Green sand, how much to use?

I am thinking of putting some green sand into my garden bed this year, it is roughly 6Ft X 6Ft, and still mostly made of clay soil, although some compost has been added in just recently. But i was wondering how much green sand per square feet would be a good amount to spread throughout? Thanks!

Maybe it depends on how low your soil is in potassium? That's the main thing that greensand adds.

I found one website that suggested this:

"Recommended application is 2-4 pounds of greensand per 100 square feet or 1 ton per acre. For potting soils 5-20 pounds per cubic yard can be beneficial."

http://www.natureswayresources.com/resource/infosheets/greensand.html

So a 5 pound bag would cover 125 to 250 square feet. Since it's slow-release, it seems unlikely to "burn" plants.

In his book "The New Organic Grower" (on page 109), Eliot Coleman recommends 1 to 2 tons per acre (roughly 5# to 10# per 100 square feet) as an initial application (depending on soil conditions), followed by periodic reapplications of 0.5 tons acre in years 2, 6,10,... In addition to potassium, it's supposed to provide micronutrients, too. Based on what I know, I agree that it is very unlikely to burn if applied in excess. Excess does mean $$$ wasted, tho.

I can't buy greensand at a decent price in AZ, so I've never used it.

thanks for the advice, ive also heard that green sand can also possibly make the drainage of clay soils even worse by making it so that it holds onto too much once it finally works its way into those clay minerals. truthfully thats what im mainly after, break up that dense consistency of the clay. i guess i should have mentioned that earlier. (oops).

>> break up that dense consistency of the clay

The three most valuable things you do do are to add organic matter, then add more organic matter, and then KEEP adding more organic matter.

If you have almost enough organic matter to make the clay "livable" for soil life, other things may help a little, like grit and coarse sand. I'm a big fan of adding evergreen bark to improve drainage, because it lasts longer than wood of similar sizes, and absorbs less nitrogen than wood.

It certainly seems that, once you get one crop of something growing that has lots of fibrous roots, those roots stabilize the soil structure and help keep it "open" enough for air to diffuse in and water to perk out.

And once the clay is organic enough to be worth the attention of local worms and other small soil creatures, they will also help keep the clay "fluffed up" (or at least keep drilling air and water channels through the clay).

But without quite a lot of organic matter to start with, and more added each year to replace what the soil life digests, it will revert to airless non-draining clay.

One of the functions of added organic matter is to feed the bacteria, fungi, worms, protozoa and tiny insects etc that make "dirt" or clay into fertile soil. They don't just cycle organic and mineral nutrients into forms that plants can absorb, and maintain the soil structure.

Plant roots need a complex living support system - a community of life in the soil (Google "rhizosphere microbiome"). Soil life helps plants absorb nutrients and resist disease. There is growing evidence that mycorhizal fungi even help plants signal each other about things like the presence of large numbers of insect predators or plant pathogens (Google "rhizosphere communication").

"Feed the soil, and the soil will feed the plants."

http://www.sciencemag.org/content/332/6033/1097.short

Opinions differ about the value of tilling good garden soil. Once it IS good soil, roots, worms and other soil life including fungi may keep it porous and alive without tilling.

But my belief is that, until you HAVE added an amount of organic matter almost equal to the volume of clay, tilling or turning or "fluffing up" is necessary 1-2 times per year to break up the clay, mix in more organic matter and other amendments, and mix in some AIR in the form of voids, gaps, pores or channels between clay clods ("peds").

You can dig, turn, fork or till heavy soil to work some voids into it as you mix in compost, aged manure, coffee grounds, kitchen scraps, shredded leaves or shredded paper. Those voids and channels will let water out and air in until excess water or being walked on compacts it down again.

I imagine that it helps to firm down the soil gently after you fluff it up, and only water it LIGHTLY for as many days as possible, to help it stick together in the "lofted" state.

But if the clay is still gooey and sticky, it can slump down and fill the voids (like pudding settling as the air bubbles rise and leave). It does that rapidly if watered or rained on too hard.

That's why I think that some grit or sand or bark helps clay stay "lofted" or "loosened up" or "retain its structure" when it does not have "enough" organic matter. Grit makes the clay peds a little stiffer so they don't slump down as fast. And if sand or bark fines are partly coating the little clay balls, they might not glue and merge together as fast. Like a powdered sugar coating keeps hard candy from sticking together. And a void that has a few bark fibers and grit grains supporting it is slower to collapse and squeeze the air out.

But whether or not you try to loosen clay with sand, grit, or bark, it needs MORE organic matter until it is SO organic that the humus and fungi and roots keep it "propped up" and keep the worms and other small organisms burrowing.

If you only have 4" of rotted organic matter to start with, I would suggest that you should only scratch it into 4-6" of raw clay. And, next fall, you will need to add almost as much again because the starving microorganisms will have eaten most of the first dose.

Since raw organic "stuff" collapses in size by a factor of 4-8 as it composts, you might need 16-32" of organic stuff to start a bed from 4-6" of raw clay only adding bark, garbage, leaves, cardboard and shredded paper. I think, if you don't mix the uncomposted stuff with the clay that first year, you're following the "lasagna gardening" plan. But ask other people about that, I haven't tried it myself.

Eventually, adding 1-2 inches of finished compost, 1-2 times per year, will maintain living, aerated soil without tilling.

You can even add un-composted mulch or organic material on TOP of good garden soil and let it break down gradually and trickle down gradually to feed the soil biome that keeps the plants happy. This top-dressing or sheet composting is surely the easiest process and many swear by it.

It seemed to me that it would be a slow way to start creating beds from raw clay, so I compost and till for the first 2-3 years.


This message was edited Feb 19, 2014 2:05 PM

thanks for all that info, it sounds like i have been doing plenty of good things there so far--with starting to add in compost and manure and such. I did grow something in there over last summer, and it did pretty decent, but i think some plants were behaving a little bit in a fussy manner because the soil was good enough for them to live in--but wasnt as good as it COULD have been.

Funny that you mention that mycorhizal fungi, as i had just bought a bag of it in granular form for my garden this year.

The bed used to be a former rose bed that mom lost total interest in and gave all the rose plants away to other family members, so she left that plot of soil to me.

Good to know about the evergreen bark, as there are plenty of white pines around here that i could give a good "shave" ;)

Rick's advice about adding organic matter echoes precisely the advice I heard from a University soils professor.

Here are some older photos of my success last year with what the soil composition is made of now, i did give it a good dose of compost over the winter months, and another batch will be ready to put in soon, so it can only do better next time, i didnt get very much squash ( %&#* squash vine borer!) and the eggplant made about 5 or so fruits, all other blooms just would drop off.

>> I did grow something in there over last summer, and it did pretty decent, but i think some plants were behaving a little bit in a fussy manner

Cool, the roots create channels AND fed the soil micro-herd.

>> mycorhizal fungi, as i had just bought a bag

Perfect: add MR and then grow things with lots of roots. You are multiplying the MR and selecting for ones that thrive in your particular soil. Of course, as you improve your soil, different populations of MR will find it most suitable!

Can I find the link to that place that recommends cultivating MR?
http://www.sunseed.org.uk/ but I cant find the PDF ... I found this but it seems like much more work than the old PDF:
http://www.sunseed.org.uk/blog/2014/02/11/mychorrizal-production-bed/

Sorry, got to run soon. If I can find the other article I'll post a link. Basically,

- - -
-l a mixture of host plants are sown - members of the grass and legume family have been shown to be
infected by mycorrhizal fungi easily: maize and beans are a good combination, or millet or other members
of the grasses family with a legume such as lentil.

grow 3 months

At the end of this period the host plants are cut down and all watering stops.

This effectively kills the plant and tricks the mycorrhiza that has infected the
roots into quickly releasing spores. After one further week the roots of the host plants are pulled up,
roughly chopped into 1cm long strips and mixed back into the soil. This soil and root mixture becomes your inoculum.

- - - - -

If you don't mind advice that I never have the energy and time to follow, it is great for soil if you sow idle soil with "cover crops" or quickie "catch crops" of anything that grows fast (clover, buckwheat, fall rye etc etc). The roots open the soil and enrich it, and the tops can be composted or used as mulch right on the spot.

Plus, it is fun watching cover crops sprout and grow. Compared to some fussy vegetables, they are VIGOROUS.

>> The bed used to be a former rose bed

Hmm! I would expect that soil to be pampered and well-fed. But it doesn't seem to take many years for fertile soil to become exhausted.



Thanks, Willy! I echo many other people, when I urge "more organic matter". We had one thread going where we discussed whether ti was even POSSIBLE to have too much organic matter, but the "lasagna gardening" people seem to have proved there is no such thing as 'too much".

>> Hmm! I would expect that soil to be pampered and well-fed. But it doesn't seem to take many years for fertile soil to become exhausted.

Mom never really took much care of it, she really let it go, lol. carpets of small weeds, extremely deep rooted weed trees (we pulled out a crown that was at least 3 inches around from where it has just been chopped back every time something new started sprouting up, no pruning done to the roses, no feeding, etc. It really would have made your average gardener want to yank their hair out, LOL!

took a lot of digging, chopping and yanking to get it clear of all the weed tree roots after the roses were moved, but considering the results last year, and my hopes for this year, it was definitely worth all that

This message was edited Feb 19, 2014 12:54 AM

Impressive!

If it grew weed TREES, the soil must have had some fertility and drainage. You got one good season of crops and and you're improving it continuously.

I bet you and your plants and your garden bed will be very happy together.

yes i was happy with what i got last year. The weed trees were Mimosa (Albizia julibrissin), and they make an absolute menace of themselves, sprouting up practically anywhere that is soft enough for root penetration, lol. There were two really huge ones that were on this property once, both died and now gone for several years now, but the seedlings they had spread around continue to make a pest of themselves, even the 3 inch tall ones making taproots too deep to pull without having to dig.

anyhow, im looking forward to this growing season very much, as i am trying out some new things (easter egg radish, romaine and butterhead lettuce, and some new (to me), tomato varieties)

Best of luck!

To me, the pleasure of seeing my soil improve each year is greater than I get from the crops.