A LOT of clay

[Black_Thumb]

Hi gang. We just moved into a new home in northeastern Tennessee and we have five raised bed garden boxes that came with the house. We have begun getting all the weeds out and have found that the soil consists of a LOT of clay. I have no idea what the previous owners grew in that soil. We want to plant some veggies and make one of the boxes an herb garden. Anyone care to share what I can grow in clay? Also, should I break up the clay as it seems to be very large clumps as well.

 

[Marck]

It is true that compacted or otherwise mismanaged clay soils can have drainage issues, but clay soil also has its benefits such as being nutrient rich, moisture retentive, and less likely to suffer soil pests such as nematodes.

The way to manage clay is to regularly amend and mulch with compost and other organic matter.

For in-ground planting, also consider planting on mounds and avoiding compaction by sticking to paths and stepping stones except when absolutely necessary.

 

[Black_Thumb]

Here are a couple photos of the soil in one of my raised beds. I turned the soil today and took out the rest of the weeds. There are tons of earth worms, grub worms, and centipedes in the soil. Also, since it's a lot of clay, I have large clumps of tightly compacted clay all throughout. Do I need to break thise all up or what?

I'm going to have to buy something to amend the soil with, I think. Any recommendations on what I should buy?

 

[Marck]

It is hard to fully judge by photos, but the clay-based soil in your beds doesn't look particularly compacted. All the same, do add generous amounts of organic matter when planting. However, don't amend to the point hat the mineral component of the soil becomes negligible. Home-made compost or bagged or bulk soil amendments can all work fine. Many such commercial amendments are made from a combination of manure and finely milled forestry wood product, though other sources of organic matter can work just as well.

 

[Oliver Buckle]

My soil is clay and as I work I pull out those solid lumps, let them dry off under shelter, and throw them in the incinerator when I have a fire. They need to get fairly hot , so not huge pieces, and the incinerator has good air flow and burns hotter that a simple bonfire, but it turns them into terracotta. A lot of it breaks up naturally, I thump the larger lumps with a club hammer, mixed with the ash it is a really good additive that loosens up the clay.
Like Marck says, anything organic will help, but the other thing I add is sharp sand. If you buy it as horticultural sand it is dear, as sharp sand sold for building work it is a fraction of the price, but can have salts in it depending where it is mined. I cut the top off the bags and let them fill with rainwater, then make holes in the bottom to drain them. I try to keep three or four bags going so they get more than one lot of rain through them and just add a bit every time I do something.
If you can leave a bit of land for a while rough digging and leaving the lumps to weather can improve the friability considerably, best done in Autumn, freezing seems to help.

 

[Black_Thumb]

It is hard to fully judge by photos, but the clay-based soil in your beds doesn't look particularly compacted. All the same, do add generous amounts of organic matter when planting. However, don't amend to the point hat the mineral component of the soil becomes negligible. Home-made compost or bagged or bulk soil amendments can all work fine. Many such commercial amendments are made from a combination of manure and finely milled forestry wood product, though other sources of organic matter can work just as well.

It doesn't look too bad now because I spent hours breaking up the large clay clumps by hand or with my little shovel. The stuff is super compacted and so it takes quite some time to make the big pieces into small pieces. I'll have to buy something as I don't have any kind of compost pile yet.

 

[Oliver Buckle]

Having a compost pile is great, but you can get away with adding stuff uncomposted so long as you don't overdo it. I cut a fairly large mixed hedge then ran the rotary mower over the cuttings to pick them up. I chucked it all on a fairly raw bed last autumn and dug it over rough, it is pretty well combined now and with a bit of extra added I am intending to plant tomatoes this summer. I don't suppose they will be great, but every time the land gets used it improves.

 

[Herbie]

Blackthumb , you mention that you have tons of earthworms in your soil. Spreading a good thick ( 10cm or so ) layer of well rotted organic matter on top will encourage the resident earthworms to come up and start pulling the top layer down . All their workings will aerate and loosen the soil. It won’t happen over night , but over a season it’s amazing the difference it makes.

 

[Ruderunner]

Earthworms are somewhat scarce in my garden. I've thought about buying bait worms and adding them after a rainfall.

 

[Oliver Buckle]

Earthworms are somewhat scarce in my garden. I've thought about buying bait worms and adding them after a rainfall.

I don't know what sort of worms bait worms would be, nothing like encouraging the natural population though. Herbie's suggestion of mulching is a good one, it is amazing how quickly things reproduce when you get the conditions right for them.

 

[smitty55]

Gypsum is touted as being great for breaking up clay soils without changing the ph. I would suggest you do some research as there are different opinions.

https://treehozz.com/what-is-gypsum-for-clay-soil

How to Apply Gypsum to Clay Soil

The application rate of gypsum for clay soil is based on your soil test results. Spread...

homeguides.sfgate.com

 

[Marck]

Earthworms are somewhat scarce in my garden. I've thought about buying bait worms and adding them after a rainfall.

Commercial bait worms are rarely (ever?) earthworms. They are usually red wrigglers (Eisenia foetida) native to Europe. Red Wrigglers can help break down mulched organic matter at the surface faster (for better or worse) but usually do much less for aerating the actual soil.

 

[Neno Baylov]

You can add beef manure, it always helps with clay soil.

 

[Oliver Buckle]

Gypsum is touted as being great for breaking up clay soils without changing the ph. I would suggest you do some research as there are different opinions.

https://treehozz.com/what-is-gypsum-for-clay-soil

How to Apply Gypsum to Clay Soil

The application rate of gypsum for clay soil is based on your soil test results. Spread...

homeguides.sfgate.com

Plasterboard is a good free source of gypsum, builders fill entire skips with it sometimes. Bashing it with a hammer will separate it from the paper either side, or chucking it on the fire, but it might want slaking then.

 

[DirtMechanic]

Earthworms are somewhat scarce in my garden. I've thought about buying bait worms and adding them after a rainfall.

Don't. That asian jumper worm is still sold as a bait worm. Ravenous, incredibly prolific, they are capable of eating down the compost horizon in a forest and outcompeting natural, slower species.