My basic potting soil that I make consists of the normal recipe of ⅓ organic top-soil, ⅓ pet moss, and ⅓ compost. But no clay. Clay minerals are hydrous aluminum phyllosilicate minerals, composed of aluminum and silicon ions bonded into tiny, thin plates by interconnecting oxygen and hydroxide ions. Clay tends to increase the Cation-exchange capacity (CEC) of the soil. Cation-exchange capacity (CEC) is a measure of how many cations can be retained on soil particle surfaces.[1] Negative charges on the surfaces of soil particles bind positively-charged atoms or molecules (cations), but allow these to exchange with other positively charged particles in the surrounding soil water.[2] This is one of the ways that solid materials in soil alter the chemistry of the soil. CEC affects many aspects of soil chemistry, and is used as a measure of soil fertility, as it indicates the capacity of the soil to retain several nutrients (e.g. K+, NH4+, Ca2+) in plant-available form. It also indicates the capacity to retain pollutant cations (e.g. Pb2+). So I have added some clay to my last batch of potting soil. Comments welcomed.
Looks like a nice idea on paper, besides your mix might benefit extra aeration like rice hulks and perlite.
To make up for lack of clay, most of use rock dust. Granite, glacier, green, rock dusts are popular choices. Some folks also use Azomite. Adding Bentonite is popular with folks that source it locally. Cheers Os
Hiya Os, how ya been bud? That's interesting about the clay. I've bin avoiding it, as it's all over the place here. I guess a little bit added in the garden will help.
Hi ya! A little clay is ok. But ya clay usually means horrible drainage outdoors. I don’t blame ya for avoiding it. I personally would go the rock dust or sand route before I would add clay. If you’re going to play with clay in the soil, I would try a small scale experiment before adding it to beds or something real big. It’s hard to undue in those situations. Cheers Os
thanks for the reply I source my clay from my property and I'm only using it in one pot for now, thanks again
Thanks LashDog OS, I was very surprised to read that rock dust and friends helps for EC. I was adding them for fungi, minerals and macro nutrients, and to make my soil mix more like real soil and less like soiless media. Thanks!
If you source your clay onsite, then there might already be clay in your "top soil," whatever that is. I've found that certain composts can weigh down the soil too, so I second the recommendation of additional aeration amendment, up to 40% in some cases. Since you call it "potting soil" I am assuming it will be used in containers, and those are usually intended to drain fairly well. Without further information, the addition of clay to your recipe would potentially impede good drainage. You'll know as soon as you try and water it. My $.02.
I can make pottery with the clay I got here. I like how it holds on to nutrients , especially having a garden on a slope .
good point, well add some aeration in the next grow, I only flower two plants at a time, just a personal medical grow.