Summer : Clay, Friend or Foe?

Clay is made up of very small, long, flat particles densely sandwiched together to form the deposits you have come to loathe in your garden. It is these long flat particles that make clay an actual benefit to your soil and to your plants.

These particles are negatively charged (ions) so you can think of them as little magnets that attract and hold onto positively charged nutrients (cations) such as potassium , calcium, and magnesium making them available to your plants roots.  So, clay increases the cation exchange capacity (CEC) of your soil.  It also absorbs and holds onto water which is why when you have too much you get poor drainage.

An opposite situation would be to have too much sand in which case nutrients and water would just drain away before they could be used by plants.  People often feel the addition of sand to a heavy clay soil will help drainage.  It may, but if there is abundant clay and the larger sand particles  mix with the fine clay, they can possibly form a sort of mortar.  Now you have a sand/clay layer wrecking your drainage.

The best method, long term, for breaking up this clay layer is to incorporate compost such as soil amender, or fish compost into the soil.  YES, this requires elbow grease or perhaps a rototiller.

By digging in the compost, you are mechanically breaking up the densely-packed clay layers.  Microscopically, you are breaking up the smaller, flat particles with the larger compost particles which get stuck to the smaller clay particles both mechanically and through electromagnetic attraction of the positive nutrients in the compost, like iron filings sticking to a magnet.

Finally, the microorganisms that break down the organic matter in the compost produce a byproduct called glomulin which binds individual clay particles into aggregates. A simple way to think of this is now the tiny flat particles are bound together creating a particle the shape and size of sand.

Remember this is a process that happens over time. Your soil structure will improve bit by bit with successive amendments.

Hopefully this has given you a different view of clay and the beneficial role it can play in your garden, as well as providing a lasting method of improving your soil structure if you are plagued with an overabundance of clay.

  

Happy Gardening