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michael357

After further thought on the Fe problem

Michael
12 years ago

The crux of my apple orchard problem is the calcareous soil and pH 7.3 which is no doubt causing Fe deficiency. It is apparent that the best approach is to drop the pH down to maybe 6.5. to drop the pH in an orchard is an interesting challenge, I'd like to broadcast and incorporate elemental Ag. grade S (cheap and readily available) but that would need to be incorporated to work, right? ammonium sulfate would be the N source of choice to use (it'll help drop the pH) but not much can be used or rank growth will result.

I could fertigate with sulfuric acid to get the S down into the soil profile but don't care to handle the stuff any more, been there, done that a-plenty.

So what's a body to do? I'm stumped at the moment.

Oh BTW, what analytical method is used to determine soil %calcium carbonate? I'm wondering just because it occurred to me that my freak'n calcareous soil's ca carbonate is going to have to be determined and accounted for when calculating the amount of S that will be required to drop the pH.

Good night!

Comments (12)

  • jean001a
    12 years ago
    last modified: 9 years ago

    The folks at your county's university Extension Service office likely know the preferred management for soils in your area. Contact them.

    Use this map to locate your office
    http://www.csrees.usda.gov/Extension/

    Here is a link that might be useful: locate your county's Extension Service office

  • gargwarb
    12 years ago
    last modified: 9 years ago

    The method for determining the exact % that I am most familiar with is the Calcimeter Bernard method.
    But, to be perfectly hones, I almost never use it to determine sulfur requirement. I typically just use a qualitative lime content. Have the lab put a few drops of 30% HNO3 and call lime absent, low, medium or high based on the amount of effervescence.
    You can get an exact number but with the variability in the soil and the way sulfur is applied, in most cases, it's like doing surgery with an axe.

    You mentioned sulfuric acid.
    If you don't want to use sulfuric acid because of how nasty it is, you might want to consider phosphoric. You have to use more but it's cheaper so the cost is pretty similar. Another, less aggressive, option is N-pHuric, which will also give you some nitrogen.

    If you want to use fertilizers to push the pH down, ammonium sulfate is good but sulfur coated urea is another option. Since it's not real practical to incorporated in an existing orchard, you can loose some N to volitalization, even if you water it in. That's more likely with ammonium sulfate than it is with sulfur coated urea. The sulfur coated urea is also a slow-release nitrogen source and requires less frequent application.

    Getting back to the iron: Have you considered chelates? Even in calcareous soil, you can have pretty good success with even some of the weaker chelates like dtpa or edha.
    One other thing to consider is manganese, which can often be masked by iron deficiency and vice-versa.

    It's really common in calcareous soils to be deficient in both. In fact manganese availability decrease to much greater extent than iron when lime is present. In fact, if you apply chelated iron and chelated manganese on the same calcareous soils, you could have half of the iron tied up in a month or two. Most of the manganese will be tied up within a few days. That's even if you're using the big-guns chelating agent eddha.
    What I've had success in similar stubborn situations in the past is having the grower push manganese and iron chelates through the irrigation.

    In any case, it will be very challenging and time consuming to adjust the pH in the root zone in an existing orchard. If you're feeling experimental, try augering a few holes around the drip line of a tree about 8 inches deep and packing them with cheltated iron and manganese with a little nitrogen to help with uptake. Or, maybe use iron sulfate and manganese sulfate (or even Sprint 330+Mn, which is chelated iron combined with manganese sulfate).
    Every year I tell myself I'm going to start a trial doing this but I never have time and I'm dying to see how it would work out.

  • gargwarb
    12 years ago
    last modified: 9 years ago

    I keep hitting "submit" instead of "preview". Please ignore the types and bad formatting. Also, I wanted to add in regards to pushing the chelates through the water, that's a constant feed situation rather than a one shot deal.

  • gargwarb
    12 years ago
    last modified: 9 years ago

    Also, I meant to say "Even in calcareous soil, you can have pretty good success with even some of the weaker chelates like dtpa or edha."
    ...when the pH is relatively close to neutral. For example, your pH of 7.3 compared to a pH of 8.0.
    And, I should have made clear that I was talking about iron more than Mn. relatively infrequent iron chelate soil applications can be a lot more effective than Mn would be. The Mn in the irrigation water has been the real key in my past experience. To an extent, the iron chelate can go either way.

    Jumping in the car in about 20 minutes for a road trip. I'll try to check this thread from my laptop in hotels but if I don't get a chance...good luck!

  • Michael
    Original Author
    12 years ago
    last modified: 9 years ago

    Thank you Jean: our state's extension is pretty much non-existant out here in the sticks and geared heavily toward the grain production. One of these days I hope to begin forming a relationship with one of the soil scientists and or agronomists.

    Gargwarb, thank you too for sure: let's see, I've been accused of over thinking my horticultural hobbies but can't help myself after over 30 years of schooling, field and lab work. Being that the free lime is considered "Hi", wouldn't it still be a good idea to get it quantified better than just using a hi, medium, low test when trying to drop the pH ? I know that the free lime has to first be accounted for and neutralized first in order to begin lowering the pH so it just makes sense to me to do the test and calculation to determine how much material (i.e. S) will be required to get that lime neutralized so the 2nd part can be accomplished, lowering the pH with more material.

    Definitely considering EDDHa chelated Fe (Sequestrene 138) for fertigation but as you know that doesn't solve the problem for very long, I'm trying to nudge the soil along for the long term by dropping the pH and will utilize the chelated Fe for the near term until the soil turns around.

    I've handled plenty of concentrated acids over the years and just prefer not too any more, one little lapse of concentration or error in judgement and OOPS, bad things can happen. To be honest though, the concentrated acids would make fertigation much simpler process wise.

    The Mn vs Fe conundrum is a buggar for me still, my trees aren't big enough yet to get enough leaves of leaf tissue sampling and won't be for at least a few more years; as you point out, then there is the results interpretation.

    And just to add another to the ointment, I have to inject acid into my irrigation water to deal with the high bicarbonates which would otherwise make the micros. problem even worse. That problem isn't too difficult and could be made easier if I chose to go with, you guessed it, Conc. H2SO4. Now don't laugh, I use vinegar to drop the pH to 6.5 via a Hozon, somewhere around 800 ml vinegar in 5 gal. water delivers pH 6.5 irrigation water at the hose end. No, vinegar isn't cheap but, hey it gets the job done and I can get it at the grocery store! A 50 gal. stock tank would be a whole lot simpler though and a Mazzei injector would work better also.

    Hope you enjoyed yer road trip. Hope I didn't forget any points you made above.

    Oh, yes, I did think about SCU vs amm. sulfate but am leaning towards the later due to it's ease of application and far better placement (downward in the soil profile) via fertigation.

    Jeez, maybe I should just stick to vegetables and raspberries, never seen any micro deficiencies on any of them.

  • fortyonenorth
    12 years ago
    last modified: 9 years ago

    I don't mean to hi-jack your thread, but could you explain the advantage of the chelated iron and/or manganese vs. simply using iron sulfate or manganese sulfate? Is it that the chelated option will be more available in hi pH soils?

    In terms of lowering the soil pH. Have you considered vertical mulching? I haven't tried it personally, but I've read where it is an effective fertilizing technique for orchards and other established plantings.

  • gargwarb
    12 years ago
    last modified: 9 years ago

    I've been accused of over thinking my horticultural hobbies but can't help myself after over 30 years of schooling, field and lab work.
    Oh trust me. I know what you mean. I do precisely the same thing with my hobbies. For me though, the daily grind has taken most of the "wow" out of plants and soils unless I'm dealing with something new and exciting. Otherwise, I just go with what I find to be most practical for me personally. I've found that whether I have a real number or make a good guestimate based on qualitative lime and other factors, I'll come up with a plan that will get us in the neighborhood and after re-testing there will be a little tweaking required regardless of which route I've taken. But, if you're really into it, the precise number would be more fun; no doubt about it.

    As far as pushing the pH down without injecting or ripping out the trees, adding sulfur and starting again, well...those are pretty much the options I can come up with so if you're stumped at least you have some company on the stump. I suppose another would be a sulfur burner, but that won't be any cheaper than the vinegar. I like your stock tank idea and those Mazzei injectors are great for cost and ease of operation.

    You do make a good point about the ammonium sulfate and sulfur coated urea. Either would work. It's just a matter of weighing advantages of one against the other and deciding which will work best for you.

    could you explain the advantage of the chelated iron and/or manganese vs. simply using iron sulfate or manganese sulfate?

    Sulfates are pretty good ways of delivering those nutrients, especially in low-lime soils. That's especially true if the soil pH is only slightly alkaline, neutral or acid. In fact iron sulfate and aluminum sulfate, more than other sulfates, will also bring about some downward pH adjustment in the soil which makes it real nice for low-lime slightly alkaline conditions.

    However, thy iron and manganese will convert to forms that have very low solubility (i.e. iron oxide) relatively quickly in the soil and become unavailable. (I meant to say "the iron" but I prefer the typo in this case)

    A chelate is a molecule that can bond with a cation such as iron or manganese and remain soluble. That way the plant can take up the soluble chelate, metabolize it, and use the iron, manganese, zinc, or whatever.

    One other thing to consider with iron sulfate in particular, if you're dealing with a landscape, is that it will severely stain concrete if it gets wet. In situations where you don't necessarily need chelating for plant availability, you may use a chelate anyway to avoid the staining issue.

    And in conclusion....hurray for free wi-fi.

  • Michael
    Original Author
    12 years ago
    last modified: 9 years ago

    Gwarb: I'm enjoying the discussion on this topic, seems for a portion of GW dedicated to soils there isn't a great deal of focus on them.

    I finally had the thought of going to one of the country's land grant sites who commonly deal with both fruit tree production and calcareous soils, as it happens I used to live there and opted to go with the more familiar.

    CSU had some interesting info. including:
    1) AB DTPA results and suggested Sequestrene 138-Fe app rates in lb/sq. ft.
    2) the suggestion to not bother applying Zn to the soil but instead do a foliar spray with Zn sulfate just prior to bud break, interesting indeed.

    For grins I looked up MSU and U of VT's leaf tissue data and found not as much difference as I expected, maybe they borrow each other's table values, beats me.

    I snickered when you wrote about tearing up the trees and starting over AFTER starting off on the right foot dealing with the soil. When people around here ask me about planting a fruit tree I jokingly tell them to start when you are young. Between the mistakes made with the soil, pruning, pest control and cultivar selections you may be starting all over more than once.

    Maybe in my next life I'll major in Pomology at school and start the orcharding MUCH EARLIER.

    Methinks the amm. sulfate will be a very good choice for an N source as it will also help to some extent with the pH issue. On that topic, one question, I know the amm. sulfate will donate H+ ions to drop the pH but am not absolutely positive about the fate of the sulfate in that respect. It seems to me that the S will be freed to form H2SO4 which would obviously aid in dropping the pH but to do so it would have to get the H+ from somewhere, from a soil chemistry standpoint the net result would be zero as far as the balance of H+ (and pH) in the soil. What does become of those darned sulfate molecules, I just don't remember?

    Just remembered, good idea in, I think the other post on this topic, the notion of putting holes in the ground around the drip lines and filling them with a Fe fert. like Fe sulfate. It just so happens I have a JMC Backsaver soil probe that would work very nicely for the task. Now for the hard part, what to mix the fert in (if anything) and how much goes in the hole? I would fill the holes from top to bottom (probably somewhere between a 12-18" deep holes).

    Good answer to 41 north's question.

    Hey 41north: never heard of vertical mulching, what is it? I've been heaping about 6-12" of wood chips down the tree rows per year for the last 3 years now, that stuff has been biodegrading to about 1" deep over the summers. I expect with enough years that beautiful dark layer will slowly become deeper and deeper. The worms sure have been busy under the mulch layer taking it down their holes, some holes are big winoug to stick my finger down. One of these summers when I expose one of those big holes I intend to take my 4' long prod rod and gently slide it down the hole to see hoe far it goes down.

  • gonebananas_gw
    12 years ago
    last modified: 9 years ago

    The safest high-concentration acid to be around is phosphoric, though I have no idea where to get it for homeowner use. If you get a droplet on you, the couple seconds it takes to get to washwater is no big deal (unlike nitric, hydrochloric, or sulfuric), it doesn't give off acrid vapors (as nitric and especially hydrochloric), and it doesn't flash-heat the washwater as sulfuric does. Plus it's a nutrient. Still, no one not used to using concentrated acids should handle it.

    (Funny fact or at least lab legend: phosphoric acid reputedly can be made slightly greater than 100% concentration. It is a slight trick with words, but means that you can add some water and it still is 100%.)

  • fortyonenorth
    12 years ago
    last modified: 9 years ago

    Hey 41north: never heard of vertical mulching, what is it?

    Well, for starters, it would help if I referred to it correctly. There is a technique called "vertical mulching," but what I meant to say was "Fertile Mulching." I came across this technique at soilminerals.com. Michael Astera credits Gary Kline of Black Lake Organic in Olympia, Washington. In the document, Michael suggests the "Fertile Mulching" technique is a method to effectively fertilize established orchards, vineyards and other perennial plantings. After looking at it again, it is very similar to the method garg recommended above.

    >> Apply the recommended soil amendments and/or fertility mix to the area under the plant's canopy, out to and a bit beyond the drip line.

    >> Wet the whole area down well, to wash the amendments into the soil.

    >> On top of this spread 1⁄2 inch of quality compost, and if needed several layers of newsprint or a single layer of corrugated cardboard to keep the weeds and grass down.

    >> Wet that down well, then cover the area with 3" of mulch such as straw or ground bark. The feeder roots of the plant will grow up into the newly fertilized zone.

    >> When you wish to apply more fertilizer, rake the top part of the mulch back out of the way, being careful not to damage new feeder roots, apply the new amendments, then rake the mulch back into place.

    >> If rock or clay phosphate have been recommended, it is a good idea to aerate the soil out to the dripline, using a tapered point digging bar to poke a number of holes about 4" deep. Then spread the phosphate and other amendments and irrigate well before mulching. If time and labor are available, the fertility mix may be poured directly into the holes. This will help get the usually immobile phosphate deeper into the soil. A plug cutting aerator such as is used for lawns will also work.

    >> Keep the mulch damp during the growing season if possible.

  • gargwarb
    12 years ago
    last modified: 9 years ago

    It seems to me that the S will be freed to form H2SO4 which would obviously aid in dropping the pH but to do so it would have to get the H+ from somewhere, from a soil chemistry standpoint the net result would be zero as far as the balance of H+ (and pH) in the soil.

    It does lots of stuff. I imagine a very limited extent it does form a little H2SO4 but not enough to make much difference. The Fe will cause some water to go through hydrolosis, breaking water molecules into 2 H's and an O, which drops the pH. With all the H's and SO4's floating around I'd but you would form a little sulfuric acid but not too much and it would be short lived.
    In cases like yours where your neutralizing acid, you're releasing some Ca2+, which will bond with some of those SO4's and you can actually end up making a fair amount of gypsum CaSO4.
    A lot of it will also just leach out, being an anion that doesn't stick to exchange sites.

    Methinks the amm. sulfate will be a very good choice for an N source as it will also help to some extent with the pH issue.

    That's true but so will urea. Rember, that one is CO(NH2)2, giving you 4 H+'s for each molecule. It's not 1:1 but you still get a pretty similar pH shift to ammonium sulfate.

    And yes, it's nice when you get a chance to have a real soil discussion.

  • gargwarb
    12 years ago
    last modified: 9 years ago

    I meant to say neutralizing lime, not neutralizing acid.