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Deer Park, WI

As a student of the U of I, Urbana-Champaign, I have had the privilege of studying under Dr. Saeed Khan and Richard Mulvaney. Experts on soil fertility, these out-of-the-box thinkers have long been researching and publishing on the concerns of conventional agricultural practices, notably the excessive use of N-P-K fertilizers.

Khan and Mulvaney have just released a landmark scientific publication that will most certainly stir the pot relating to potassium testing and fertilization.

For science geeks, the study can be found here: http://journals.cambridge.org/download.php?file=%2FRAF%2FS1742170513000318a.pdf&code=59e9a299458dd2068a9e7b504bdd5319

If you have trouble copying and pasting that link, simply type "potassium paradox" into your search engine.

Continued...

11/8/2013 9:54:31 AM

Deer Park, WI

For those who appreciate the crib notes version, here you go-

The authors present an exhaustive analysis on the variability of soil potassium testing and resultingly conclude that soil potassium testing, due to its extreme variability, has no practical use for guiding potassium fertilization. WOW.

The authors also present overwhelming data that suggest fertilization with muriate of potash (KCl), the most common and cheap potassium fertilizer used in ag today, has no basis for increasing yield in grain cropping systems. WOW.

As if that wasn't enough, they go on to provide evidence that KCl fertilization actually can limit yield as well as negatively impact the food supply. The high doses of chloride ions (the second half of the KCl equation) disrupt uptake of other nutrients and can cause the nutritional profile of crops to take a turn for the worse. WOW.

11/8/2013 10:01:17 AM

Deer Park, WI

What does this mean for giant pumpkin growers? Hard to say. Its common knowledge for competitive growers to consider "potassium pushes" after fruit set and into the homestretch to help squeeze out the last few pounds.

What basis exists for this principle, however?

The authors of the paper provide considerable evidence that soil contains massive reserves of potassium, without fertilizer inputs. In fact, continual soil tests on a university research plot that has never received potassium fertilization, only return of crop residues, has shown a increase in soil K test levels over the course of a 4 year study period.

11/8/2013 10:09:47 AM

Deer Park, WI

Here are the takeaways for me. By no means do I claim expertise on this matter, Im just a guy who wants to grow a WR but not break my bank or wreck my soil trying.

Soil testing still has a purpose. While the study suggests that soil K testing cannot reliably be used to guide potassium fertilization for increased yield, it can still be used to determine if your soil is extremely deficient or extremely high. In which case, decisions can be made regarding better management.

The authors convince me that the soil is an incredible storehouse of potassium and if a soil test shows "optimal" or higher K levels, no fertilization will be necessary. Potassium is relatively immobile in the soil, meaning it doesnt leach out the way nitrogen does. and if we arent pulling off tons of crop per year (a one-ton pumpkin is 95% water, only a fraction is potassium), we are not depleting soil potassium reserves.

Lastly, when/if potassium fertilization is warranted, using potassium sulfate (KSO4) is a preferable form. Plants and soils welcome sulfate. They dont like Cl in the KCl form.

Hope this review helps...one step forward in making us smarter and more efficient in our gardens.

11/8/2013 10:19:21 AM

BC, Canada

Joze, Thanks for posting this. I knew from other postings you have done that you were some kind of science geek, LOL.
I really enjoy reading studies like this to help me become a little more conversant in the area of soil fertility and fertilization. One thing about science, the more we learn, the more questions we have.

11/8/2013 11:50:13 AM

Seattle, WA

Thank you for sharing, I found this really interesting! Are you aware of the Yahoo Group "soilandhealth"?

It's moderated by Steve Solomon and is a good forum if you're interested in this sort of thing. I shared the link over there and am curious to get feedback as well.

We naturally have high K soils here in our area of WA, and I wasn't aware of how high K can increase the mobilization of cadmium and it's detrimental effects on livestock and human health.

~Tad

11/8/2013 12:27:43 PM

Little-TON - Colorado

Oh....the stock in KDL is dropping...Pete

11/8/2013 3:10:08 PM

Massillon, Ohio

I love the way you have of making this complicated "stuff" understandable. Thanks Joze....you're the best!

11/8/2013 7:59:53 PM

Sourthern Utah

jose,, i must say thanks,, that was a great short read,, appreciate you and all the efforts you put into these little short layman notes that are shared with the bp community, curt

11/8/2013 8:39:10 PM

Colorado

KDL isnt chloride... its the chloride that is the problem...

11/8/2013 9:09:59 PM

Deer Park, WI

I appreciate all the kind words, folks. And am always happy to digest the science and make it palatable for the growing community.

11/8/2013 11:01:32 PM

Joliet, IL

Great stuff Joe. It made me look at the labels of some fertilizer products I use. This lead me to a nice site that explains different forms of fertilizers in language easy to understand.

http://www.ctahr.hawaii.edu/mauisoil/c_material.aspx

What are your thoughts Joe about foliar feeding potassium? I use Recover RX 3-18-18 starting about 25 days after fruit set until the end of the year. I haven't used the 0-0-25 finisher I use to foliar after day 50 for fear of inducing an early rate of maturity. 2 of my 3 pumpkins grew past 100 days this year but i am not sure if just the cooler weather this year or from not using the K finisher I used to use. I spray the 3-18-18 once per week after day 25 with stihl fogger.

Does it still make sense to foliar potassium like in a balanced form 3-18-18 just to ensure there is plenty in the plant at critical times of pumpkin growth and to maybe just avoid using it as a K as drench or soil additive? And sounds like if potash is added to soil it should be in sulfate form instead of Cl form.

11/9/2013 8:36:32 AM

Seattle, WA

Seaweed is a good natural K source along with plant growth hormones and regulators, as well as other trace elements.

Nature’s Essence Soluble Seaweed Specifications
Derived from Ascophyllum Nodosum

Nature’s Essence SEP    
Typical Characteristics    
Appearance    Brown/Black Granular    
Odor    Marine Seaweed Odor    
Total Solids    92%-95%    
Moisture    5%-8%    
Organic Matter    45%-50%    
Inorganic Matter    40%-45%    
Solubility    100% in water    
Fiber    Less than 1%    
Oil    Less than 1%    
Typical Analysis    
Aluminum    Less than 10 ppm    
Boron    50-100 ppm    
Calcium    1.5%-2.0%    
Cobalt    3.5-6.5 ppm    
Copper    20-45 ppm    
Iodine    250-500 ppm    
Iron    250-1000 ppm    
Magnesium    2000-3000 ppm    
Manganese    15-30 ppm    
Nitrogen    0.8%-1.2%    
Phosphorous    100-200 ppm    
Potassium    15.0%-17.0%    
Sodium    3.0%-4.5%    
Sulfur    1.0%-2.0%    

Growth Stimulants: SEP contains natural Cytokinins, Auxins, Gibberellins, and Betaines.

11/9/2013 7:51:13 PM

Deer Park, WI

Shazz-

Congrats on your accomplishment on the scale this year. My classwork and texts have repeatedly taught me that Potassium, once inside the plant, is the most mobile of the nutrients. This implies that if sufficient levels of K exist in the root zone, the plant has no difficulty getting it to the growth tips and other areas of need. Because of this, I do not feel foliar application of K would offer any advantage. Again, this is dependent upon adequate levels of K in the soil.

I believe there is some irony in the term "finisher" as it applies to high concentration potassium fertilizers that are promoted for end of season use. The irony is that if the form of potassium is muriate of potash (KCl), it very may well be that the fertilizer is "finishing" the plant by virtue of the salt damage to the roots and other drawbacks of Cl in the root zone.

If one feels the need to provide a continual supply of nutrients throughout the course of the season, I'd be far more inclined to use a product such as the one Tad listed above as a comprehensive, low dose, balanced source of the spectrum of nutrients a plant needs in the life cycle.

11/10/2013 9:37:28 AM

Napa Ca.

Great post Jose. I was never a fan of the 0-0-25 or the 0-0-50. Thank you

11/10/2013 10:01:28 PM

Joliet, IL

Thanks for the kind words and response Joe. Keep up the great work and and I appreciate your posts as always. Letting more growth to continue at the end of season was great advice some years back and also has contributed to longevity of pumpkin growth in my patch these past couple years. My 1546 added 260 lbs of estimated weight after day 60. This was a first this year. And my half way estimate growth to estimated finish growth was at day 42. Normally I am at day 37 or below in higher illinois heat. Multiple variables involved with cooler year than average temps, but seeing fresh green new leaves being produced all the way to end of september hasto help. I hope to see another drawing of you doing cart wheels when you hit over 1800 like the year you achieved 4 digits many moons ago. Lol. That season in your diary was one of my key motivations to reach that same level. Thanks again.

11/11/2013 9:18:49 AM