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On top of Brush Mountain, Pa.

I have been looking at a lot of soil test results and the various recommendations by "the Experts." I was wondering what some of you consider to be the target for phosphorus you are using? Some have levels that are very high while others seem quite low. Phosphorus in high level can tie up Zinc. Solomon recommends the phosphorus target level should equal potassium. This is a lot of phosphorus, maybe 300 to 400 pounds or so pounds per acre in some instances. If you look at IanP's soil test his level averages around 200 while others are even lower. What is the target level you are using and are you balancing it with your potassium target level?

4/16/2019 3:35:34 PM

Colorado

I think ph is more important than a target level.Under 7 ph is good,6.5 would be ideal for optimun phos availability.

4/16/2019 4:14:17 PM

Oak Grove, Mn

Phosphorous can also inhibit myco. I do not have the number right off the top of my head, maybe someone here remembers it. If not, I can look up my notes later. I think best to keep phosphorous on the low side, grow your microbiology, and not worry about the antagonism of phosphorous on the other nutrients, and still not be starving the plants of P

4/16/2019 5:37:37 PM

Morgantown, WV

Ian is very reachable. If you have questions about his soil, anyone, send him an email. He is a wealth of information that is ready for harvest, should you know which fruit are ripe.

4/16/2019 8:41:02 PM

On top of Brush Mountain, Pa.

Dustin, I don't have his email address but I am not certain he wants to be bothered.

4/16/2019 11:07:52 PM

Grittyville, WA

I do not trust Solomon he makes mistakes as frequently as the rest of us. I would not want my potassium as low as phosphorous and I'd worry if it was as high as phosphorous. Things might grow ok but I wouldnt call it balanced. In favor of it though: bnot has used high phosphorous for targeted results with tomato blossoms. I cant answer the specifics.

Since you probably would like heavy hitter advice not mine...

The availability is what matters in terms of myco. A rock phosphate would be less available and not affect myco even if the total tested high. I hope thats correct. (Heard correctly. Remembered correctly. And restated correctly.)

4/17/2019 3:18:35 AM

Oak Grove, Mn

I have used high P and K for megablossom formation with tomatoes. This was in hydro though. After the initial blast, I could flush the tank and it get it back to a normal ratio. When I tried it in soil pots, the plants suffered from not being able to flush. Last year, in my outdoor garden i had 60ppm of phosphorous. That seemed a good number to me. I am not a heavy hitter but still improving year by year.

4/17/2019 6:32:00 AM

On top of Brush Mountain, Pa.

If you look at soil test results, in the last 4 soil tests by the Pattons,over the last 4 years, who grow huge pumpkins, the phosphorus levels have always been on average around 90 ppm and their potassium levels, on average around 450 ppm. Of course they also have a high CEC with recent ones nearly 30. Solomon suggests that P = the target level of K and then varies the target level of K based on CEC. Solomon's target level for K with a CEC of 30 is 253 ppm and so the recommendation for P would be 253 ppm, a huge difference from what most growers are actually using, people like the Pattons who are at around 90 ppm.

4/17/2019 8:00:43 AM

On top of Brush Mountain, Pa.

Doesn't anyone have anything at all to say about what they are using for their target levels of Phosphorus and, for that matter, Sulfur too.

4/30/2019 5:27:21 PM

Oak Grove, Mn

Maybe no one really knows Marv. I know you are pushing new territory in all your research. I will stick with my 60 ppm P, until someone convinces me that is not the right number. My ideal soil is 60 ppm P, in a sandy loam, with all the rest of the numbers balanced around that one. I am just a little grower though..please..no one follow my advice.

4/30/2019 5:37:28 PM

Oak Grove, Mn

Where are the heavy hitters....i would love to see a debate, amongst the 2k growers.

4/30/2019 5:39:47 PM

Grittyville, WA

Daletas was off the chart for sulfer like 600 ppm. Ive had good results at around 200 ppm phosphorous and I believe the wr squash was near that ppm. Im just quoting my memory, which is not to be taken as fact.

4/30/2019 5:39:59 PM

Grittyville, WA

I thought I applied a lot of calcium sulfate but it may have washed out of the soil my plants look deficient. So whats perfect one moment is gone the next... Its always going to be an uphill effort.

Most growers trickle feed thats the "in thing" so who knows if soil levels even matter. You could trickle feed large amounts of npk etc... Amounts that would burn roots if it was all applied at once. I guess you not happy with your results Marv? I am sure there is a perfect balance for everyone. If only we could find that perfect balance... That would be great... We could double or triple our results???

4/30/2019 5:57:01 PM

Grittyville, WA

The heavy hitters publish a lot of info in the newsletters. They dont seem to feel a need to debate.

4/30/2019 5:59:46 PM

Oak Grove, Mn

hmmmm....sorry, i am up to 5 hh emailed so far...seems to me to be a simple? question. I might have only another 20 hh to contact....I will remember...come Vegas

4/30/2019 6:09:43 PM

On a cliff in the desert

I looked at Steve Deletas' soil report after amendments last spring. His P was 120 which is high, K is 891, Ca 3547, NO3- was 48, Zn 12, S 885, and Mg 379. PH was 7.0 We know what kind of season Steve had last year.

4/30/2019 6:42:30 PM

Oak Grove, Mn

my emails have been...if you were starting on the sahara desert. And you had to set a base nutrient and balance off that base...what nutrient would you choose. It may be that P is not the base nutrient. We all know...you can balance the nutrients at extreme levels. Starting from the sahara...which is the first target nutrient?

4/30/2019 6:53:55 PM

On top of Brush Mountain, Pa.

Wile: Are we talking PPM or PPA?

4/30/2019 7:51:49 PM

On a cliff in the desert

ppm

4/30/2019 7:53:18 PM

Partlow,Va

Good topic Marv. My 2 cents

With a PH of 6.5 I am okay with a starting as low as 60ppm.A PH of 7.5 like 100. Just remember P stays put, so when you jack it up it will stay up much longer than other nutrients.

4/30/2019 10:14:18 PM

Grittyville, WA

Interesting question bnot. Like if youre going to build a house, do you start with the roof? You could, but it makes a bit less sense to think of it that way. The calcium/nitrogen relationship might be a good place to start. Thats such a good question, we need a soil scientist to give us an expert rundown?

5/1/2019 12:10:06 AM

Oak Grove, Mn

I have just received a well thought out reply from Joe Ailts. He recommends even lower potential P level that could be considered optimum. His starting point is 25ppm. He wrote down his reasoning for these numbers. I can understand his reasoning. He wrote in the email..that I can share his reasoning with other growers. I still haven't moved away from my 60 ppm in slightly acidic soil yet. But with Joes comments...i certainly am not raising my number soon. I will find out in a few days..if my garden is the new sahara.

5/1/2019 7:04:10 PM

Bloomington, IN USA

I recently went through a bunch of hh soil reports, which I presume are prior to amendments.
P ranged from 38-283 ppm.
I had Steve Geddes’ 2018 report with P at 1,448 which must be a typo.
Michael Astera is a soil guru who I highly respect & he says P as high as 350 ppm.
Go figure!

5/1/2019 10:03:47 PM

On top of Brush Mountain, Pa.

After everything read and everything everyone said it is clear there is no one answer. I am going with P = 1/2 K. So, for my soil I already exceed my target value as well as almost everyone else's and I won't be adding any more P to my soil for a good while anyway. It looks like getting the right soil is more of an art than a true science. If you disagree, then tell me exactly how much nitrogen your garden needs and how did you decide?

5/2/2019 8:32:07 AM

Deer Park, WI

Here's what I emailed bnot: I appreciate your efforts to generate dialog on pumpkin nutrient management considerations. The absence of grower input is almost certainly due to a lack of concrete evidenced catered specifically to our hobby. For what it's worth, I place little value on "Grower XYZ grew a 2000lber, therefore his/her soil test must serve as the template of aspiration for all other growers shooting for the moon"

Excessive soil test values of any nutrient that correspond to incredible patch success tell us very little about optimums. simply because a soil with 500ppm of phosphorus can produce a ton pumpkin does not mean that's ideal. it likely implies more about toxic limits but even still, i'd be hesitant to draw conclusions.

Marv has made the comment that he believes the req I make in my fertility guide is low...I respect his opinion and welcome the constructive dialog. I set a threshold of 25ppm as the lower base of optimum. My number is derived from a compilation of university publications on nutrient management for pumpkins. It is true that these guidelines are based on commercial jack-o-lantern/processing pumpkin production and may not translate directly to competitive giants. Even still, its the closest thing to legitimate scientific research that exists.

Further, because the primary way phosphorus can move out of a soil is through surface erosion, I decided to put a conservative value as my baseline. Growers who use the same patch year over year with continual addition of amendments and ferts will most certainly accumulate phosphorus at a higher rate than other nutrients, potentially leading to long term excessive build up over time.

5/2/2019 8:48:14 AM

Deer Park, WI

Another point of consideration- it has been found that 1 ton of pumpkin flesh contains 1.2lbs of phosphorus. Bear with me on some backwards math...if we assume 1000sq ft per plant, and that all phos in fruit is derived from that soil area, then 1.2lbs phos/1000sq ft = 52.3lbs/acre. Divide by two to get ppm = 26ppm. Obviously this does not take into account how much phos is tied up in the foliage. If for argument sake, we double that value, that puts us at 52ppm phosphorus need for "1 ton of pumpkin production". I recognize these are some extrapolations. But they are based on logical assumptions. I like logical assumptions versus gut feelings.

In bnot's hypothetical "sahara sand", i'd start with water as the primary nutrient of concern. :) I recognize the point you are trying to make...if we try to force nutrient management into a linear process, where to start? Its too bad we as humans are wired to linear simplicity. Soooooo much of the world around us does not operate in linear fashion, nutrient management included. I tried to achieve the same goal in writing the fertility guide. No one nutrient serves as a starting point. but in order to be successful, you have to "chunk it out' to identify where clusters of nutrients naturally co-relate. If I were to choose a nutrient where I believe the greatest benefit exists as far as time/attention given, it has to be nitrogen. Its the most dynamic nutrient needed in the highest proportion relative to all other nutrients. If you can master nitrogen management, the others are a breeze. This is true for nearly all crops of agricultural importance.

5/2/2019 8:48:21 AM

On top of Brush Mountain, Pa.

Just so everyone knows, I very much appreciate Joe Ailts opinion and, in fact, I recently purchased his guide, and read it front to back. I can without hesitation that Joe is extremely knowledgeable about soil and soil management and has done a lot to "spread the word." Joe, I am now focusing in on how much nitrogen my soil needs and this is probably the most controversial of all topics. I need to go and read what you said again and then review all of the other information I have compiled and then come up with what will most likely be an educated guess.I believe most growers don't talk a lot about their soil because deep in their hearts they are not so sure what they are doing is right. They feel insecure. And with good reason.

5/2/2019 1:32:34 PM

Oak Grove, Mn

Joe, I am sticking with my 60 ppm P partially because of your backwards math. If it takes 26 ppm just for the fruit, add to it the P in the foliage and also the P in the that the plant is not able to access. I agree that P tends to climb for most growers thru the years. With balancin, all nutrients will rise in response to the increasing P. Balance, I think is the biggest factor. Minimum and maximum values are still to be determined. If you start at 25 ppm...I think to get best results, you would have to amend thru the season with additional P. This is not an uncommon practice...we know how many blossom booster fertilizers are available. I am not saying 25 is wrong..the myco would be very happy. I am just lazy...and don't want to add things thru the season.

It is easiest to think in a linear approach when starting on the sahara. It seems to me that someone might have to have multiple linear approaches for nutrient groups that are not greatly influenced by a different group.

Marv, I know your P numbers...I think that nutrient is not going to be something you need to increase. You might have to grow a decade of 2k pumpkins to drop it down to Joes minimum, or do the easier...balance everything else to it.

Both you and Joe are talking about nitrogen...the one nutrient..I have ignored the most.

Hopefully saturday...will find out my soil characteristics..hoping for pure sand. Probably wont be that lucky and will have to send in a soil sample for testing.

Great discussion on a subject that is so unclear for the best answer.

5/2/2019 7:02:43 PM

Oak Grove, Mn

I should really make a habit of proofreading before I hit the send. Use your imagination to fill in my missing letters and words.

5/2/2019 7:05:11 PM

New Berlin,NY

So I got 6 soil tests done. 1 for each of 4 giant pumpkin plots, 1 for the food garden, and one for misc giant veg. The lowest is 246, and the highest was 517. Is this problematic? Of note, my larget ever by 217 pounds was grown in the 517 PPM.

5/3/2019 12:14:59 AM

Deer Park, WI

The evidence shows that large pumpkins can be grown in the presence of very high levels of phos. No one really knows if there's a threshold at which high levels become a negative. One principle that is well established is that very high phos can limit zinc uptake. experts recommend at 12:1 phos:zinc ratio. At 500ppm, this equates to 42ppm of zinc, which absolutely would be very excessive for this micronutrient (i do no recommend raising zinc to this level). If, however, zinc was raised to this level, not only could it be toxic to the plants, but zinc itself would outcompete other micronutrients like copper and manganese. See how this produces a negative downstream effect? Overdose on one nutrient and you'll be dealing with a lot more complexity in striking balance with other nutrients.

It is for these reasons that the "more on" approach is really bad for giant pumpkins. Finding and striking balance in pumpkin fertility is absolutely essential rather than pouring the nutrients and amendments and hoping for the best.

5/3/2019 8:05:37 AM