Tucson is known for its hard clay alkali soil, and also for its caliche - a really hard layer of deposited calcium carbonate. We heard that sometimes you need a jack hammer to penetrate it, otherwise your plants will die either because their roots can't go deep enough, or because the water would be trapped and suffocate the roots. Luckily we don't have a hard layer, but we do have some fragmented caliche. You can see it here as the white material in the hole:
Here's a look of the pile of soil we removed:
Because of that caliche-like stuff, we decided to test the soil for drainage, as recommended in a publication about caliche from the U of A. We partly filled the hole with water and measured the level to see if we get 4" of drainage per 4 hours.
It drained way faster than that. Actually, we got to test it again, just in case the water creates an impenetrable layer with the caliche. It drained pretty quickly the second time as well. So yay! We don't have caliche problems! What a relief!
Tomorrow we'll add gypsum to the bottom of the holes, and then mix the soil with some compost we got a huge pile of:
This will hopefully create a suitable rich substrate for the trees to grow, and the gypsum will hopefully make the soil softer.
Just in case you're wondering how we'll get all that compost to the garden area in the backyard, here's the answer :)
Today we also started digging the beds for the vegetable garden. We still have a lot to do tomorrow!
Bridget loaned me a copy of Extreme Gardening: How to Grow Organic in Hostile Deserts by David Owens. I highly recommend buying a copy or borrowing it from the library -- it is full of useful information and hopefully will save you a lot of trial and error. So jealous of your space for a garden!
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