Soil & Turf · Field Notes
The holes close in about two weeks. It is the only stretch all year when anything you put on the surface has a clear path into the root zone — and most people spend it raking.
You rented the machine, you made your passes, and now the yard is covered in little brown cigars. The standard advice from here is rake, seed, fertilize, done.
That advice isn't wrong. It just skips the one thing aeration is uniquely good for, and the window is already closing.
What you just opened up
For roughly two weeks you have several hundred open channels running three inches straight down. Air gets in. Water gets in. And anything you put on the surface has a route into the soil that it does not have on any other day of the year.
Depth is the whole ballgame with soil amendments, and there is direct evidence for it. The NC State turfgrass group compared three delivery routes for the same humate material. Incorporated ten centimetres into the soil: rooting increased. Applied to the surface before sodding: rooting increased. Sprayed on the leaf and left on top: “did not consistently improve rooting.”
Two routes got it into the soil. Those were the two that worked.
Their trial used tillage and pre-plant incorporation rather than aeration holes, so applying it to your open cores is a reasonable inference, not a tested one. But the principle holds: a soil amendment has to reach the soil.
Humic+ Soil Conditioner Concentrate — $17.99 · 32 oz
Humic acid, sea kelp and fulvic acid. One ounce per 1,000 sq ft, straight into the holes while they are open. Read the rest of this first if you want the caveats — they are all below.
Get It Down This WeekFree shipping, no minimumShips from our farmMade with OMRI listed ingredients
Prefer to order on Amazon? Same jug, listed here.What aeration fixes — and what it doesn't
Aeration relieves compaction. It does it mechanically, by physically removing soil, and nothing in a jug does that job.
Worth being blunt about, because plenty of products imply otherwise. A two-year Iowa State trial ran a traffic simulator over Kentucky bluegrass — twenty-five traffic events a year — and found humic substances added to fertilizer did not improve traffic tolerance. No effect on surface hardness. No effect on shear strength. If your ground is packed, aerate. That is the fix, and you have already done it.
What aeration doesn't do is give the soil anything. It opens the door. It doesn't put anything through it.
The lawns that hold up in July are the ones with roots deep enough to live below the top few inches. Autumn is when that gets built — top growth slows, the soil is still warm, and the plant puts its energy underground. What you do in September and October is a deposit on next August.
What the research actually supports
Root mass is the most replicated effect in the humic acid literature. Worth knowing the real numbers rather than the label copy.
Root mass increase in Kentucky bluegrass from humic acid during establishment. The same trial found no change in tiller density or visual quality — the roots moved, the look of the grass didn't. Ervin, Zhang & Roberts (2008) · Acta Horticulturae 783:317–322
Average root dry weight across a meta-analysis of 81 studies and more than 700 data points. Rose et al. (2014) · Advances in Agronomy 124:37–89
Nitrogen use efficiency across 120 field trials, with nitrogen uptake up 17% — the grass got more out of the fertilizer already going down. Ma, Cheng & Zhang (2024) · Agronomy 14(12):2763
The effect is conditional in a way that matters for a home lawn. Across the literature, humic substances do the most in soils low in organic matter and on plants under stress. The NC State summary notes the benefit is “less evident on a putting green containing significant organic matter.”
Which is a fair test you can run in your own hand. If the cores you just pulled are pale, packed and thin on roots, that is the case with the most room to move. If they come up dark and crumbling and full of root, expect less, and spend the money on seed instead.
Read this part
What it won't do
It will not decompact your soil. That is what the aerator was for. The Iowa State traffic work found no improvement in surface hardness or wear tolerance from humic substances.
It will not hold water for you. A Utah State study found humic acid actually decreased soil volumetric water content on putting greens and required more frequent watering, not less.
It will not replace your fertilizer. In two-year field trials, nitrogen rate remained the primary determinant of turf quality. Humic added to a program helped; humic alone performed barely better than doing nothing.
It will not control a lawn disease. There is no peer-reviewed field trial showing sea kelp controls dollar spot, brown patch or anything else on turf. We looked.
And it will not do anything in two weeks. Half the studies in the largest meta-analysis showed growth responses under 5%. The averages are carried by a minority of strong responders — poor soil, under stress, over a full season.
This is a soil tool on a soil timeline. If you want colour by next weekend, that is nitrogen's job, not ours.
The order we'd run it
Four things, in this order, ideally inside a week of pulling the cores.
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Aerate — and then leave the cores alone
Don't rake them off. They look like a mess for a fortnight and then they are gone, broken down and washed back into the holes they came out of. Raking them up means hauling away the only free topdressing your lawn produces all year.
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Overseed, if you're overseeding
Now is when it works. Seed dropped on an aerated lawn falls into open holes instead of perching on thatch, which is most of the reason autumn seeding takes and spring seeding sulks.
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Fertilize on the schedule you already run
Nothing changes here. Nitrogen is still what grows grass and it is still doing the heavy lifting. We are not asking you to swap anything out.
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Soil conditioner last, over the top, then water it in
One ounce per 1,000 sq ft while the holes are still open, then irrigate or let the rain take it down. Watering in is the part that matters — left sitting on the leaf it is the delivery route the NC State work found didn't consistently do anything.
One pass, any tank sprayer, backpack or hose-end unit. Then you are done until spring.
Humic+ is a soil conditioner — humic acid, sea kelp and fulvic acid, made with OMRI listed ingredients. It is not a fertilizer and it is not a replacement for one.
- Size
- 32 fl oz
- Makes
- 32 gallons
- Covers
- 32,000 sq ft
- Cost
- 56¢ / 1,000 sq ft
Why we made one
We farm in Laurel, Delaware — fourth generation on the same ground. Our dirt got tired the way everybody's dirt gets tired, and more fertilizer stopped moving the needle. So we started feeding the soil instead, and after a season the biology came back.
Nobody is more suspicious of a jug of promises than a farmer. That is exactly why we built our own, and why this page tells you what the research doesn't support alongside what it does.
Not by Friday. By harvest.
Humic+ Soil Conditioner Concentrate — $17.99 · 32 oz | $39.99 · 128 oz
Your holes are open for about another twelve days.
Order Before They CloseFree shipping, no minimum32 oz = 32 gallonsCovers up to 32,000 sq ft
Prefer to order on Amazon? Same jug, listed here.Fourth generation · Laurel, Delaware
Sources — Ervin, Zhang & Roberts (2008), Acta Horticulturae 783:317–322 · Rose et al. (2014), Advances in Agronomy 124:37–89 · Ma, Cheng & Zhang (2024), Agronomy 14(12):2763 · Liu & Cooper, NC State turfgrass research summaries (1999–2000) · Van Dyke, Johnson & Grossl (2009), Soil Use and Management 25:225–231 · Lindsey, Thoms & Christians (2021), Agronomy 11(4):611 · Lindsey et al. (2026), Agronomy 16(5):573.