why doesn't sulfur stay in my soil?

[mskrieger]

Apr 8, 2016 1:37:24 GMT -5 steev said:

Here in NorCal, the best example is the "Westlands" developments. With subsidized irrigation, many acres on the west of the Central Valley were put into agriculture. That was very selenium-rich soil, needing drainage to toxify other areas. In the current drought, those interests are bitching that they aren't getting enough water; they're among the least senior water-rights claims in the state; fuck 'em; they never should have been opened to Big Ag, in the first place.

What do you mean, 'needing drainage to toxify other areas'? Did the extra selenium leach into other land and cause problems? Out east, selenium is generally in short supply. Though I've heard of over-salted land. Generally, the issue is that the irrigation water itself has lots of minerals in it, and they build up in the soil, right? I'd guess that elemental sulfur might help with that. Rain dances might, too.

[steev]

Much of the water drained from those selenium-rich soils went to places like Kesterton Reservoir; the minerals built up to levels so toxic birds and amphibians were suffering very high morbidity and monstrous deformations; poor construction in that phrase for clarity.

[swamper]

Our soils have very low anion exchange capacity compared to their cation exchange capacity. There are some anions like phosphate that have a high affinity to binding to the Fe3+ and Al2+ edges of soil minerals limonite goethite etc. This is not the case for sulfate or nitrate.

The best way to enhance soils anion exchange capacity is probably to boost total organic content with compost. Look for a good C/N balance and avoid repeated manure applications which can add too much phosphate to soils. There is evidence that too much phosphate can harm the plant root - mycorrhizza connections. Too much P accumulation is very difficult to mitigate.

Conventional elemental soil testing is valuable but may not tell a complete story of what nutrients are plant available and easilly assimilated.

A light application of gypsum might help boost sulfate, but dont overdo it. A healthy organic carbon rich soil might not need as much S to satisfy your plants as you might think.

[mskrieger]

Apr 19, 2016 5:09:51 GMT -5 swamper said:

Our soils have very low anion exchange capacity compared to their cation exchange capacity. There are some anions like phosphate that have a high affinity to binding to the Fe3+ and Al2+ edges of soil minerals limonite goethite etc. This is not the case for sulfate or nitrate.

Thanks, that explains a lot. My soil is always fine for phosphate. I take it that phosphate binding to the Fe3+ and Al2+ on limonite and geothite is still available to plants?

I don't ever have nitrate problems, except in early spring when the temperatures are cool and heavy rains temporarily leach the nitrate away--as soon as it warms up again and the organic matter decay starts up, the plants (mostly garlic seems to be sensitive to this) green up nicely. Takes just a few days.

Sulfates are my question. I need to find a good strategy to figure out if my plants would do better with more, or if the current situation is good. 

[swamper]

Plant availability of nutrients like phosphorus that have low solubility is enhanced by root exudates and naturally occuring mycorrhiza in healthy soil with high organic content. Mycorrhiza hyphae can stretch 200 meters or more per gram of healthy soil. Reduced tillage will improve soil health and oxygen diffusion, and conserve organic content.

Need for more sulfate is probably crop specific. What are you growing that you expect to possibly be deficient?

[steev]

While I agree that reduced tillage encourages mycorrhiza, on my farm the native soil is utterly organic-deficient, so I'm stuck in a process of soil-amendment to remedy its native deficiency, as well as 70 years of extraction, with little return; further, I prefer never to leave bare soil, as the intense sun tends to burn the OM out of it, while the breeze sucks out the water. Besides which, I separate my planting lanes with tree-lanes that are utterly un-tilled, so the mycorrhiza is somewhat undisturbed.

Clearly, improving this situation is a lot of work, but I think the results are becoming striking, and the more I can do now, the better off I'll be when I'm less vigorous, a future that looks increasingly inevitable.

[swamper]

I'm wondering on my relatively small garden about the pros and cons of a lasagna / sheet composting gardening style with respect to conserving nutrients, and also carrying over pathogens. I generally don't have enough time or space to get cover crops established, since I mainly grow tomatoes and peppers that yield up until frost. I'm looking at a dense mt of chickweed in some areas that were bare in the fall. I added a lot of chopped oak leaves in the fall which are slow to decompose. If anything my pH is high, so I'm not worried about acidity, but they might tie up nitrogen when they break down.

[steev]

Yes, those oak leaves are long-term, lasting acidity; chickweed, while useful as a pot-herb, is not much of a problem, garden-wise; perhaps you have ashes or other mild alkaline material which would counteract the acid leaves.

[mskrieger]

so, here's my thinking on the lasagna-style gardening for you, swamper--your garden is in the middle of the woods, and doesn't get particularly hot. If it's anything like mine, it's already got 6%+ organic matter in the soil (do you know?) So my thinking is:
1. you probably don't need more organic matter
2. yes, it will probably tie up nitrogen
3. it might throw the balance of nutrients in your soil off balance (depending on whether you believe that there's an ideal ratio--I know some folks do, some don't...)

on the plus side, mulch would protect the soil in all kinds of ways. And your kitty posse probably means there's no rodent problem. Then again, do you have slugs and more micro-pathogen issues that might live on and on in the mulch? If you do have slugs and disease issues, I would say the mulch isn't worth it.

If you don't, then go for it, but avoid high carbon stuff, and maybe grab some bagfuls of seaweed and seagrass hay whenever you're down by the coast. They'll enhance your mineral profile and won't bring in land pathogens.

As for your question re: my sulfur concerns: the one year I added elemental sulfur to the garden soil, I had zero disease problems. Everything grew spectacularly well. Also, sulfur (aerial spray) eliminates the sour cherries' fungal problems. I don't yet know whether soil application will help them--just top-dressed around them with gypsum for the first time last fall-- or whether it's purely the topical anti-fungal action. (I don't relish spraying sulfur or bordeaux mixture every year.)

I love to have faith in the mycchorhizae but if the element ain't there (or in not enough quantity), no amount of magical fungi will be able to provide. So that's why I think about sulfur.
--
As you can tell, steev, we have a totally different situation that you! Sounds like you're doing the right thing for your farm. Except I'm surprise the tree-lanes don't suck up all the water in your soil (your primary issue, right?)

[steev]

I think the trees are pretty deep-rooted now; the weeds I throw into the tree-lanes conserve moisture there very well, besides contributing nutrients as they decay; any shallow roots that invade the planting-lanes get tilled out regularly; trees or no, I have to irrigate my veggies if I want to have any; I think the veggies get their share before the water sinks to the trees' roots, mostly.

[swamper]

I am grateful for your bringing the potential issues of sulfur deficiency to my attention. I just ordered a bag of sulfate of potash. I will try a little supplementation to see how much it helps. Without giving it much thought I have used some gypsum and also watering young plants with epsom salts while they are still in their containers.

Today is the deadline to place fedco orders from organic growers supply for shipping to the Simsbury Depot. I will save substantial shipping costs.

Another anion that is a serious concern for me is borate. Boron deficiencies are very common in this area especially in sandy soils with elevated pH. Necessary quantities are very low, a couple of ounces of boric acid applied now to my roughly 2500 ft2, before plants are established is adequate. I dissolve the boric acid in hot water, then use a Hozon Brass Siphon Mixer to water it in around the garden.

Yes I need lot more organic matter. My soil is very poor, ranging from 2 to about 7 percent organic content depending on location where I take the sample. I have been improving that but still have a long way to go to reach a healthy equilibrium. I want to be at 10-15 % in the greenhouse this year so have been adding compost to the two 4 x 20 beds. When I'm done raising seedlings one side will be chiles and the other dwarf tomatoes this year, planted directly into the ground and mulched with chopped straw

I agree that maintaining an appropriate C/N ratio is important.

I do have potential meadow vole issues. Populations seem to explode in late summer early fall, in some but not all years, despite all the wild and feline predators. I'm anticipating some rodent population increases due to the extraordinary acorn crop we had last year. I've never seen anything like it, and I do have large red oaks that drop acorns directly onto my garden. When I planted garlic last year I tilled them in and had many more acorns in the bed than garlic cloves. That will be interesting...

The other concern I have with deep mulching is that racoons dig through the mulch very aggessively looking for earthworms. I have a good population of those wiggly night crawler sized annelids that seem to love to live under things but just above the soil horizon. Racoon disruption has definitely hurt my shallot and potato onion yields. Garlic and tomatoes seem less susceptible but... At some point I might need to consider a better electric fence / lower to the ground.

[mskrieger]

Hm. Some New England gardeners consider meadow voles to be the bane of their existence. I'd tread carefully with the deep mulch. You might do better just importing a lot of manure--seems like there'd be plenty in your parts?

Simsbury is a strange place. I picked up from the depot there earlier this month. Drove through rows and rows of bucolic McMansions owned by insurance executives and then suddenly BAM! there's a rough and ready New England farm. The folks there were helpful but...rough. Yankees in the traditional sense. I was surprised.

[swamper]

Nonono, a lot of manure will elevate phosphorus beyond the levels where mycorrhiza and roots stay connected. Fish meal and emulsions, leaf compost and yes some composts that include manure for me. Check this reference to start: Mycorrhiza and soil phosphorus levels Curtis E. Swift, Ph.D. Area Extension Agent (Horticulture) Colorado State University Cooperative Extension Tri River Area

[mskrieger]

Oh. I did not know that about manure, swamper. Thanks. And no wonder folks in depleted soils elsewhere like it...makes sense.

What are your thoughts about Calphos? (Soft calcium phosphate with colloidal clay). I was going to add it as a small part of my calcium additions (Fedco advises it as part of the soil prep for new fruit trees planted in the Northeast.) I don't think the phosphate is immediately available--it'll take a few years of microbial action to break down. And I like the idea of adding a little clay. My soil could use it.

[swamper]

If your soil test indicates you need phosphorus, the soft calcium phosphate with colloidal clay sounds like a good choice. Calcium and colloids will both aid soil structure. Flocculate those colloids! And of course, adding more organic matter, and tilling less, will also help with both soil structure and keeping those nutrients plant available.