soil rehab post roundup

pegkipSeptember 9, 2008

The fill dirt we purchased for two beds on our property was infested with nutgrass and bermuda grass (and a few other non-native weeds). After much research, angst, and self-flagellation, I sprayed roundup on the entire bed and am in process of removing as much of the plant and root as possible.

I called the local organic nursery and they recommeded I wait one year before planting anything edible in the bed. They recommended the following amendments - biozome, worm castings, compost tea, and a cover crop. I was concerned about the local wildlife eating the cover crop and ingesting any residual poison. I am considering a clover because that is only 4-6 inches and this bed is near my front door.

What do y'all think? I don't want to poison the bunnies... their second suggestion was to plant things that the rabbits would ignore like rosemary or sage, but refrain from using in food for a full year.

Once the soil is healthy again, I'd like to plan an edible landscape. The bed is about 8" raised with an eastern exposure and very large... about 25' long and 8-10' wide. The imported soil looks to be black clay from further east (we're in the edwards escarpment). The bed needs to be somewhat attractive because it is right at my front door.

Thanks so much for your suggestions!

(as an aside - the other bed that is also infested with bermuda that is now going to seed... I am living in fear that the bermuda will jump the bed and get out onto my property which, up until now, is strictly naitive plants. that bed is even larger and was already seeded with native wildflowers. i am clueless as to how to tackle that problem. this bed covers my septic tanks, so is really shallow in some spots and quite steep.)

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Definitely a cover crop, but your local office of you state universities USDA Cooperative Extension Service will be better able to answer which one. Whether any of the other stuff is needed would depend on what you soil now has and they way to find that out is with a good, reliable soil test from the same place, the biozome, worm castings, and compost tea may not even be needed and you would be spending money unnecessarily if that is so. Along with that soil test from your state university, or a recommended lab, dig in with these simple soil tests to see what is there now,
1) Structure. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. A good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top.

2) Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drains too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up.

3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart.

4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer you soil will smell.

5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy.
and to see what, if anything, else needs be done.

    Bookmark   September 9, 2008 at 7:06AM
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kimmsr, thanks! I've sent an email to the local USDA office to ask about the soil test. As to #5 Life... no earthworms. I saw one grub, some very small black ants, spiders, a cricket. That's about it. I think the fill is black clay as I spent quite a bit of time breaking up clods as I was digging out the bermuda and nut grass roots... the native soil underneath is caliche. as I was digging up the roots, the mulch (cedar shavings) was mixed into the soil and there are, of course, bits of bermuda everywhere. The soil was slightly moist in the center of the bed and bone dry at the outer edge.

    Bookmark   September 9, 2008 at 7:27AM
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If I am understanding your question correctly you are asking what to do to your soil to make it suitable for growing edibles after having used RoundUp?

You don't need to do anything at all. Round up translocates from leaves to roots, not roots to leaves. While herbicides such as RoundUp are not part of organic gardening this doesn't mean they turn your soil toxic either. Your local nursery gave you bum info.

Since you are contacting your university extension on other matters, why not ask them about their view on what, if anything, you need to do to the soil post RoundUp use before growing edibles? I would bet money they tell you the same thing I did.

    Bookmark   September 9, 2008 at 10:03AM
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justaguy2 - I posed the question to the extension agent... we'll see what they say.

The agency offers the following analyses:

1. Routine (R)(pH, NO3-, P, K, Ca, Mg, Na, S, and conductivity) $10 per sample
2. R + Micronutrients (Micro)
(routine analysis plus Zn, Fe, Cu, and Mn) $15 per sample
3. R + Organic Matter $20 per sample
4. R + Micro+ Organic Matter $25 per sample

Which do y'all think I should request?

    Bookmark   September 9, 2008 at 11:25AM
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I would go with #4 if you want everything, but personally I would just go with #2. This gives you a pretty complete nutrient analysis so you know what, if anything is excessive or deficient in your soil.

The organic matter part is kind of pointless for an organic gardener since we add organic matter routinely regardless of what any test says ;)

If you will be sending in multiple samples from different areas of your yard you can save some money by going with #1 for all the samples except for 1 sample. That sample should be a mix of all the other samples. Just get the micro nutrient analysis on that one sample since any soil amended with organic matter is incredibly unlikely to be deficient in any micro for very long.

    Bookmark   September 9, 2008 at 11:48AM
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I think you local organic nursery is trying to sell you a lot of thing you don't really need. Don't buy into the scare tactics! In the future, if you run into a similar situation, just spread some clear plastic over the soil surface and leave it be in the hot sun for a week or so. It will cook and kill EVERYTHING, and no chemicals needed.

Roundup breaks down fairly quickly. Usually in a couple of weeks. I would till in a large helping of compost if available. If not, as many grass clippings, chopped leaves, etc. as you can every week for 2-3 weeks, and water heavy. Add a nitrogen source and maybe a little bone meak, and you can plant in about 3-4 weeks.

Technically, it will not be an "organic garden" but there will not be any toxic residue that going to cause any harm to you, your family or the bunnies!

The Garden Guy
Come on over for a visit!

    Bookmark   September 9, 2008 at 7:46PM
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Soalrizing your soil will take anywhere from 8 to 12 weeks depending on how much sun you get. One week will do little.

    Bookmark   September 10, 2008 at 12:43PM
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rhizo_1 (North AL) zone 7

Sheesh, justa hit it right on the head! Your organic nursery folks need some educating!

Solarizing is a rather detailed technique that needs to be done correctly and at the right time of year, it is completely ineffective. Even with everything at its best, the process requires several weeks, as kimmsr says.

    Bookmark   September 10, 2008 at 1:25PM
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