I bought a former rental house, and the backyard was neglected for years. There’s a ‘lawn’, and a bunch of trees that are a mess. Before I try and redo everything, I’m stuck with the problem of the native soil.
From the top on down several feet, at least, the ground is silty clay. Not a pebble or grain of sand in it. When it rains it doesn’t drain, and unless you’re stepping where the lawn is you sink into it and it sticks to your feet. Tree roots from all the trees are all along the surface or just below it, and they’re everywhere. I’m finding roots 20 feet from trees just under the surface.
I need to regrade the yard and add drains to get the water out of the yard, but I have no idea what is the best way to deal with all this clay. A landscaper who removed some bad concrete mentioned he could shave off several inches of dirt, stripping away a layer of clay and the roots, and I could then add better soil and mix it in to get something better than what’s there.
If I strip off several inches of clay and add soil, will I just end up floating off the top soil layer? Will mixing in new soil with make a whole lot of difference? I’ll still have a clay layer several inches below at least, so will tree roots still want to skim across the surface? Will it still be a potential bad ponding issue?
Tried the internet, but everything was focused on garden planting beds, not the entire yard. What’s my best option here?
The trees are going to go next year, so I’m not worried about them. They’re along a fenceline which will preserve most of their roots so they don’t fall down until I get to them for good.
My plan, if I proceed with removal of the upper few inches, was to add sand/organics/no idea what’s best, rototill the whole mess in, and hopefully have 6-8 inch depth of something approaching normal soil. Before spending a bunch of money in that direction, I’d like to know what the best thing to do is.
This article gives good advice. What works for a garden bed will work for a new lawn.
It mentions adding amendments, organic compost, sand, gypsum.
I’d be inclined to buy earthworms and introduce into the soil. Make sure there’s plenty of composted material for them to eat. This would be the last step, AFTER tilling. Gently rake them in.
There’s different Worms for different jobs. I know from personal experience that worms are very effective in improving soil. They are cheap and worth trying. Imho
Choose Super Reds for Lawn Aeration, In-Garden Aeration and Composting, Outdoor Composting and Fishing
Super Red European Night Crawlers belong outside. They are treasured for their power to aerate and fertilize lawns and gardens. Some people elect to use Super Reds for outdoor composting because they can survive temperature extremes better than Red Wigglers.
Super Reds are the big brother to our Red Wigglers. They grow 4-5 inches long and are very active. They will work on compost, but their claim to fame is all those wonderful tunnels they make. They will burrow through many feet of soil, and these tunnels aerate your lawn and garden. They also generate and distribute their own natural fertilizer.
So, this was discussed on a fruit-growers mailing list I’m on a few years ago, in the context of someone wanting to grow raspberries on heavy clay. The consensus was that adding a lot of organic matter (either rototilled in, or on top) was better than adding sand, because there’s a risk that if you add stand you will create concrete.
One guy rototilled a 3’x30’ area, adding 4-8 cubic feet of peet moss and half a yard of prepared compost mix.
Another guy covered his clay with “a layer of leaves and grass clippings, covered with 4” or so of wood chips". He also recommended adding some gypsum to improve the tilth if the soil. “Get the biology going and let it do the heavy lifting”.
I do organic lawn care/soil care. My take: Adding sand is largely worthless. To make compacted clay soil usable, add organic matter and lots of it. Adding a very healthy dose of gypsum will also loosen it up (you could do 40-50#/1000sf).
But organic matter, by way of top-dressing with compost, will do wonders. And gypsum. Just don’t do sand.
(Adding big rock matter (sand) to very small rock matter (clay) doesn’t give you medium-sized rock matter (silt)).
Compost. Compost, compost, compost. (Not made from sewage sludge, which may contain heavy metals and/or pharmaceuticals.)
No sense adding worms until there’s something there for them to eat. And if you are adding earthworms, make sure you’re adding the right ones for your area. If you’re in the USA, check with your county Extension office.
Use finished compost, not the hot stuff, if you want to seed right away or soon. Compost that’s still working may kill the seed.
If you till, make sure the soil’s dry enough. Tilling clay when it’s wet is a bad idea.
ETA: get a soil test. You may, or may not, need lime or other amendments; but adding it if you don’t need it is also a bad idea.
I wasn’t sure about the sand either. That article mentions it, but I haven’t tried sand before.
I love the bulk compost available here. It’s similar to the home compost people make. It’s warm too the touch, a big pile puts off noticable heat from the composting. The worms I introduced seemed to like it. I tried giving them plenty to eat with the other amendments.
I didn’t use seed. I bought sod. Put it down myself.
So out of curiosity, if I go about adding all that stuff to the soil and till it in, do I co compacting it to a workable level, or leave it fluffy? If I leave it fluffy the yard won’t drain.
If you compact a heavy clay soil, it certainly won’t drain. Compacted clay is hardpan, and pretty close to a clay pot: it impedes both water flow and root growth. Fluffy soils do drain, they’ve got air spaces in them which allow water to flow through when it’s wet.
The sod probably does need to be tamped down, to some extent, so the roots make good contact with the soil below. Not more than that.
I’m not sure what tool one uses on a lawn-sized scale, but using something to rip holes through what’s probably some existing hardpan is a good idea. On acreage you’d use a chisel plow, or maybe a spader if the hardpan’s near the surface. Maybe just some sort of lawn aerator tool would work on a lawn; though I don’t know whether they go deep enough. Roots will work their way through hardpan with time, but some plants are much better at it than others. I don’t know about lawn grass. Again, if you’re in the USA talk to your county cooperative extension office about what they’d recommend.
Where I live the soil is basically clay and I bought the house new. The backyard came graded with sand with St Augustine sod installed over it. The St Augustine grows well like this.
The first step I did was to install heavy duty drains - not the cheap black flexible pipes but 4 inch PVC pipes with holes bored in it (available at Home Depot)
Next I like growing fruits and fragrant plants. So trees that can withstand the climate (zone 9) went on raised beds (beds raised at least a foot above the ground). I used potting soil and then mulched them over. Trees that cannot withstand the climate (Tropical trees) went in large whiskey barrel pots that can moved to the garage over winter.
It really depends on what you want to grow. If it is just grass, then level and grade with sand - install good drainage system, put down the sod and you are all set.
If you want to grow trees/plants : either buy plants that can withstand occasional water pooling at their roots or use raised beds.
