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Deer Park, WI

As we slog our way thru the bowels of the off-season, it appears the bloodiest war fought here was Marv’s pot stir on GPC renaming. One could fairly argue that the off topic message board wages far more damaging battles. Let’s leave that cesspool out of this discussion. It’s mildly contentious, pumpkin-related posts like Marv’s that capture my interest. Thus, gonna try to one-up my pot-stirring compadre with debate on soil potassium management. Those who’ve read my guide on pumpkin soil fertility will see that I’ve historically recommended aiming for 8% potassium base saturation, along with suggestions on how much potassium sulfate is necessary to achieve that goal. It is time for an update to that req. I’m sitting at the Morton building in SD listening to my soil fertility mentor, Neal Kinsey, discuss principles of nutrient management. He says “potassium builds fruit” along with myriad other reasons why K is beneficial for plants. However, too much of a good thing can become a bad thing.

2/25/2021 9:13:47 AM

Deer Park, WI

The trick was to find out where. I’ve learned that above 7.5% base saturation, K can inhibit manganese uptake, as well as other micronutrients. After reviewing hundreds of pumpkin patch soil tests from all over the place, the single most common trend I’ve observed is low manganese. As such, suggesting 8% base saturation K is no longer compatible with optimal ideals for managing nutrients. I will be adjusting my target for K to 5-7% base saturation. For those who own the guide and would like an updated req for K addition, feel free to reach out.

Circling back around to the pot stirring premise I opened with, I’m looking for debate/dialog on where “ideal” nutrient levels are for giants. Just because Joe or Neil Kinsey says so isn’t good enough. Not for me and surly shouldn’t be for you. I like to question everything, my own beliefs included. So let’s see what type of trouble we can get into here.

2/25/2021 9:24:18 AM

On top of Brush Mountain, Pa.

Okay Joe. I have spent a lot of time looking into what level of potassium we should be aiming for. I have not looked at a lot of soil test results but I have reviewed the literature on targets for soil nutrients. Here are my thoughts. Albrecht set the potassium target at 4% exchange site saturation. Astera suggests that 5% potassium should be the target. Solomon feels the target for potassium should shift with the CEC, the soil’s ability to deliver potassium. Solomon feels that unlike the other elements, no single ratio can be used to determine the right amount of potassium. He believes the higher the CEC the less potassium is needed. His numbers may be low because Solomon is trying to produce fruit with higher protein content while we are geared toward fruit size. I decided to go along with Astera. I make certain I do not short potassium though. Being slightly over 5% is better than being under. 7% may be a bit high. I am geared more toward tomatoes but I don't think what is needed for giant pumpkins is that much different, if at all. So, I say 5% or slightly more, but not as high as 7. Joe knows a lot about the "ideal soil" but it looks like on potassium our thoughts differ.

2/25/2021 10:17:05 AM

Grittyville, WA

Advancing eco agriculture sap analysis guru (John Kempf) says that applying a good bioavailable manganese will regulate potassium in the plant regardless of the soil level.

2/25/2021 11:24:50 AM

Grittyville, WA

https://www.bing.com/videos/search?q=advancing+eco+agriculture+manganese&FORM=HDRSC3

Not sure that link will work, but try it :)

2/25/2021 11:27:35 AM

West Pa

Try this one on for size.
https://johnkempf.com/the-ineffectiveness-of-potassium-chloride-as-a-fertilizer/

2/25/2021 7:05:40 PM

West Pa

Kempf interview Dr. Mulvaney, first part Ca then K

2/25/2021 8:45:52 PM

West Pa

Kempf interview Dr. Mulvaney, first part Ca then K.
http://regenerativeagriculturepodcast.com/the-fallacy-of-mainstream-potassium-and-nitrogen-fertilization-with-richard-mulvaney

2/25/2021 8:49:33 PM

On top of Brush Mountain, Pa.

The writer of these articles, a well recognized soil expert, says essentially that we do not need any additional potassium added to our soils as there is already enough present. This is because a standard soil test fails to measure the total amount of potassium in the soil which ultimately becomes available to the plants. Also he states that the fertilizer companies make a lot of money selling this unneeded potassium, especially potassium sulfate which is the most expensive source of the potassium we purchase. What do you think Joe? Solomon in his book recommends potassium but states that high potassium levels increase the carbohydrate levels in fruit making it less nutritious but supports adding potassium when levels are below his target value. Everyone I am aware of supports maintaining levels of potassium at least above 4%. What do you believe Joe? You are supporting level between 5% and 7%. Are there any other growers out there with an opinion?

2/26/2021 9:01:59 AM

Deer Park, WI

I was privileged to have Dr. Mulvaney as my soils professor when he published this work in 2014. I agree with his premise that there are generations of potassium banked in the soil that could offset the need for synthetic K ferts. This is beyond refute. What remains misunderstood is how to “unlock” the mineral for plant use. Biological and or chemical additives? Genetically modify crops with the keys? That’s where science needs to go before we abandon K applications.

I agree with the use of k-sulfate over k-chloride. Recent publication out of Purdue showing reduction in soybean yield following KCL application with speculation that it’s the chloride suppressing microbiological activity leading to yield loss. Makes sense, we use high doses of chlorides to suppress bacterial growth in our water systems.

5% K is good. Are 6-7 better? Hard to say. May never know. Instead, I feel confident establishing guardrails where 5% is the low and 7% is the high. Marv our thoughts on this may be closer than you think. There’s more nuance to fine tuning the dials depending on where mag and cal base saturation values fall as well. Hard to look at any of these cations in isolation.

2/26/2021 1:25:57 PM

Grittyville, WA

Natural sources of potassium... kelp, wood ash, compost and manure, and langbeinite.

2/26/2021 1:40:34 PM

President - GPC

Add leaves to source of K.

2/26/2021 2:42:21 PM

West Pa

With K, the plant will tell us if it needs more or less.
Video explains.
https://www.advancingecoag.com/webinars
“Tools for Plant Diagnostics of Mineral Nutrition”

2/26/2021 6:18:42 PM

valtierra/spain

Joe.. MICROORGANISMS THAT MOBILIZE POTASSIUM. ... Bacteria of the genera Bacillus, Pseudomonas, and Clostridium and fungi such as Aspergillus, Penicillium and Mucor solubilize potassium by releasing organic or inorganic acids that react with the minerals that contain them. i know the Bacillus megaterium (strain CB1802). Over the years I have used nitrogen (azos) and OF phosphorus (pseudonomas putida). I am looking for potassium (Bacillus mucilaginosus)
here this article.

https://www.researchgate.net/publication/6649034_Growth_promoting_effect_of_a_transgenic_Bacillus_mucilaginosus_on_tobacco_planting

2/27/2021 7:56:52 AM

valtierra/spain

Frauteuria aurantia also helps the mobilization of potassium.

https://controlbio.es/es/linea-inagro/1075-rhizosum-k

2/27/2021 8:04:16 AM

Lloydminster/AB

I’m sitting at 8.8%. As my percentage has crept up so have my weights. In my opinion my soil can not release enough during peak fruit growth...

2/27/2021 7:48:57 PM

Mn

7% was what I was at before I added my turkey manure in the spring. May have changed a little after that but Joe did give the report a look and it did help grow a 2350. Appreciate the help, if there is one thing that I attribute success to it's simple good soil. You can put in a lot of work but if you don't have great soil it really makes growing difficult.

2/27/2021 11:26:31 PM

Deer Park, WI

Kind words, Travis. Appreciate the nod. Don, been thinking about doing another soil test survey. Would be cool to build an online, open source database that includes soil tests and season end results. Crude to tie weights to soil results without additional context of other variables, however the power of numbers could possibly tease out trends. Rmen, thanks for the biological contributions. No doubt that greater understanding of how, what, when microbes help the release and uptake of plant nutrients will be a very important aspect of making major advancements in the patch and in agriculture in general.

2/28/2021 8:33:26 AM

Muddy Waters

Good Stuff Joe Thanks

2/28/2021 5:39:43 PM

Paradise Mountain, New York

Application of leaves at 20 ton/acre would also add on average 656 pounds of calcium, 96 pounds of magnesium, 44 pounds of sulfur, 1.5 pounds of boron, 58 pounds of iron, 22 pounds of manganese, 50 pounds of chloride, 4 pounds of sodium, 0.3 pounds of copper, and 3 pounds of zinc. The actual amounts of nutrients applied can vary considerably as shown by the concen­tration ranges in Table 1.

2/28/2021 5:51:24 PM

Paradise Mountain, New York

https://www.spectrumanalytic.com/support/library/ff/Plant_Nutrients_in_Municipal_Leaves.htm

2/28/2021 5:51:36 PM

Deer Park, WI

thanks for sharing that, Brat. Helps illustrate that while leaves have a pretty decent balance of nutrients, their primary value in the patch is as a source of organic matter.

To put the 20 ton/acre in perspective, you'd need 920lbs of leaves across 1000sq feet to achieve a similar nutrient profile. let that sink in for a bit. 920lbs of leaves, 1000sq ft.

a 50 gallon garbage bag stuff full of dry leaves weighs what, 5, maybe 10lbs? As such, that's 183-91 bags per 1000sq ft. Imagine trying to till in that volume of leaf material. 10-15 bags of leaves across this area is challenging enough to incorporate. Now 10X that.

Not doggin on leaves in the pumpkin patch. i use them myself each year. simply stating that leaves as a source of plant nutrients, in a vacuum, is impractical.

I would much rather fine tune pumpkin fertility with a soil test and concentrated, isolated nutrients to achieve the "perfect soil"

3/1/2021 8:15:29 AM