P and K consumption

[Brian]

I've been working on my soil fertility levels and finally have them about where I want them with P at 80-100#/ac. and K at 200-225#/ac. …. and now that I've got them there I would like to keep those levels!

I've seen a lot of information on the internet about P and K "removal rates," but they're all for ag crops that are harvested. Is there any kind of general rule of thumb as to what kind of P and K loss can I expect in a food plot? Or to ask the flip side of the same question, how much P and K will I need to add each year to maintain current levels?

 

[cutman]

If you aren’t harvesting a crop, the only nutrients that should be leaving your plot are from deer (or other wildlife) eating. It should be very easy to maintain P and K moving forward with minimal inputs. Only a soil test can show you how much to add each year, but I think you’ll be pleasantly surprised.

 

[X-farmerdan]

I would think you would need to know about your soils' abilities to hold those nutrients. Both P and K can and do leach thru the soil, but the rates are quite variable. Usually P holds on well while K's ability to endure is better than nitrogen, but much less than phosphorous. Soil test every other year for awhile. You'll soon start to understand.

 

[X-farmerdan]

I would think you would need to know about your soils' abilities to hold those nutrients. Both P and K can and do leach thru the soil, but the rates are quite variable. Usually P holds on well while K's ability to endure is better than nitrogen, but much less than phosphorous. Soil test every other year for awhile. You'll soon start to understand.

Mississippi? A ton of lime every third year? and 40 lbs of p and 100 lbs of k every other year?

 

[MarkDarvin]

I've been working on my soil fertility levels and finally have them about where I want them with P at 80-100#/ac. and K at 200-225#/ac. …. and now that I've got them there I would like to keep those levels!

I've seen a lot of information on the internet about P and K "removal rates," but they're all for ag crops that are harvested. Is there any kind of general rule of thumb as to what kind of P and K loss can I expect in a food plot? Or to ask the flip side of the same question, how much P and K will I need to add each year to maintain current levels?

What are you growing in your plot?

 

[Chipdasqrrl]

It may not be the answer you’re looking for, but as far as phosphorus goes, you’re better off unlocking the phosphorus that’s currently in the soil rather than adding more.
Most of the phosphorus in the soil isn’t in a form that plants can use. There is phosphorus fixing bacteria in the soil, just like there is nitrogen fixing bacteria for legumes. These bacteria turn the phosphorus into a form that the plant can use.
I’m not sure how easy it is to find since I haven’t tried it, but you could buy seed inoculated with phosphorus fixing bacteria or probably the inoculant itself.
As far as reducing the amount of phosphorus you lose, try to minimize tillage. It will massacre the phosphorus fixing bacteria and some of the phosphorus will leach out.
The same concept goes for Potassium, but phosphorus is more unavailable


Sent from my iPhone using Deer Hunter Forum

 

[Chipdasqrrl]

To add to that, an excess of inorganic phosphorus added to the soil by fertilizing will start to hurt the plants, especially in the long run.
Too much phosphorus in the soil will begin to tie up other nutrients that the plant needs, especially the micronutrients Iron and Zinc


Sent from my iPhone using Deer Hunter Forum

 

[Brian]

Thanks for all the information guys.

What are you growing in your plot?

Rye and wheat with annual clover and chicory.

 

[MarkDarvin]

Thanks for all the information guys.
Rye and wheat with annual clover and chicory.

Are you ripping it up or spraying it each year?

 

[Brian]

Mississippi? A ton of lime every third year? and 40 lbs of p and 100 lbs of k every other year?

I hope not!

When I purchased this property in 2014 it was a cutover pine plantation - In two plots i tested that first year ph was 4.9 and 5.1, P was 21 / 24 and K was 74 / 85. I limed at 2-4 tons an acre 5 years ago and ph was 6.2 and 6.6 when I test those plots a few months ago.

P and K have been a little more work, but I’m finally getting them up to my target levels of 80# P and 200# K- I guess I will do annual soils test for the next couple of years to see what happens

 

[Brian]

Are you ripping it up or spraying it each year?

I just let the plots go over the summer and until this year I’ve mowed in late Summer and disced a few weeks later. This year I tried throw-n-now for the first time - I was fortunate and got rain within 24 hours of putting seed out and plots are doing well.

 

[MarkDarvin]

I just let the plots go over the summer and until this year I’ve mowed in late Summer and disced a few weeks later. This year I tried throw-n-now for the first time - I was fortunate and got rain within 24 hours of putting seed out and plots are doing well.

If you're just scratching it up with a disc, I wouldn't get too worried about having to add P&K. You'll get a good amount of fertility from outside hauled onto your plot from elsewhere just as you'll have some hauled away. I'd even think you may have a gain. If you keep a rotation like that going, you shouldn't have to keep pumping more on.

You're sitting on 10,000 years worth of P&K in your soil. Keep the biology alive with diversity, season long green, and minimal tillage and you'll be set. Them little invisible soil workers will go to the cellar and free up enough to put out a crop each year and leave the rest in the bank. Maybe try to add a few extra things to up the diversity.

 

[X-farmerdan]

I hope not!

When I purchased this property in 2014 it was a cutover pine plantation - In two plots i tested that first year ph was 4.9 and 5.1, P was 21 / 24 and K was 74 / 85. I limed at 2-4 tons an acre 5 years ago and ph was 6.2 and 6.6 when I test those plots a few months ago.

P and K have been a little more work, but I’m finally getting them up to my target levels of 80# P and 200# K- I guess I will do annual soils test for the next couple of years to see what happens

Ashes to ashes and dust to dust. What starts as an acidic soil will, over time, revert to an acidic soil. I'd guess that's where you started although there are parts of Mississippi where the natural pH approaches neutral.

I've posted this map of native soil pH's before, but let's focus on your state.



Got not much to do with this, but the soil maps at the end of this link are interesting...

http://www.bonap.org/2008_Soil/SoilTypesRelatedMaps.html

 

[Brian]

Ashes to ashes and dust to dust. What starts as an acidic soil will, over time, revert to an acidic soil.

it’s that “over time” part I’m trying to figure out!

According to the map you posted, my native pH is something like 5.3 but after a couple of rotations of planted pines it was a little more acidic than that when I started at 4.9 and 5.1. I realize that it is constantly creeping back toward its natural state, I’m just hoping it does it a slow enough pace that I’m not having to apply a ton of lime every third year!

 

[MarkDarvin]

it’s that “over time” part I’m trying to figure out!

According to the map you posted, my native pH is something like 5.3 but after a couple of rotations of planted pines it was a little more acidic than that when I started at 4.9 and 5.1. I realize that it is constantly creeping back toward its natural state, I’m just hoping it does it a slow enough pace that I’m not having to apply a ton of lime every third year!

Wild guess here, I'm betting east of the rust belt is more acidic than nature intended due to the industrial age. The advent of scrubbers, ultra low sulfur diesel, and tier 4 engines put a damper on acid rain and soils are beginning to revert to more normal pH's in the east, and it's caused an environmental hazard to the eastern great lakes. Highly acid soil locked up soil phosphorus and prevented runoff. Now that soils are moderating, that P is coming unbound and ending up in Lake Erie and the Chesapeake Bay.