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Drainage test

Posted by ozzz 5b AZ (My Page) on
Tue, May 1, 12 at 11:30

So I did a drainage test yesterday since my soil is a little heavy and seems to stay moist for quite a while, i.e. it seems to hold moisture well .. and maybe too well.

As all the guides suggest, I dug a hole, about as wide as a harden spade on all sides, and about 16-17" deep.

I filled it with water and let it drain. Then I filled it back up with water and watched the results.

Heres the problem, online Ive found four different grading methods... guess what... they are ALL different lol.

The first hour the water level dropped 1.5", the second hour it dropped 1". Keep in mind the hole was very wide at the top and narrow at the bottom.

I filled the hole for the second time at 4:27 PM. At 10:30PM it had about 4" left in it. I went to bed, set my alarm and checked it at 12:30.. it was completely empty.

So my guess is the hole took about 7 or 7.5 hours to empty.

16" / 7.5 hours = 2.13" per hour total.

Ive read that if you drain at over 1" per hour you have decent drainage.

Then Ive read that if the hole takes longer then 4 hours to drain you have poor drainage.

Then Ive read that if it takes over 8 hours to drain you have poor drainage; below 8 is good.

Then on yet another site I read below 6 hours is fast drainage, between 6 and 12 hours you have moderate/adequate drainage, and beyond 12 hours poor drainage.

So what do I have!??

approx 2" per hour level drop on average, 7 to 7.5 hours total drain time (it took about 4 gallons to fill the hole both times).

Can anyone tell me what Im looking at? Im guessing moderate to fair drainage??

Follow-Up Postings:

RE: Drainage test

Fair to moderate sounds about right to me. If you have good surface drainage and don't over water you will probably be OK. To improve the drainage consider planting in raised beds but those are hard to water and salt could buildup over time.

My soil in Amarillo where I grew fruit for 30 years was about like yours. It would take 4-6 inches of water by flood irrigation, the clay would swell up, and drainage would basically stop dead. I grew fruit on it without tree issues.

My current soil 400 miles further south accepts an inch an hour or more forever via flooding if the surface doesn't seal over. So with a grass cover or mulch the water just sails through. For fruit trees in my greenhouse I'd much rather have my current soil. For fruit trees outdoors this soil is too droughty and I'd prefer the clay loam in Amarillo.

RE: Drainage test

  • Posted by ozzz 5b AZ (My Page) on
    Tue, May 1, 12 at 13:53

Thanks fruitnut, you've been a real help on my posts.

My climate is pretty dry so to be honest as long as my drainage isnt horrible (based on the above information) I think I like the fact it stays moist for so long. It will help with watering rather then having fast drainage in a dry climate.

I realize drainage isnt the end all, only factor... but its the one I was most worried about.

So this is a relief.

I still wouldnt mind a few more opinions on grading my soil, just to be sure.

Anyone else have an opinion on what they would grade my drainage from the above info??

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