Soil test confusion help

[RGrizzzz]

Last spring, we applied lime to most of our food plots based on previous soil test results. We retested two weeks ago to see how things look now. They're looking a lot better, but there was one confusing piece of information. Two plots a few hundred yards apart both tested at a pH of 6.3. One plot called for more lime while the other didn't. I reached back out to Penn State for clarification, but was curious if anyone here has any thoughts. Both tests listed "wildlife food plot" as the crop, so the recommendations should be the same. Why does one plot call for more lime, while the other doesn't?

 

[Mennoniteman]

Because

Last spring, we applied lime to most of our food plots based on previous soil test results. We retested two weeks ago to see how things look now. They're looking a lot better, but there was one confusing piece of information. Two plots a few hundred yards apart both tested at a pH of 6.3. One plot called for more lime while the other didn't. I reached back out to Penn State for clarification, but was curious if anyone here has any thoughts. Both tests listed "wildlife food plot" as the crop, so the recommendations should be the same. Why does one plot call for more lime, while the other doesn't?

It's because you're so low on magnesium, and the best way to boost magnesium is to apply hi-mag lime. The 6.3 ph is acceptable for a wildlife food plot, but the low magnesium isn't. Make sure to use hi-mag lime, not calcium lime.

 

[MarkDarvin]

Looks like you put on a hot dose of calcitic lime and didn’t stir it in.

What tools did you use to pull your sample?


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[RGrizzzz]

Both plots were sampled using a soil probe.

Their mag numbers were slightly better in 2022 than 2020.

The dump plot that needs the mag isn't real big. Are there any other ways to boost mag easily?

 

[MarkDarvin]

Both plots were sampled using a soil probe.

Their mag numbers were slightly better in 2022 than 2020.

The dump plot that needs the mag isn't real big. Are there any other ways to boost mag easily?

Dolomitic lime. I’m not sure where you’re located, but tractor supply has Waukesha lime. That would do it. I believe Mayville is also dolomitic. Thrifty white is not.

I don’t know that I’d get too excited about correcting it just yet unless it’s not a big deal to do so. I might carve off a sample area and put down a half ton rate to see if it grows any better than the untreated area, just for my own curiosity.


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[RGrizzzz]

Dolomitic lime. I’m not sure where you’re located, but tractor supply has Waukesha lime. That would do it. I believe Mayville is also dolomitic. Thrifty white is not.

I don’t know that I’d get too excited about correcting it just yet unless it’s not a big deal to do so. I might carve off a sample area and put down a half ton rate to see if it grows any better than the untreated area, just for my own curiosity.


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There's a supply yard near by that will load a scoop, about a ton, into our small trailer. That will cover what we need, when we have time. They usually have high mag lime.

 

[Mennoniteman]

Epson salt is magnesium, if you can find it cheap. But you could use some lime anyway...

 

[RGrizzzz]

Epson salt is magnesium, if you can find it cheap. But you could use some lime anyway...

I likely have a few random bags around the house. What kind of rate would I need to apply it at?

 

[Mennoniteman]

I likely have a few random bags around the house. What kind of rate would I need to apply it at?

I'd say not less than 2 lb and not more than 12 lb per acre. Magnesium is also often applied as a foliar spray by farmers in low magnesium soils as its readily taken in by plant leaves, and there's also a fertilizer product called K-Mag that's sulfur, potash, 11% magnesium that farmers use, but both of these are things to do if magnesium is low, and PH is high, which is a common problem. I'd consider buying several bags of K-Mag if available.
Since your PH is also low, so, while Epson salt helps short-term, your cheapest, easiest, most effective long-term solution is to apply hi-mag lime sometime.

 

[Mennoniteman]

I just re-read your soil tests, on the top one that's good on magnesium you are low on sulfur at 12 ppm, which should be addressed as well. 15 ppm is the minimum baseline, the lower test is 16, which is ok, but still considered in the lower range. Just to give you an idea of where your sulfur is at, 50 ppm is considered on the high side of acceptable. 2 lbs per acre of sulfur raises the ppm by 1, so 6 lb per acre would get the to top plot to a required minimum level of 15 ppm.

 

[RGrizzzz]

I just re-read your soil tests, on the top one that's good on magnesium you are low on sulfur at 12 ppm, which should be addressed as well. 15 ppm is the minimum baseline, the lower test is 16, which is ok, but still considered in the lower range. Just to give you an idea of where your sulfur is at, 50 ppm is considered on the high side of acceptable. 2 lbs per acre of sulfur raises the ppm by 1, so 6 lb per acre would get the to top plot to a required minimum level of 15 ppm.

I just picked up a bunch of gypsum cheap via FB marketplace. Is there a calculation for how much lbs of gypsum/acre will raise sulfur ppm? (Roughly. I realize there are lots of variables) Michigan state recommends 20-40lb/acre.

 

[Mennoniteman]

I just picked up a bunch of gypsum cheap via FB marketplace. Is there a calculation for how much lbs of gypsum/acre will raise sulfur ppm? (Roughly. I realize there are lots of variables) Michigan state recommends 20-40lb/acre.

I've never applied gypsum myself, but I know farmers talk about putting 1/2 to to 2 tons per acre. Gypsum is going to be a very good thing for your soil, and you don't need to worry about applying too much, I'd put on what I can afford, wait a year and soil test for sulfur again.

 

[RGrizzzz]

I only have enough to apply roughly 100 lb/acre, which should be enough to get the Sulfur up to minimum levels. Maybe next spring it'll get a heavy dose.