How much water does a clay hold?

Window screen sifted dry clayey soil in Houston, TX that has been fully water saturated and then allowed to drip until no water will drip out of it, will be approximately 37% water and 63% soil by weight.

1/4" screen sifted dry clayey soil in Houston, TX that has been fully water saturated and then allowed to drip until no water will drip out of it, will be approximately 31% water and 69% soil by weight.

Note: There are many different types of clay soils, so if accuracy is important to you, then you should test your clay.

Answer 1:

It has to do with porosity; which in turn has a lot to do with particle size and the way particles pack together.

In a sand, the particles are relatively large and rounded in shape.

They tend to pack together with a lot of space between them, for water to run through. The larger the particles, the greater the spaces between them (think of a container of marbles).

Clay, on the other hand, is composed of tiny particles that are platy, and they tend to stick together, making it difficult for water to pass between them (think of a pile of playing cards, all lying together).