breaking up the subsoil is an act that ask for a really good reason,and one should look for the alternatives before even thinking about doing such thing.

Do some research on cover crops or green manures. Your local extension service should have bulletins appropriate to your locale. That should provide the info on when to plant for your area and how to incorporate these forbs for optimum effect. I would avoid using the comfrey as cover crop myself - this plant is very persistant, reseeds too freely, sprouts back from the roots and is pretty much impossible to remove thoroughly.

Repeated plowing or tilling often exacerbates the compaction, so I'd avoid doing much more of that. Any plant roots that penetrate deeply will help to break up compacted soils and 12" isn't all that deep......I'd expect to see gradual improvement from just the routine growing and harvesting of crops.

And FWIW, I'm not sure I'd agree with the previous post. Unless there are other issues not disclosed, loosening or breaking up compacted subsoils is not necessarily a bad thing and often desirable.

Thanks, gardengal. I agree that breaking up compacted soil can be helpful, both to make it easier for roots to penetrate the soil (and bring up nutrients) and for drainage. I'll certainly scratch comfrey off the list if it comes back from the roots!

JPW, many garden vegetables can put down roots several feet -- here is a classic study. Johnny's describes alfalfa's taproot.

There have been a few threads touching on this subject, but they seem to contain contradictory information on what crops work best for this purpose, how long they need to be left in, etc. This study contains some of this information, but has gaps.

Has anyone tried to use deep-rooted crops for this purpose?

How long it might take will depend on many things. I broke up the hardpan my sand had with just two years of green manure crops and adding other types of organic matter. It may take longer in clay, or it may not.

The question is not how, but why. After re-reading nygardener's post, i cant help but felt you're going the hard(and in this case wrong) way of gardening. Why dig down when you can build up with less effort? There is almost nothing that you cannot plant,as a regular vege gardener, without actually having to even see the face of subsoil , provided you taken good care of your topsoil. Yes, almost everything good happen at topsoil level for common vege gardener.

If you're into trees, than more the reason to not worry about the subsoil. Trees are strong with roots. So just prepare your topsoil nicely, make raised beds if necessary, and leave the (often)nutrient depleted subsoil alone. Go up instead of down is the better way to go.

Ceth K and I are thinking along the same lines... why? It seems like hard work for not much gain.

I didn't say that alfalfa roots don't go deep, I just said I don't consider them "taps".

Hard work?? How so when the plants (i.e. cover crops or green manures) - not the gardener - are expending all the effort? btw, alfalfa IS considered to be a tap rooted plant, with a major, deeply penetrating root and smaller laterals where the nitrogen fixing nodules develop. Since alfalfa roots have the ability to grow as deeply as 25' (they have been measured as deep as 60'), this is an often recommended solution for compacted soils.

We plant Innoculated Chrimson Clover seeds in August to Spetember. They are great for clay tough grow in cool weather and add nitrogen to the soil. Great roots and break up the hardest clay. Also for clay, gypsum (sheetrock) broken up with lime realy helps losening up the soil. Lots of leaves are great till in late spring just prior to planting. Oh with clay lime twice a year. Most clays have a very low ph but loaded with nutrients. Lime helps free up the chemistry of the soil making the nutrients more avalible and of course making the soil loose.

..
I just read we have 20 feet of topsoil in this area which is one reason why it's big on orchards (citrus & avocado).

I have hard pan and like'd to break that down so the winter rains retain more of the water. We get little rain outside of the winter season and it tends to overwhelm the watershed with all the streets and development.

What can I do to break up this hard pan and bring a greater capacity to retain water on my little tract home piece of property?
..

There is no particular relationship between clay soils and low pH - clay can have any pH, depending on the base materials comprising that clay. It will vary widely according to region. Gypsum is highly overrated as a soil conditioner. It's primary value is to sodic soils - it is rather more of a wasted effort in other soil types. And lime does nothing to loosen soil.

The tried and true method for loosening clay soils is with the addition of organic matter, either through the use of compost and other organic mulches or the planting of deep rooted cover crops or preferrably both. It is not an overnight fix.....improving soils is a longterm process.

rott, have you considered a rain garden? A rain garden is one that is designed to limit runoff and utilizes plants, often natives, that will help to filter pollutants as well as improve soil conditions through their growth habit and root structure. Just like any other type of garden design, they can be extremely attractive if well-conceived plus they are ecologically sound and feature a degree of sustainability that is typically missing in other types of ornamental plantings. If you wish to grow edible crops, these may be best addressed via raised beds (filled with imported soils) - while not the same concept behind a rain garden, raised beds will also have the capacity to absorb and retain moisture and limit runoff.

Getting back to the original poster....Perhaps you would want to deep-root a portion of your soil at a time.
Daikon radishes and similar radishes can be planted in early spring and likely finished off in mid-summer where you could plant a late crop.

Alfalfa and yellow sweet clover need to be spring planted...best with an oats nurse crop. The legumes then might need to live for much of the second year for best root work.

Thanks, Wayne! Yes, I'm planning to work on a couple of beds at a time, as part of a rotation. What kind of alfalfa do you recommend? How often should I mow the alfalfa/clover/oats beds during the year and a half from initial planting to finally turning them under? Should I plant all three together, or alfalfa/oats in some and clover/oats in others? Does winter rye have any value as part of the combination? These gardens are in zone 5, maybe 4b (the western Catskills), in full sun.

Sorry, for the the copy paste here is a link about lime studies there are many more just google if you want. http://www.ipni.net/ppiweb/ppinews.nsf/$webcontents/8D4983658FA1282785256962005E31DE/$file/96195-CSS+Ryegrass.pdf

I cant find the studies I have read about gypsum. But I will tell you it does make a diffrence in how hard the soil is compacted. My soil was so hard that after discing i had to have a farm tractor come in and break up the clay more. I have a commercial tiller that would not even start on it. After 3 years of gypsum and lime I can now shuvle or till with my tiller. In another year or so I hope that it continues to work. You should always consult with your local agg ext office. They where the ones that reffered me to my regiment.

ps I had been working the soil for 2 years prior with just leaves with almost no results.

..
gardengal48,

Thanks for the reply. I donâÂÂt have the resources to invest in a rain garden right now. All but one of our downspouts empties on to our property either directly or across the driveway and then onto the grass. IâÂÂll divert the last one from the street before the season starts in earnest.

The lawn out front slopes away from the house and IâÂÂve noticed when IâÂÂve left a sprinkler on too long during my weekend deep watering routines it will leak through crack in the pavement to the street and quite some distance from the sprinkler.

We have a winter rainy season and remain pretty dry the rest of the year. So we get a lot of rain during one season and our soil out front just isnâÂÂt holding it in.

I planted a couple of trees out front and I think thatâÂÂs starting to do the trick on one side. The other side has an old tree right smack in the middle.

IâÂÂve been propagating California poppies from an 89 cent pack of seeds I bought as an impulse buy in a drug store some time ago. I threw some seeds around when we first moved in and from the couple that thrived we now have them spreading about as I harvested the seeds over time. I go around and trim them in an attempt to keep them going all year long so their taproots keep running deeper and become more substantial. Time to spread a bunch of the seeds I saved now that itâÂÂs the end of November.

One of these days IâÂÂll find some other suitable natives to plant. Native California plants offered are often Northern California and not always suited for our hot dry spot between the desert and the coast.

For gardening IâÂÂm probably going to go down the container path. Our garage is in the back so a lot of ground is taken over by concrete. The rest of the yard was already planned and planted when we moved in and the open grass area is needed for the dogs.

I havenâÂÂt figured out what to do with the lawn out front. IâÂÂm having troubles with the âÂÂwell conceivedâ part. In the meantime I keep the watering to a minimum and alternate between grass cycling and harvesting grass clippings for feedstock in the digesting bins I maintain for our yard clippings and kitchen scraps.

to sense
..

nygardener,

I suggest a couple options. One is planting "summer" alfalfa with oats in the spring. The oats help to prevent weeds while the alfalfa is getting started and the oats straw makes good organic matter. The alfalfa is considered as a one year crop. You can get this from Johnny's.
I wouldn't worry about mowing[mulching] till the next spring.

Fedco sells oats and sweet clover for a one year or 1ý year cycle...mow when the sw clover dies in August or later. Mamoth Red Clover can be treated the same as SW clover.

I think that the fastest answer is daikon forage radishes....spring planted and a second crop planted in late summer.

Rye is a good turf crop but not tap rooted. It is fall planted and a bear to handle in spring. Small areas can be clipped off by hand in spring and then easily killed by tilling.

Sounds like a plan, thanks!

Here is a video about radishes similar to daikons.

Here is a link that might be useful: tillage radishes