Michael:

It's my understanding that urea has little effect on soil pH, less than ammonium sulfate and way less than sulfur. Furthermore 2.8% CaCo3 is about 100,000 lbs per acre if my math is correct. 2.8% = 28,000 ppm, ppm x 4 ~= pounds per acre. So to lower pH to 6.5 would require enough sulfur to neutralize 50+ tons per acre carbonates. I'm not sure how much sulfur that is but it would be a lot and I'd be afraid to add anywhere near that much all at once.

In soils with free CaCo3, like yours, the usual recommendation is that trying to lower pH is hopeless. It would probably take 20 years and you might end up with pH 3-4 in spots with other spots still 7+.

Zn and Fe deficiency symptoms are pretty easy to tell apart. Fe has the intervienal chlorosis with normal size leaves. Zn gives small leaves and stunted growth at the ends of shoots. I've had some Zn deficency on pluot in the greenhouse.

Chelated Fe applied to the soil in early spring before or at the very onset of symptoms has worked well for me.

P requirements of fruit trees are pretty low. One good application should last quite a while.

The good news is that this site can take unlimited amounts of wood chips, which can turn a marginally neutral soil too acid here in MI, for example. They will provide about 0.1% P and 0.4% K by weight, and over the years, also about 1% N by weight as they enter bacterial decomposition (of course N cycles, so every few years they need to be reapplied, and for the first year you get nothing).

Decomposing wood chips have a pH of about 4.5, rising to neutral as the decay chain completes. By my estimate, 250 tons/acre would get the average soil pH down by some 0.8 units in the top soil when it is actively decomposing. Not a lot, and not permanent, but better than nothing. They will also save you some water, of course. It is always best to apply urea first, then cover with chips, if you have them both, because urea partially evaporates. In my garden, I always dissolve it first to make sure it goes under.

Did you say 250 tons per acre? Uhh isn't that a pretty big project?

Your boron levels look pretty light.

Glib, where did you get those numbers? Woodchips have a neutral affect on soil pH and any acidification occurs only on the soils surface from the humic acids released during decomposition is my understanding and I've been using tons of woodchips for decades.

Cornell shoots for a pH of 7 for apples,not 6.5. However, you don't have to alter much soil to give the trees access to the freed up nutrients from applying sulfur so even a surface application should quickly correct most of the symptoms of excessive pH- especially if woodchips are spread after the application, giving roots access to the soils surface. In other words you don't have to correct all the soil at once. The only issue is when the surface dries out the forming fruit will not get anything from the soils surface so this could be a problem during dry spells. Foliar feeding could tide you over here.

The amount of ammonium (maybe 2 pounds actual N per 1,000 sq ft) that your trees can use will only slightly lower your pH. In the northeast it is not nearly adequate to even sustain a desirable pH in soils prone to a pH in the low 6's. I believe you have to use either alluminum sulphate or sulfur.

The 4.5 is from past notes. I do not have the reference in front of me now. Yes, it would be just at the surface soil. I also went with 250 tons/acre because I saw in my own backyard that 30 cubic yards will mulch only 1600 square feet or so.

Thank you all:

The most extreme (by far) chlorosis I'm seeing is on the 9th leaf Freedom tree, the rest are 3rd - 4th leaf now. I'm such a dope for not getting pic.s of the chlorosis symptoms but here is what I (REMEMBER) seeing - the cluster leaves never show any, it begins following fruit set on the new shoots (only I think) and continues on the new growth up until about mid Summer then ceases on the new growth as it peters out, it starts up again around harvest time and remains until leaf fall. I realize this may have some scratching their heads, my observations and recollections have been sub par and may therefore not make much sense. The leaves on a shoot appear destined to remain chlorotic once they have formed and never recover. I'll do a very good job this year of observation and documentation if it kills me, this is embarrassing.

Fruitnut: aint our soils just dandy! My math, for what it's worth. 2.8% = 0.028, an a.f.s. of soil = 2,000,000 lbs. therefore 0.028 x 2M = 56k lb. of lime in the a.f.s.. I was aiming for a foot deep so we'll go 56k x 2 = 112k lb., 112k / 2 = appx. 56 tons/A, one ft. deep.

I haven't nailed down my S amt. yet to neutralize the lime but am re-thinking the 1 ft. depth to just 6 - 7" for the first year of additions. I've seen the same comments about hoplessness but some are colored by the economic costs associated with adding large amounts of S. I take your point about pH variability in different locations.

I did look at a number of pics. and descriptions of apple Fe and Zn deficiency in leaves last year and couldn't separate the 2 looking at my tree(s) it was frustrating and I figured it wouldn't be all that hard to figure out, I was wrong!

Well aware of chelated iron and may go that route, my first inclination has been to correct the soil pH and lime issues in that they can cause other problems as well. CSU (and others) recommend a green tip Zn SO4 spray for Zn deficiency, I may give that a whirl this Spring on one side of the tree and leave the rest alone, or do the whole darned tree.

H-man: after further reflection over the past few days I agree that I'd best not go for altering the entire soil profile down to a foot this year, probably calculate and amend for the top 6" this Spring then sample 0 - 6" and 6 - 12" next late Fall to see what happened and go from there. If I recall, the wood chips and leaves release a fair amount of Ca when they break down too.

I've gone back and forth over the foliar feeding but haven't tried it so far except a very small trial on the pear tree with Fe EDTA, it burned the leaf margins and the rate and drying conditions were correct. After that experience it soured me some. The N source for me is just a matter of getting the most pH lowering for my buck while adding the N, in retrospect, ammonium sulfate has the highest CaCO3 neutralizing effect of all the N ferts., DUH. I don't expect the miniscule amount of amm. sulfate added to my soil to get the N I need this year to pack much of a punch to the pH but it's a step in the right direction, S will have to do the real heavy lifting on neutralizing all that lime.

My target pH is 6.5, no plans to go below that, no real reason to that I can think of, point taken.

Man I'm starving, thanks again all. there was probably more to write but the stomach has my full attention now.

Michael,

K is a little low, so you might consider a more balanced fertilizer vs. 10-34-0.

As beeone mentioned, your boron is light and apples need boron. I've used 20 mule borax to bring boron up. Just make sure you spread it evenly. It takes very little and is easy to overdo. About 1ppm is what you want to shoot for.

As you mention OM is pretty low, but your wood chips should eventually remedy the problem.

When I started my P was below 5ppm which is too low even for fruit trees. I used DAP to bring it up. The lab I used wanted to see it in the low 20s. As I recall, I used 400 lbs./acre DAP split in two applications.

michael:

Before you apply enough sulfur to neutralize even half the carbonates in the top foot, I think you should consult a professional. I think there is some possibility of harm. I've read recommendations of not exceeding rates 1% or less of what you are talking about. But that's on soils without free carbonates. You soil may eat sulfur without so much as a burp. Actually I'm sure the soil will. It's the trees that might object.

If you try this I'd really be interested in the outcome.

Fruitnut: Where would the harm come from, too high of a concentration of S in a particular location due to broadcast spreading; I.E., roots in the top 1" of soil getting scorched by the sulfuric acid generated or something like that?

I haven't come up with an S rate yet to deal with any amount of the free-carbonates but hope to soon, darned chemistry is my weak subject.

My soil is loaded with free-carbonates (2.8%) and that is the problem, until they are neutralized, the soil pH isn't going down no matter what I do.

Have you ever heard of that rec. for spraying Zn sulfate at green tip?

michael:

I could be way off here but I think the weight of sulfur needed would be about 32% of the weight of CaCO3. I get this by summing the atomic weights of sulfur=32, Ca=40, C=12, and O=16. Sulfur totals 32 and CaCO3 totals 100. I think one atom of sulfur would neutralize one molecule of CaCO3. The end product is CaSO4. One sulfur molecule ties up one Ca molecule as gypsum. Again could be way off.

I'd start out with 1/3 or less that amount.

My soil pH is about like yours but it has little free carbonates. I have added some sulfur to try to correct Zn deficiency of pecan, a very common problem. Not sure if I've lowered the pH any.

Thanks for the thought Fruitnut: I had the same idea of going the atomic weights route for a possible answer but haven't gotten off my mentally lazy butt to do what you did, thanks, I'll check you figgrs and see if we come up with the same thing.

From reading I learned that, until the free-carbonates are neutralized, pH will not even budge with the addition of acid forming substances, all they do is work on neutralizing the carbonates. Perhaps a good analogy would be doing a pH titration in the lab, you keep adding a base solution to an acidic solution in a flask until an end point is reached at pH 7.0. At the end point you get the indicative color change. Past the end point the pH can now go below 7.0 by adding more acid. Think of the stuff in the flask as my carbonate filled soil, all of that carbonate has to be neutralized before the pH can be driven below pH 7.0 with more acid forming substances.

If the flask has a strong base it'll take more acid to neutralize it (my soil) if it has a weak base (your soil) it'll take less.

Anyway, it's fun to bat this stuff around, thanks.

I realize this isn't a perfect analogy but, hey, I ain't perfect, it's my best try for now.

You're right the pH won't drop until you neutralize all those carbonates. This will start in the surface zone of incorporation and leach down from there. My only concern is that the pH might drop too low in places. Could be all wet. The acid may leach down and reach more carbonates with no issues.

Fruitnut: we agree. If I was going to start a new orchard here I'd probably be much more aggressive with S apps. and shoot for neutralizing a good deal of the lime right off the bat, a year or 2 in advance of planting, maybe in another life time. for now I'll live with my mistakes and manage the situation with much smaller additions of S and acid forming ferts. aiming to manage the soil solution and slowly whittling away at the free lime. Hopefully I can get the soil to the point where the S additions won't be needed over the years.

I don't think you are all wet particularly re my situation where the trees have been growing for years now with new 6" layers of chipped tree mulch added every year, no doubt there are many roots near the surface under the mulch that would be susceptible to a high concentration of surface applied S. It would be best to till in the S but I fear tilling up the root systems while tilling and choose not to till.

There is one option of applying higher S rates and tilling it in in the unmulched row middles and perimeters. I'm thinking the roots are going to grow out there over the years and this would be my only chance to make an abrupt pH + free lime change there that will help out as the trees age. Not 100% sure of that strategy yet.

I finally have managed to get the info. I need to calculate the math and chemistry in order to neutralize any given amount of lime based on the lab's %lime result using S and/or ammonium sulfate and/or urea, that has been a real labor for the brain but, whoopee, it's done!!!

Michael:

It's possible, maybe even likely, that you only need to acidify a small portion of the root zone to allow adequate Fe uptake. If you aren't getting chlorotic leaves that's all that matters.

Fruitnut: agreed, that's what I had in mind with managing the soil solution, as you point out, particularly in the root zone. As long as the soil solution is OK there should be no micro. problems even if all that lime is still there in the soil itself. At any rate, that's the way I see it, it's a matter of trying to neutralize all of the lime where the roots are or just making the soil solution conducive to micro. availability.