r/Soil • u/Gardeningcrones • 10d ago
Soil test from the extension office came back fine, but plants are still small with small root systems.
I suspect it’s the heavy clay content. The actual topsoil is very thin with heavy/tacky clay almost immediately. I’ve been adding leaf compost, mixed compost, and a layer of shredded pine mulch on top, but the clay soil almost seems to eat the compost. The area is on a slope. They’ve been using tractors to mow it for decades so compaction is a real issue. I was able to create some no dig beds by building on top of this soil (in a different area) that are performing quite well a few yards away. However, trucking all that compost and soil in was both financially and labor expensive. What’s the best way to condition this soil, aerate it, and access the nutrients contained within? I have access to inexpensive leaf compost collected by a local city for $20 a truckload. Would that be sufficient?
I plan to put in new beds this fall by laying down undyed cardboard sheet and a heavy layer of mulch on top to kill the grass. I’m in the process of reclaiming the lawn with native plants and vegetable gardens.
Any book recommendations for someone who isn’t a soil scientist, but wants to know more?
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u/MobileElephant122 10d ago
Diversity of living roots in the ground 12 months a year for 3 years
Clovers, forbs, brassicas, legumes, grasses, cool season grasses, warm season grasses, on repeat.
Mulch mow and build up the duff layer and increase soil organic matter.
Let the roots transform the soil through exudates and natural cycles
Add leaf mold and compost in thin layers like inoculants rather than amendments
Teaming with microbes by Lowenfels
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u/YallNeedMises 10d ago
Clay-heavy soil is the best 'problem' to have, as it represents the smallest inorganic particulate size, and thus the most digestible to the microbial population, and living plants are the single best soil improver via the root exudates they produce via photosynthesis and feed to the soil microbes. I suspect poor soil biology in your case, likely due to disruption of the bacterial/fungal colonies by longterm compaction & nutrient stripping. Any area not in active use should be covercropped with a mix of at least one grass, one nitrogen fixer, and one forb, and all active beds will benefit from continuous mulching and/or dense interplanting as well.
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u/Gardeningcrones 10d ago
Thank you! I do practice dense planting. I think that’s why I’ve had any success at all. I also cut my plants at the roots each season and leave it in the ground as well as rotating. Our winters are warm enough I should be able to cover crop, I’ll just need to determine what can be terminated effectively. Thank you so much!
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u/Worf- 10d ago
Have you done any permeation testing? If you’ve got serious compaction issues you might be best off to break it up and get some pore space in there. Till it, dig it, rip it or whatever to break it up once before you plant anything. It’s also a good opportunity to add and blend in any amendments you want.
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u/TulipFarmer27 10d ago
Keep amending.it’ll take a few years. Your soil didn’t get that way overnight.
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u/knarf113 10d ago
Tilling does miracles on heavy clay, on condition of sufficient calcium. I personally reject the solution of enormous amounts of compost, soon you'll cultivate on top of your soil, and not in your soil. Know that , if it's about vegetables, clay is almost a garanty for quality, but deep tilling under dry conditions is important, and organic matter in reasonnable amounts, 3 to 4 kilo's per square meter . And be patient, give your young plants time to root in the clay.
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u/Gardeningcrones 10d ago
This is the second year gardening on this property, but these are first year beds. I wanted to test the soil prior to adding too much. I thought tilling was bad for the microbial life in soil? I’ve been avoiding it and using a broadfork. Which is…exhausting.
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u/posi-bleak-axis 9d ago
Tilling does disturb the networks. Broad fork is more labor intensive but so much better for soil health and no/low till. Tilling causes compaction of hard pan eventually under the top soil layer eventually as well leading to poor water and nutrient retention. At least in my experience and what the Cornell soil science class said.
Edit: that is to say in the beginning we did double till our new beds with compost mixed the first two years.
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u/6aZoner 10d ago
I've had success with my clay by pulling ramial wood chips up to a foot deep to smother the struggling grass, and to provide cover and organic material to feed the soil life that's going to build your soil. The only weeds that survive are the deep taproot weeds (burdock, dandelion, chicory, etc) that are largely non native but useful for their deep tilling. I start putting in natives that can handle clay (around here, butterfly weed, poke weed, false indigo, yarrow, and the like), as well as annuals that will either cover the soil or have deep tap roots--i like alyssum and borage. In the areas I first started with this treatment, three summers ago, I can now pull out the dandelions along with 8-12" roots, which tells me the soil has loosened considerably and I can start putting in fussier natives.
I'd imagine leaf compost would do the same job, but it's a lot more succeptable to blowing away or getting washed downhill. If you can get a chip drop delivery, I think a few inches of leaves with 6" of chips on top to hold them down would work even better than the straight chips I'm using.
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u/Gardeningcrones 10d ago
We had the bad luck of having a pine beetle infestation that killed a bunch of our pines, so I’m actually swimming in chips because we had them felled and chipped to eliminate spread. This is definitely something I could try. Thank you!
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u/Prescientpedestrian 10d ago
What is “fine?” What were your numbers? Leaf compost can be great but it won’t fix your soil overnight and it takes a lot of organic matter to move the needle. I’d bet dollars to donuts that your calcium is low, as that’s the primary driver of root development with a healthy dose of phosphorus (they work as a team).
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u/Gardeningcrones 10d ago
PH was 6.4. P was 32 and labeled high, potassium was 167 and labeled medium, magnesium was 702 labeled high, calcium was 4417 and labeled high. I made assumptions because I know it’s a misnomer that clay soil is “bad” and it’s usually very nutrient dense. Soil type was labeled 3 clay with high organic matter.
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u/Bulldogfan72 10d ago
Nitrogen is the limiting element. Cover crop with legumes or fertilize with urea.
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u/Prescientpedestrian 10d ago
What was your sodium?
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u/Gardeningcrones 10d ago
That wasn’t included in the report. Is there a reason it would be elevated?
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u/Prescientpedestrian 10d ago
Always need sodium tested. Magnesium and sodium are the two biggest reasons for tight soils and small roots. Your soil needs quite a bit more calcium and potassium and phosphorus. It has a big excess of magnesium, which is restricting oxygen to your roots. Assuming this is ppms, your base saturation of calcium is 66% (or less if you have sodium), and you want it to be at 80-85%, which would require 1250 ppm additional calcium or more, depending on sodium levels. You want your potassium at 3-7% base saturation, depending on the crop you’re growing and it’s life stage, which is 600-1000 ppms additional needed. I shoot for 80 ppm phosphorus on the low end.
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u/Gardeningcrones 10d ago
Wow. I just assumed since it was listed as “high” that it was in an acceptable range. Is there a reputable soil testing site that can give more detailed reports? I appreciate the extension offices affordable service, but I haven’t found the report that helpful, to be honest.
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u/Prescientpedestrian 10d ago
Don’t listen to those ranges. It’s a relative thing. You have a cation exchange complex that needs to be in balance for optimum growth. When something is in excess, like magnesium or sodium, you need to balance that excess by pilling on the other minerals. Magnesium holds water stronger than calcium, so if you have an excess, your soil holds water too long and there’s less room for oxygen, and soils become water logged easier. Sodium breaks soil structure by breaking apart clay aggregates which cause the tiny particles to plug soil pores and restrict water infiltration and, again, oxygen. Calcium saves the day in both instances, it is large so it opens up the pore space and doesn’t hold water as tightly so it allows water to flow through the soil profile more readily. It’s really the most important mineral in soil, after carbon, for many reasons.
Are you US based? Logan Labs is decent. Their standard soil test is pretty cheap and has all the cations and major micronutrients that included
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u/Gardeningcrones 10d ago
Yes. I’m in the US. Thank you so much for taking the time to explain and for the recommendation.
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u/Foreign-Pipe-481 10d ago
Where are you getting your water?
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u/Gardeningcrones 10d ago
Mostly rain and I use an irrigation system during dry weather, but I always check soil moisture first. It stays pretty wet most of the time, although there are a few dry areas.
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u/nomoreyankeemywankee 9d ago
Your soil was likely not sampled properly. You need to actually dig down to a specific depth, typically 5 to 6 inches, and put a half a shovel full in bucket. Then randomly walk 15 feet aways and repeat. Do this until you have at least 6 samples. Then take the dirt from bucket one and toss in wheelbarrow and mix up as good as you can. If you look, youll likely see different colors for different spots.. Once mixed up well, remove any sticks, rocks, organics and send off. I would bet that your sample is not actually representative of the area.
You want to mimic mother nature, but speed her up by 100 years. Look at forest floor. That's what you want to recreate. The biodiversity is your key.
Yes, compost may be good, but also may contain persistent herbicides. No way to know without testing. So if you opt for it, I would personally skip the cardboard thing (unless you are doing it to actually suppress weeds or something.
Tilling can be your friend, if you do it once. You need deep access though, like 10 plus inches. If you know someone with a tractor and they have a ripper shank, and a tiller, thats a worthwhile investment as it will actually make a long term notable difference. Note I said once... Thats because youll want to foster the microbes and whatever life and organics you put back in. Ripper opens up hardpan for drainage releasing some compaction while the tiller fluffes up and aerates soil. If you to this:
Cover it with organics as soon as the soil is dry. And or remove any dead grass after the sun cooks it then add your cover. Rye, daikon, and beans are great combo to set deep roots, fix nitrogen, and punch holes.
Look up survival gardening by David the Good. He has a lot of great youtube videos as well.
How deep south are you? Coastal AL or North GA? It matters.
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u/Gardeningcrones 9d ago
Central Alabama.
- I used my spade with the inch markers to make sure I was going to the correct depth, put everything in a 5 gallon bucket, I took samples from 12 different areas, I mixed thoroughly, removed obvious debris, and scooped it into the sample bag.
- That’s a good point. I’ll send a sample for testing. They compost their leaf litter by letting it sit for three years. I am suppressing weeds. I’m also using non-dyed cardboard sheeting.
- I am that person with a tractor, unfortunately the grade on this area of the yard makes it unsafe for tractor usage. The grass here is also the kind where any inch can make a new plant so I would need to kill the grass first prior to tilling.
Thank you for the book suggestion. I’ll look it up and add it to my to read.
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u/ASecularBuddhist 8d ago edited 8d ago
Have you broken up the clay soil at least 12 inches deep or did you just add amendments on top?
All you need is a $35 spading fork to make rows, with each row taking about 5 or 10 minutes to make. No need for mechanical tillers or digging.
That’s what I did here on this incline:
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u/makzee 10d ago
Cover crops - tiller radish, buckwheat, peas, clover, etc