East Facing UK Garden + Clay

[Jeff Layman]

LoL! I'll have to remember that one.

[Higgs Boson]

Cites, please? I am interested in following this up.

TIA

HB

[Brooklyn1]

East facing UK garden:

[David Hare-Scott]

The reason is that clay contains a lot of colloidal (ie very very small) particles that have a high surface area and a surface charge. This has two consequences.

One that they bind water, this accounts for behaviour of clay soils in that they swell when wet and shrink when dry. So a soil with a modest amount of clay will hold water much better than just sand or pebbles whose surface area is much smaller and don't bind water. If you have a reasonable amount of clay this is advantageous to growing, especially active annuals like cucurbits that wilt on hot days if the soil doesn't supply enough water. In my case I have another benefit that the solid clay sub-strata acts a reservoir evening out the erratic rainfall of the region. It takes up water during wet spells and gives it back in dry.

Two that clay binds minerals. The cation exchange capacity and total exchange capacity is much higher than sand. So clay soils don't leach minerals nearly so easily and stay more fertile for the application of a given amount of fertiliser than sand. The disadvantage is that if you have undesirable minerals such as sodium ions these will bind and displace desireable ions like calcium, magnesium etc. This sodised soil is unfertile and very hard to remedy.

Provided you take care not to work it when too wet or too dry and deal with drainage issues soil with a reasonable amount of clay will be more productive than that with very little or none. I think Billy has some tables of the desireable amount of clay in garden soil.

David

[Higgs Boson]

(Awed) I sit at your feet!

Question: Why equate clay to sand? Isn't that going to extremes? My soil is, AFAIK, a good loam (I see that term is still used). The clay- ey (adobe) soil characteristic of this area has been greatly modified by application of various Good Things over time. I inherited pretty good dirt from the sellers [censored] years ago, and have continued to apply compost and worm castings, as well as small amounts of Other Stuff, so it's nice and friable.

[Jeff Layman]

Try here:

quotes: "Clay soils have over 25 percent clay. Also known as heavy soils, these are potentially fertile as they hold nutrients bound to the clay minerals in the soil. But they also hold a high proportion of water due to the capillary attraction of the tiny spaces between the numerous clay particles."

"Sandy soils have high proportion of sand and little clay. Also known as light soils, these soils drain quickly after rain or watering, are easy to cultivate and work. They warm up more quickly in spring than clay soils. But on the downside, they dry out quickly and are low in plant nutrients, which are quickly washed out by rain. Sandy soils are often very acidic "

IME there are certain areas of sandy soil in various parts of the world all well-known for nutrient problems. I believe the Pine Barrens in NJ have a very select flora, and most certainly the lateritic sands of Western Australia are extremely low in phosphates. So much so, in fact, that if normal (balanced) fertiisers are used on Proteaceae from this region you might just as well have given them a herbicide!

[David Hare-Scott]

Equate no, contrast yes. Yes they are extemes, I said that to illustrate the difference not to recommend either. They are ends of the spectrum in particle size but also in minaral composition. Sand is largely silica which is almost inert with respect to water and minerals. Good soil is neither extreme but has both (as well as organic matter) avoiding the drainage and workability problems of too much clay and the poor water and mineral holding power of too much sand.

Have a look at this:

shows the situation in three dimensions instead of the two that I used. It also has some practical tests so you can work out what you have. It is well worth learning and performing such tests on your soil.

D

[Billy]

Here, 70 miles north of San Francisco, we have heavy clay. We scratched at it for years before getting serious. The final solution was tilling in sand (probably < %5), and organic material. On this was planted rye grass, and buckwheat, which break-up, and fills the soil with an amazing amount of roots. Lastly, we keep the beds mulched, which allow the worms to do most of the heavy work of turning, aerating (good soil is 50% air spaces), and draining the soil.

For sure, plants like sequoias, oak, bay, and manzanita can punch through the clay, but east of here in the town of Sonoma, there is impenetrable hardpan (clay) a few feet below the top soil, which can prevent perennials from finding the water they need.

Gotta work with wha'cha got.