Cover crop for clay soil - please advise

danell(7)April 30, 2011

I live in Medford, Oregon and have non-homongenous soil (dense clay with partial loam). Nitrogen, Calcium, Magnesium, Sulfer and Copper contents are low. I thought to cut back the lawn and plant Diakon radishes and Fava Beans to prepare soil for a border of perennials, conifers, Maples and shrubs. The lawn is getting cut back at end of next week which means I could possibly begin planting mid May. Have I missed the planting time? Should I wait until Fall? Is there something else I could use?

I did have a soil test done but the recommendation was just an application of compost and organic fertilizer - I think I need more to whip this clay into shape. Yes?

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As a side note I thought I should mention that last Fall I layered cardboard, peat moss and compost over narrow existing beds - thus the now existing non-homogenous soil. The area under the grass that was not layered is likely just clay. Don't know if this helps answer my question but thought I should mention it. Thanks - looking forward to your replies (smile).

    Bookmark   April 30, 2011 at 6:33PM
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Hi Danell,
I got nothing for you ;-)
But I wanted to say "HI"
Finally, Someone close enough to me ,that .... UM.... well, I don't know what.... never happened before ;-)
Glad to have you onboard... Someone around here ought to have a reasonable answer for you...
I only grow Food (for the FoodBank), so don't know anything about non-edibles ;-)
C-Ya around ! !

    Bookmark   April 30, 2011 at 7:16PM
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To make that clay into a workable soil you need to get the level of organic matter in the soil to between 5 and 8 percent and that takes a fairly large amount of organic matter. A few years back Keith Baldwin, a professor of soil science at North Carolina State University, wrote an article about improving clay soils for Taunton Presses Kitchen Garden magazine. While he used a non renewable product the basic concept is the same, add lots of organic matter.

Here is a link that might be useful: Improving clay soils

    Bookmark   May 1, 2011 at 6:55AM
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Thank Kimmer, I have read that article - it is a good one. He tilled the organic matter into the clay whereas I just laid it one top because I was strongly cautioned not to till clay. Well, I went to our local Grange today and was told, "No, I have not missed the planting season provided I provide overhead irrigation for the cover crop." So I have decided to till in a soil building compost, alfalfa pellets and composted manure. Then plant a cover crop mixture of vetch, rye and legumes.

I also thought about Diakon radishes, Marigolds or Alfalfa as their roots extend deep into the soil. Which do you think would be best and why?

Nice, colorful photos Jon. Maybe see you in the community sometime.

    Bookmark   May 1, 2011 at 7:44PM
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You can till clay, if you do it at the right time. Tilling too wet clay makes for major problems and trying to till too dry clay is about immpossible. Then, once the clay has enough organic matter in it it probably would not need to be tilled again unless someone walked on it or other wise compacted it. These simple soil tests may be of some help.
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 your 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.

    Bookmark   May 2, 2011 at 7:06AM
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Your cover crop sounds good for Spring & Summer.
For late Fall & Winter you may have luck with Rape, it is a turnip or close to the turnip, in the same family.
Rape is said to help break up clay soil & you can spread compost in the Spring & turn it all under.
I am not sure why some one would tell you not to till.
Yes it can be messes, but breaking up the hard soil is the best way to get Organic Matter into the surface.

    Bookmark   May 3, 2011 at 9:14PM
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Try cereal rye in the fall with purple vetch. Grows all winter, extensive root system for organic matter (no tilling) and lots of mulch/compost, plus it is pretty to look at. I've done this and it works.

    Bookmark   May 5, 2011 at 9:15PM
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All this has been good, thank you. Yet, I went to a Master Gardener's plant sale today and told them of my plans. While they all seemed to think it was a good plan in theory, they also seemed to think I was wasting time and money. Suggesting I just lay down tons of organic matter and plant into it.

To amend with cover crop or not is the question. I want to improve the soil before planting shrubs, conifers, trees and perennials. I've already done some lasagna gardening and still no worms although soil test indicates clay-loam now and not just clay. It also indicated a very low volatile organic content and other nutrients like Nitrogen. A drainage test indicated it does percolate although moss is growing which would indicate poor drainage.

What say you? Till in manure and compost then plant a cover crop beforehand or just load organic matter on top?

    Bookmark   May 7, 2011 at 8:07PM
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From clay to clay-loam, I say you have won the battle, if not the war. Do what you like, if it works great, if not, you have learned from the greatest school on earth-Experience.

Here is a link that might be useful: My way to get nutrients

    Bookmark   May 7, 2011 at 10:01PM
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I agree with the MGers, Get a hold of some killer compost and plant in it.... If you keep it moist it will provide you with awesome plants.

But I would add about 4" of Compost and 2" of shredded leaves on top of that, if you keep it moist ,you will have so many worms, you will start to get squeamish ;-)

    Bookmark   May 7, 2011 at 11:36PM
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A little late, since it is July, but I recently moved to Medford and asked the state extension about cover crops for help choking out weeds, and to prepare for later planting of fruit trees. I was told buckwheat was fine, but it needed to be planted in spring for a summer crop. In early fall I could plant annual rye grass or clover. They same cover crops might help you.

    Bookmark   July 16, 2011 at 4:15PM
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Buckwheat is a fairly short season crop and I have planted it two or three times over the summer and had each sowing grow to blossom stage. There is still time to grow Buckwheat before frosts even here, and maybe two more since the first frost is usually not the end of the growing season.
I usually don't seed the Field Rye until late September to mid October.

    Bookmark   July 17, 2011 at 6:11AM
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