was very compacted.

Another thing which is somewhat addressed in these soil samples, is the soil capability to hold so much nutrients. Delicate sandy soils cant hold alot of charged ions like clay can. On a small scale I actually address this issue with fruit tree plantings on my lease. I bring some heavy clay soil and mix it into my sandy old acient seabed foothill forest. This way I can give it a decent bit of fertilizer and can apply lime without overdoing, or having is just wash away either.

 

[SD51555]

There's a really good talk from Dale at Green Cover on potassium. I'd give it a watch, cause it'll change your view of how the nutrient cycle works. If I had a soil test that showed zero potassium, I still wouldn't put any on.