Soil Mixture
Question from Peter:
Can I mix cosmetic clay powerder to my very airy perlite/soil mixture to add extra minerals and maybe better water retention. The cosmetic clay is cheap and two pounds is all I’m looking to soil condition with . I’m also planning on mixing in some extra coco coir i have laying around for more water retention. I like my soils airy and have had great success with the soil/perilite mixes and I just want to add a little more and since it’s not all clay i’m not too worried about the clay clogging up anything since it’s going to be used a such a small ratio to the soil/perlite mix. Also I want to add some azomite rock dusst too because it’s cheap too but maybe just clay , I don’t know…
Answer from Pat:
It sounds risky to add the clay since it will percolate down and could cause a waterproof layer. But that is only speculation. You would have to do a properly scientific test by mixing up a small quantity in the exactly same proportions and then planting up pots of it and planting other pots with good quality commercial potting soil and compare the difference. Also empty out the plants and compare root systems.
Mixing up potting soils can be a tricky business, and it’s not always easy to create a good mix. As a general rule clay is not a good thing to add to potting soils.
okay. thank you so much for you help. I will do some experiments with differnt mixes and ratios in pots. have a great new year, happy plantings!
Thanks for replying!
Hi Pat, I may have the same question. I live in Tucson where the soil is caliche, but I have elevated beds and have bought topsoil now for years. But it seems to lose its nutrients easily and ends up being dusty and dry and sandy. I am from Davis, California and lived watching the farmers water the tomatoes only once every 3 weeks because the soil was so clay. I regularly added manure to my soil and tilled it in every year. So I am missing my clay soil. How can I get soil in Tucson that has any substance? I have to water 2-3 times/week to keep my plants moist in this dry heat. Wouldn’t it make sense to have more clay soil and use less water in this desert? I picked up some clay from Willcox, AZ and would like to add it to my soil. It reminds me so much of the soil in Davis. Do you really think that this would turn my soil in to “cement”? And if not, what else can I do to have soil with water retention?
I feel for you with your soil problems. Actually it does not hurt to add a layer of clay on top of sand or caliche but it must be 2 or 3 feet thick and not mixed with the caliche or sandy soil. Mixing the together is what causes the problem.