Compacted clay soil

[carebearmik]

We are trying to finally finish our backyard landscaping on our new construction home. It has been almost a three year process of landscaping construction that has left our soil horribly compacted. When it rains the water doesn't soak in but runs off. An area close to the fence on the south side of my yard is part shade and that area never dries due to my neighbour's yard draining into my swale and combining with my drainage water. It is covered in moss and other weeds that love soggy compacted soil. I dug up part of a flower bed near my shed and I have 2-3 inches of topsoil and then yellow clay miles deep. While digging this bed I did not find one worm or any other bug. My soil has very little organic matter. I want to put in a small area of sod and the rest will be flower beds. I have tried searching online to see what the best way is to deal with my compacted soil but there are a lot of conflicting opinions that have my head spinning. At this time I am trying to locate someone to complete my landscaping so I need to decided what to do. Do I rototill in amendments and loosen my soil? Or do I just touch up the grading with garden mix and over time my soil might improve? I would be grateful for your suggestions or what you did in your gardens.

[PW405]

I would suggest making some of the soil conditioner (Best Lawn Soil Conditioner, or "BLSC") that members of this forum have created. I have clay soil and it has helped water to penetrate much better. There is also another mixture called "Kelp Help" . The mixing process is super simple and you end up with enough to last for quite a few applications. Here's the link: http://aroundtheyard.com/index.php?opti ... Itemid=117

Generally, most members suggest to avoid roto-tilling. It can make seeds from weeds sprout and then you end up with a clumpy lawn.

If the soil truly is compacted physically, generally core aerating is the preferred. Many local landscapers will offer this service for reasonable price. This process pulls tube shaped "cores" out of the lawn so that air and water can penetrate deeper.

I would at least give the BLSC and KH a try. I didn't think it was doing much, but after a good rain, I can really tell a difference in how the soil feels. Seem to notice more earthworm activity too. I've only been using it for a few weeks, but I have been doing a weekly application with a hose-end sprayer (or a pump & tank sprayer) which is 2x the suggested application rate.

[bernstem]

I would recommend a soil structure "jar" test. Instruction can be found here: https://aroundtheyard.com/index.php?opt ... Itemid=117

If you have a clear soil horizon at ~2 inches, it is likely worthwhile to jar test above and below the horizon to see if there is a large difference in the soils.

I would avoid trying to change the soil composition unless you are willing to undertake a massive project in soil amendment. Assuming you have a 80% clay soil and want to reduce that to 40% in the top 6 inches, you will need to remove and replace ~15,000 lbs of soil per thousand square feet. You will also need to blend the new soil mix into the oil soil mix to prevent a soil horizon at 6 inches, and mix it evenly to prevent surface unevenness when it settles. You are most likely better off working with what you have (which is probably not actually a clay soil type).

I'll second PW405's advice. Using the Soil conditioner will help, though it may take several weeks to months to see results. It also won't affect anything else you might want to do with the soil.

Core aeration can help with mechanical compaction, but it will only loosen the soil as deep as the aeration tines go in the soil (usually 3 inches). Considering that, I would combine it with the BLSC if you want to aerate, though the BLSC is very effective and you may not need aeration.

Increasing organic matter is simply the end result of adding organic matter. Mulching leaves and grass will add some, but you really need to add thousands of pounds to make a noticeable difference. Finished compost and Peat Moss are both effective. Peat Moss is higher in end stage organic matter and has essentially zero chance of adding weed seeds, has no nutrient value and is more expensive. Compost has some slight fertilizer value, is higher in water content, can add weed seeds if it is not properly composted, but is much cheaper. I use both. For compost, I spread ~3/4 yard per 1000 square feet. For Peat Moss, I spread 1-2 of the three cubic foot bales per thousand square feet. Compost is generally applied 1-2 times per year. Peat Moss can be added more often (every few weeks if you wanted).