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Help! Poor drainage in L.A. yard - to auger, till or other?

7 years ago

I'm in the San Fernando Valley, part of Los Angeles. I'm planning to replace the lawn in my front and back yard with California drought-tolerant plants to help conserve water and help foster a sustainable ecosystem.

I'm trying to follow the "drought tolerant garden guide" put out by LA County, found here:

That guide recommends the "soil lasagna" technique and, since I have fescue rather than bermuda grass, it says I can just add layers over my living lawn without removing it. However, it also says to test drainage first to see if your soil is a brick or sponge. I did the test, and my drainage is bad -- it took over 60 minutes for a 1 foot hole to drain (I dug a few holes, some took longer than others).

The guide says if it takes over 60 min. to drain, you should auger or till to address poor drainage before doing the soil lasagna technique. I've been reading up on augering and tilling, and I'm having trouble figuring out what to do.

First as to augering, I understand I'd make lots of holes in the yard, about 16 inches deep, fill them with sand which has good drainage qualities. My first question is, how do I know 16 inches is enough? My first thought was, "What if my drainage problem (compaction, clay, whatever) goes deeper than 16 inches? Is there a test to see how deep you need to auger to fix your drainage?

Second, as to tilling, I keep reading to remove the lawn first, or the grass seedlings will root and spout if tilled under... However, if I'm going to add "soil lasagna" layers over the tilled soil, do I need to worry about that? I mean, if I can add the lasagna layers over living lawn, then my common sense (which could be wrong) tells me I ought to be able to just till the grass with the soil and then put the lasagna layers over the tilled grass/soil mixture, and the top layers will smother the seedlings same as they would the living lawn, and having the lawn broken up first might actually help the lasagna layers merge together faster (?) I REALLY want to avoid the hassle of having to physically cut out my lawn.

Third and final, as to BOTH techniques, I'm reading negative things about how any form of breaking up the soil by augering or tilling makes it unnaturally loose, and that loose soil then will get wet, and then get over-compacted. So, basically, either technique is sort of like chasing your tail because the solution in the long-term will worsen the problem. But I have not found any third alternative for fixing bad drainage, so i don't see that I have an option. If there's a way to till and take steps to avoid it leading to a future soil compaction problem, and if I don't have to remove the lawn first, I'd probably lean towards that because then I know I'm improving drainage in the whole area, whereas with augerrng it raises questions like how many holes is enough?

Well, any advice on these issues would be greatly appreciated.


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