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Although I've been gardening for 30 years I'm still learning. I have very - I would say extremely - sandy soil, pH 6.8, which has been amended annually with compost, peat moss and chopped oak leaves. My gardening focus is on the Ericaceae family, conifers, with some Hydrangeas, Japanese Maples and grasses. I am thinking of using green sand as an amendment, both in established beds and in new bed preparations. Any advice?
Green sand is mostly iron potassium silicate. It slowly releases the metals into the soil.
I use it, also Epsom Salts. Do not use other fertilizers this time of year. Nitrogen produces new growth and the plant will not be hardened off for winter. Avoid aluminum completely (your plants hate it). It is best to avoid Ammonium also. The nitrogen in spring should come from other nitrates.
I know about the negative effect of aluminum sulphate on the roots of rhodies as well as avoiding late fertilization ( nothing past July 1st around here) . I just havn't ever used greensand. Because my soil is so extremely sandy I'm always looking for things to help bind the soil, besides the usual compost, peat, chopped oak leaves and anything else I can work in. My favorite fertilizer for all acid lovers is Fertilome. I find it works better here than Holly tone.
Epsom salts is not necessary here as there is no magnesium deficiency. But manganese is in short supply. Even though manganese deficiency usually shows up in high pH or poorly drained soil I have it in pH 6.8 soil that actually drains a little too well. The symptoms mimic iron cholorosis. I added iron chelates to little avail thinking that was the problem, then an Extension soil test pointed to manganese! Go figure! I sure never expected that!
Anyway, back to green sand. Does it really noticeably help bind the soil?
My local organic nursery recommends green sand (NPK 0, 0, 0.1) for plants and soils that need either potassium or iron but they have not commented on its binding soil properties. However, a web page in that I came across recently mentioned that it was good for binding the soil and also for loosening clay soil so go figure.
Personally, adding compost, humus and/or some molasses to sand would be my long term suggestion as the development, excretion and death of big and small organisms in the soil will help bind soil particles.
I can't thank you enough louis_pr for that link. That's the best description of the properties of green sand I've come across. I think it will be an excellent addition to my excessively sandy soil. The soil here is so sandy that if you sieve out any roots or the stray stone or two, it can be bagged for play sand.
Molasses? Well here I go again learning something new.
I am not into organic stuff as some people are but the idea behind sugars -like molasses- is that they help small organisms feed off the sugars (bacteria, etc) and then these bacteria, their excretions and their dead bodies will slowly help the soil bind. Compost works on the same principle.
Just wondering, how come your soil there in Ohio is so sandy? Is it localized or state wide? I am aware that many parts of the US were once under water so I am not sure that is the reason in your case. In the Dallas/Fort Worth Metroplex, we have tiny few locations around dried up lakes where the soil is sandy because of these lakes that used to be here a long time ago. But mostly, we have limestone or clay soils.
I live in an area that is called the "Oak Openings" (NW Ohio) area. The habitat is Oak Savannah which is globally rare. Sand dunes are a major part of Oak Savannah habitat and my house (whole neighborhood actually) sits right on top of one. The nice part is the natural pH is 6.6 to 6.8 which gives you a very wide latitude of plants to grow. The sand runs 20' deep in most places. Underneath the sand is impervious clay. In a few places ( not around me) the clay is at the surface. The dunes apparently shifted and blew eons ago. The sand is from glacial lake deposits. Now that I understand it and have learned to work with it I love it. But you have to mulch, compost, compost, compost and be especially vigilant with water sensitive plants like Japanese Maples, hydrangeas, ferns etc. Stuff can dry out here in a big hurry. That's why I'm so excited about green sand. If the stuff does what they say, it should be a great soil conditioner.
As a volunteer botanist and field worker for the Nature Conservancy I was one of the last to record a Karner Blue (very late 1980's - early 1990's ) in the field before they were declared extirpated from Ohio. They were actually reintroduced to the Oak Openings area a few years later with stock from a population in Holland Michigan. I love to walk the Lupine when it's in bloom. They can be seen most easily at Kitty Todd Nature Preserve, where they were first reintroduced.
BTW I don't want to give the impression that I'm some hot shot botanist or naturalist because I'm not - Just an eager volunteer who received wonderful training from the Nature Conservancy and the ODNR with the Toledo Metroparks. I was even allowed to go to Holland Michigan and participate in field work there in preparation for the reintroduction.