Anybody make loam? Which type of sand to use to amend heavy clay soil.

According to what I read,  loam is a mixture of sand silt and clay with no firm ratios.  But something like 40% silt, 40% sand, and 20% clay is good.    My soil is heavy clay.  So, I'm going to add sand for my greenhouse beds.  BUT!  Which  type of sand is best?  There's concrete sand or course sand  (a mixture of coarse, medium  and fine grains) that people use in cob or concrete or rock walls  Then there's stucco sand which has is kind of standard and its all "medium grains"   and then there is masonry sand which has a mix of the medium and  finer grains.  Anyway, I'd love to know if anyone has had success and which sand they found works well?  (I'll be adding organic matter too but I want to have free draining soil for the greenhouse this year.    Thanks,  Brian.

Brian,

I am also gifted with very heavy clay, to the extend that I have had to haul in soil (also clay-ish but not as terrible) just to get annual ryegrass to stay alive long enough to provide some roots for erosion protection. Conventional wisdom is to not add sand to clay as an amendment, because the fine clay particles pack around the larger sand particles. It sounds like you are also adding organic matter so that should break it up a bit to alleviate some of the conventional concerns about clay+sand, however I would ensure you had enough organic matter. Following your ratios amending 80% is more along the lines of soil replacement versus amendment, so at that point also consider the cost of purchasing good soil versus the cost of adding sand and organic matter to clay.  

I don't know how big your greenhouse is, but I would imagine cost could quickly become a concern, so I would probably go with the least expensive sand. I have considered buying a dump truck load of sand, probably masonry sand, for use when I amend my annual garden bed. I don't know if I will do this or not, I would also need to get my hands on a lot of organic matter as well. I would personally spend the savings from the least expensive sand option on additional organic matter before I bought more expensive sand.

I lived and gardened in heavy clay for a couple of decades. It's so damn fertile if handled well, but in certain circumstances it makes an impressive proto-concrete (say, a very wet June-July, and a near-drought August-September).

Mine had tons and tons of organic matter, as was obvious when you sunk a shovel into my soil and then into the adjacent industrial farmer's field. But when the stars misaligned and it became saturated and then dried out, it became "cob." I have family members who finally got mad and used a bobcat to dig potatoes in fall.

I was always told that sand amendments to heavy clay need to be very coarse, almost tiny gravel-sized, to avoid the concrete effect. We moved before I could try it, so I can't offer hard experience.

Now I'm in sandy soil, with its own set of headaches. Maybe I need to import clay? Sheesh.

Well, the good news is that  you need less clay to make it right!  And,  I know that at least here on Vancouver Island, in new construction,  they pay to get rid of clay. Cob builders often get it for free.  

Brian,

I too have heavy clay.  But in my case I brought in wood chips, as in heaping piles of wood chips and the soil biota went to work.  Now there is no clear point where the chips end and the clay begins.  Personally I would never dream bringing in sand (greensand would be different) as I am afraid I would make the ground even harder in the summer.  But wood chips break down so well it’s virtually magic.

Eric

I was thinking about doing the same thing myself until I read the assignments in my latest Master Gardener class.  I agree that it seems like adding sand to clay would make a lot of sense. However, my training says that adding sand to clay only serves to create less pores in the soil instead of more, leading to the cemented ground situation I am already familiar with.  I don't need more of that!  
Instead, they recommend adding compost to the soil to improve it.  For your greenhouse beds, based on my experience, I would highly recommend lots of compost.  It adds nutrients and aeration to the soil, and almost all plants love it. It breaks down over time to improve the soil.  For my other beds, I spread lots of arborist chips on them to improve the soil and suppress weeds.  The arborist chips have both fine and coarse material in them, so some of it breaks down quickly and some of it is time released. We moved into this house a year ago and the beds had been very neglected.  We've been putting arborist chips on them since we moved in and everything is so much happier!

I'd advise against adding sand to clay soil. Essentially, you will turn it into more of a "brick" situation. It wont help with aeration, percolation or infiltration. It will be more prone to compaction and end up making a more solid engineering material than soil. But check your soil ribbon test, feel a bit of the soil with copious water in the palm of your hand (slippery? silky? sandy?) or you could pay $50 for a soil particle analysis, but not necessary... chances are you are missing silt, but no worries. Then there's also looking at soil structure, is there any? Does it break up into clods, one solid mass or does it look like a stack of plates? all those observations are meaningful

General Solution: Organic matter, Organic matter, Organic matter (OM)... Increasing the soil organics will help alleviate compaction, while increasing microbial activity, worms, infilt/perc... best ways to add organic matter: green manure covercrops (densely planted peas/vetch/grains/radishes, mustards; while still green chopped and churned into soil, or chopped and left on the soil surface and repeat), and two, copious amounts of compost.  Careful not to work the soil too wet (it will just ball up) and if too dry (impossible to break bricks)...

I'd start in spring with (keeping in mind soil moisture)...  rough up the soil surface, maybe aerate with a heavy tyne fork (without turning soil, try to leave current soil structure), heavy covercrop seed planting and cover it all with an inch or two of good compost. I'd add some daicon radish or a taproot type radish into your cover crop mix that will root break deep into that soil. you could add a light covering of straw on top of all of it to help keep the moisture up.  Its not an overnight fix and it might take a year or two, but you will end up in a much happier situation. You will have to keep up on your OM additions annually or it will revert, but if you keep up the balance, you will have happy adventures.  
Have fun. hope this is useful.