Breeding for wet, heavy clay soil

[Cathy A]

Walking in my yard today, I am reminded how tiny my raised beds of excellent soil are, and how much land I have around them that is heavy, dense clay prone to flooding.

Has there been much breeding work on vegetable and fruit varieties that thrive and fruit in heavy, wet clay?

I am thinking of large-seeded vegetables such as most legumes, tomatoes that are started inside in finer soil and transplanted out into the clay, landrace cucumbers, and so forth. This couldn't be no-till, and would be either rototilled every spring before planting, or hoed.

I could much more easily grow a large number of plants if I could use the clay with minimal improvements beyond hoeing or tilling. This would especially useful for landraces or other outbreeding species.

[Adrian]

We have clay soil!
Our method we cover the seeds of compost or we mixed c compost at clay.
Plants are more strong in compost  than in potting soil.
Our alone problem is the eggsplants but for squashs, tomatos, melons its perfect.
We have a lot of spontaneus plants who germinate at placements or we expand compost on our clay soil
For example we can see here spontaneus watermelons and tomatos in this picture.

[Cathy A]

If I have to buy a significant amount of compost, unfortunately that would defeat the purpose. The amount of compost I currently make at home all goes into the raised beds of excellent soil.

What I'm wondering is whether it would be possible to breed good vegetables to grow in fairly poor clay soil with very minimal soil amendments. Adding large amounts of compost to clay to improve it is well understood, but that's a different thing.

[Adrian]

You don't have required of a lot of compost.Cover the seeds is sufficient!
I think clay soil is the better of the soils and i think it largely possible even without compost.
He keep water so long time that directs seedlings can germinate without problem
I have for example sow beans without compost in clay soil.
The better for me in clay soil is squash, bean peas, chards
Squash in direct seedling is for me efficient.
Chards have very big leafs.
Squashs are more vigorous when i use the drys  peas plants for mulch them.
I have even succesed radish.
Try differents things in direct seedling you will be very surprise of the potential of your soil!
It is very efficient if you don't have slugs.

[William S.]

I have a 7 inch layer of silty clay loam over a 7 inch layer of clay accumulation. What I do is buy and add sand- preferably silty sand. I only rototill sand in to the loam though. If it was only clay I would add the sand as an artificial soil horizon and try hard to never ever rototill it in. My family used to make more compost back in the 1990's when I was a teenager. We had bagging mowers then and picked up other peoples leaves they were throwing away. You just mix dry leaves with fresh grass clippings about 50:50. Now we never have enough! Its mostly just kitchen scrap compost now. I think bought compost is way too expensive. I do buy small amounts of organic fertilizers but it isn't anywhere near the recommended amount. I also use my wood ashes on the gardens as we partly heat with wood and pellets.

Also another trick. I've been growing fava beans in sawdust. I suspect it would work for other legumes as well. It improves soil, in the long run it will decay. In the short run (at least a few years in my dry climate) it works for legumes because they get nitrogen from their symbiotic bacteria in root nodules.

With soil modification it might work well to just modify a little layer on the surface.

I grew up with a clay loam but my parents formed raised beds from the native soil without the boards that are so common today. Just hilling it up did improve drainage.

I suspect some crops and varieties are also better for clay. Try short fat roots like Kral parsnip and oxheart carrot. Then just lots of testing of crops and varieties.

Also Google seems to have a lot to say here is the top link:


https://empressofdirt.net/best-vegetables-clay-soils/

[Cathy A]

Adrian, unfortunately I have a major infestation of slugs and tiny snails. They are concentrated in the wettest areas and places where grass is high, so tilling the clay and leaving some bare earth might be enough to limit them.

I use a combination of beer traps and hand-picking to keep them under control. They haven't been an issue for my core crops, but I've given up on growing blue hubbard squash because they can swarm and eat an entire large fruit overnight.  Breeding a slug-resistant squash would be another interesting project!

William, I've read that adding sand to heavy clay can turn it into something approaching concrete, so I think you are wise not to till it in. The charts I've seen on soil types suggest that loam is a lot of sand and organic material with a very small amount of clay included. If you had sand as the base soil, adding a little clay could be a good thing, but not the other way around.

Soil here is class 6w heavy clay with drainage issues. When digging out grass to renew or extend beds, I can dig out a block of clay the size of my head with grass roots in it, and pick up the entire block by the grass and move it around as one unit.  It's not friable or crumbly at all until a lot of organic material is added.

I agree that bought compost is very expensive. I purchase a few cubic yards when creating new raised beds to get things started quickly, then use my own homemade compost to maintain the beds afterward when much less is needed. Since we heat with wood in winter and routinely burn at least 1 1/2 cords, we have plenty of wood ashes to add to the gardens at the end of winter. However, I have to be careful about unbalancing the pH of the beds, as I've had some problems with potato scab. So a plan is necessary to figure out which beds should let lime and wood ashes, and which should not.

I don't have a good source of sawdust, so I've never pursued that. OTOH, we have enormous amounts of leaves every fall, on the order of 100 large leaf bags. We dump them in our woods and leave them to rot. When I need mulch, I grab some wet, partially-decomposed leaves from just under the surface of the pile. When I need a little additional compost, I dig deep in the leaf pile and use leaf mold from the bottom. It's a pain to remove the roots that develop in it, but it can be done. This pile is over 10 years old and gets another 100+ leaf bags added every year.

[Adrian]

I don't know if your climate is sufficiently sweet  but we sow greens fertilisers the automn in our most bads soils for example mustarde, radish,aragula,mizuna cabbage,phacelia, wheat, some peas, saradella,lupins.They improve the soil structure at  spring for us some can kilk nematodes.
They are all edible.

[Steph S]

Some amazing results on clay soil in Virginia using cover crops and mulch for a couple of years.  And a little bit of compost...
https://www.youtube.com/watch?v=2_B6YEuQQmQ
Adrian's method of using a small layer of compost on the clay sounds pretty awesome too.
Our native clay here has a pH of 4 and will pretty much grow moss and lichens without amendments.  I doubt I could do the same (as in the video) here, even with lots of lime.   In order to increase my growing area, I accept that I have to make more compost (or buy some).   But it's a plus for me, that I'm adding carbon to any soil area I decide to open up and use.  No rewards (yet) for carbon farming but I feel good about the stewardship.  In fact clay soil is said to bind and sequester carbon better than some others, which gives me hope that I'm on a path to neutral while improving my soil and habitat.  I wish carbon sequestration in soil was a simple science but until it all becomes clear, I'll just try and do the 'four per mille' on land I'm using to grow crops.
 I've been lucky to get horse manure at a much lower cost than finished compost products.  It's basically free, but for the good man who loads and brings it to me in his truck, and I pay him for the work.  I still pay the same guy when I buy a scoop of compost somewhere.    The spring manure is a bit fresh not 'finished' but I'm okay with piling it on a tarp and letting it mature for the summer. (I put it under a tarp one year, but that turned into a rat hotel so I'm sticking with on top of the tarp now.).

[William S.]

Cathy, your leaf supply sounds awesome. My family's 90's era hot compost recipe was about half leaves and half fresh grass clippings.

[Jeremy Weiss]

I don't know if your climate is sufficiently sweet  but we sow greens fertilisers the automn in our most bads soils for example mustarde, radish,aragula,mizuna cabbage,phacelia, wheat, some peas, saradella,lupins.They improve the soil structure at  spring for us some can kilk nematodes.
They are all edible.

Mostly a good idea. Though I should point out that several lupins need to be cooked in order to be eaten (depending on which species you go for) and that, if you are in the US, there really isn't a good source for seradella seed (they just don't seem to sell it here, I suppose we have enough ground legumes already.)

[Tim DH]

No one has mentioned the ‘Old School’ method of digging and allowing the frost to break up the clay. I used it last Millennium on a greasy clay. It’s HARD work and the ‘fashion’ (?) for ‘No Dig’ seems to have swept such ideas away.
Leeks have a reputation for helping break up clay.