Hello! Recently I have seen some advice to the effect that it's a bad idea to add sand to clay, because it makes the soil tilth worse, instead of better. I must say I have not had bad results mixing sand into our clay here in Illinois. The native soil here in the Post Oak Flats, is a 2" thick dark topsoil, then clay all the way down to who-knows-where... If you clear land and plow it up, it's white in color. I have put sand on the garden for years, along with lots and lots of compost, and more recently some powdered granite from a monument (tombstone) place. Our soil is friable and easily worked. I guess others have had some bad results, but it's really worked well here, IMO... What say ye?

From what I understand, adding sand to clay gives you something close to concrete. But you said you added sand and plenty of compost. My experience has been that adding compost to clay soils, or any soils, will do wonders to increase soil tilth. Adding some sand along with the compost can help, but I would not recommend adding too much sand to clay in the absence of plenty of organic matter.

I've heard it also depends on the type of sand. Sandbox sand is not what you want. You need sharp builder's sand. I would also say you need OM as well.

Adding sand to clay soil works if
A) You're adding the correct sand in the correct amount and using additional organic material.
B) you're in a small area. Not something to do above 100-200 square meters. When it's over a truckload or two, you should adopt other strategies.
C) you don't mind doing the same thing after a few years. The effect of the sand is limited in time.

From my experience with clay soil, there is no one-time silver bullet that fixes everything. You have to constantly manage it to get good growing soil via mineral amendments, organic material, and possibly tilling/hoeing. That is, unless you're adapting the species to the soil. The geological and climatic conditions that gave you clay soil in the first places are not going away because somebody throws something into the mix, in this case sand.

As an aside, I'm currently using sand as an ingredient in a potting mix and it looks like it seems to be working well. Adding compost and leaf mulch.

William

Sand and clay and no organic matter = adobe or cob.

But WITH organic matter it becomes a wonderful thing. The sand lets the roots breathe while the clay hold the moisture.

Potters mix clay with sand in a pug mill to get a clay that will set and hold together well when fired in a Kiln. Adding sand alone will not improve drainage of clays.

Organic matter is what helps loosen clay soils, the minute clay particles will coat the organic matter making microscopic pills which do not bind together as readily as pure clay particles. As you amend clay soil with more and more organic matter the clay particles become less frequent and so less able to bind together, at that point the addition of sand will indeed increase the drainage ability of the organic improved soil. This can be done in a single season with virgin clay soil (no organic material present at the start) but to successfully do so will require a minimum 5 to one ratio of addendums to the starting soil. Any organic material will work for this, composted leaves, composted manures, already broken down mulches, peat moss, rotted soybean meal, etc. but cotton seed meal is one of the best because of the chemical composition of the material, the amount of surface area it provides for clay particle binding is higher than almost any other organic material you can get.

I have created many rose beds (very demanding of being put in very good, loose soil, for best growth and production of blooms) out of red clay soils in one season by adding vast quantities of cotton seed meal, finished compost and leaf molds, these beds perform best if left to meld for a winter. In the spring come back with a second application of amendments and then add 1 part sharp sand, at that point introduction of rose bushes will succeed very well. I have also built vegetable garden beds in a single season that produced their first spring planting using the same methods as for roses. It is always good to do a soil test after letting a freshly created bed have its over winter rest, that way you can make any adjustments to PH and nutrient needs. Continuing an amendment schedule for any soil can really do nothing worse than making the soil better as long as you remember to do a soil test to see where you are and adjust accordingly.