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Organic matter even needed if soil composition is perfect? No worms...

barplants123 barplants123
2 years ago
last modified: 2 years ago

NJ, zone 6-7:

tilled a crabgrass lawn in prep for seeding tall fescue. Soil seemed sandy and light brown, but then I rolled a wet log of it and it proved to be sandy loam mix which happens to be the best for grass. I read clay and silt in the loam is what the roots and fertilizer cling too (and the sand lets water run deep resulting in deep drought resistant Turf Type Tall Fescue roots), so my question is why would I spend the time and money to till in a bunch of compost AKA organic matter ....

Isn't organic matter like %90 just a fertilizer source?

The lawn is going to be regularly fed with organic milorganite fertilizer (or even just synthetic fertilzier for that matter).

BTW I happened to notice a milorganite video mention "in nature, organic material [compost] is only about %5 of the soil" ,and the rest is sand/silt/clay.

I understand good compost has a better nutrient profile than milorganite or synthetics, but compost basically gets eaten up by the plant/lawn AND THEN IT DISAPPEARS. I read many threads on here about how compost disappears, i.e how you shouldn't fill low spots in a lawn with compost because it'll just become unlevel again, and how many add new compost to the garden every year or more.

True, compost would probably hold onto roots and nutrients better than clay and silt in loam, but is compost really necessary in the end?

I have tilled a bunch of loamy yards like this which have light brown soil indicating a low level of organic matter (vs black soil which indicates a high amount of organic matter/compost) and I did not add compost and the lawns come out fine. In fact, it is said that you don't want such dark soil for a lawn, the darkness comes from compost/organic material % of the mix - which is great for shallow-rooting stuff like a vegetable garden to feed and root on plus hold moisture but grass particularly Turf Type Tall Fescue would prefer sandier loam for deep roots (TTTF can root 3 feet in perfect sandy loam conditions). But this comes to mind right now - Yes the clay and silt in loam holds moisture for the plant's roots to use - but compost/organic matter probably makes it easier for the roots to receive that water compared to clay which holds onto water better instead of giving it to the roots - but again, compost ultimately just disappears though - If I tilled in yards and yards of compost right now, in some years it would eventually be all used up by the plants.


I was surprised not to see any worms in about 4K sq ft of tilling, a few were found previously but not many. Before tilling, the ground was hand dethatched to pull out rocks etc, and then a gas dethatcher was ran to rip out all of the top growth and some of the crowns of the mostly/all crabgrass lawn that was there - So maybe this scarred the worms deeper than the 10" tilling depth, or scarred off to the side yards?

(side note: if tilling and not roundupping anything, my theory is to scalp out as much of the existing lawn/weeds so that their green lively blades don't get mixed into the tilled soil and then soon decompose right next to where new grass roots are sprouting - as if to say that when the tilled-in grass decomposes it could spread that decomposition/composting onto the newly forming grass roots and kill them (partly). I've done it both ways though no problem really I've even skipped the bagged scalp mowing and just tilled tall grass and weeds right in and new grass came in thick. BTW, the only weeds/plants present were basically %100 crabgrass which may need to be spot sprayed next summer when the seeds from this year sprout (or use a pre emergent but I'm in the no preEm camp). If there were lots of broadleaf and perennial plants, I would suggest roundupping since they could grow right back even if chopped up and tilled in.) Just wanted to explain how maybe the thatcher could have scarred worms away but I don't think so anyway. I think it's because there was no turf grass, just annual crabgrass which doesn't have a permanent root system worms might need.

So anyway, it was tilled and that was the only chance to get organic material as deep as possible compared to topdressing compost after a more shallow core aeration once the lawn establishes.

So in terms of worms, I know they only eat plant matter, but it's not to say this site is completely void of plant matter even though the soil is light brown. There are 2 large maples about 50 ft with lots of webby feeder roots just below the surface. So I guess worms could eat those but probably they prefer softer/easier food like grass roots and there was basically no perrennial turf grass there, just Crab Grass which is only alive basically 1/4 to 1/3 of the year vs perrenial grass roots are always there - hence possibly why there were no worms (and come to think of it, the few worms which were found were at the edge where there is some perennial fine fescue).

EDIT: " Under normal conditions, feeder roots die and are replaced on a regular basis "

^ which WOULD make it easy for worms to eat, so who knows why there were no worms found? But it could still be that worms just prefer grass. Also this is good news because the tilling did destroy/remove quite a bit of the fine stringy feeder roots, done it before but not quite as much, there were some casualties also on some thicker 1-2" roots but not enough to worry about with trees this size IMO. - Original plan was to only till where there were no roots and then slice seed the rooty areas, but tilling wasn't too bad in the rooty areas and I wanted to loosen and aerate as deep as possible which is what the tiller does and not a slice seeder even if I ran the slicer slow and deep in a grid pattern to basically till just the top couple inches.

what I'm getting at is this:

Once the grass and its roots get established a year or two, and then the grass clippings and maple leaves are mulch mowed instead of bagged thus creating a top layer of organic matter, is it then that the worms will basically thrive and eat this compost and bring it down deeper (a foot or more maybe several feet [turf type tall fescue can root up to 3 feet in perfect conditions]) and poo it out and create that forever composting cycle bringing compost nutrients to the deep root zone?

In other words, the theory is correct that if I till compost 10 inches down (about max tiller can reach), and if there are no worms, the lawn would just eat up that compost and it won't last long. Compared as mentioned - first get the lawn and roots established and mulch clippings and leaves and then incorporate (order online) garden worms into the soil and they will do the composting to the deeper rooting zone?

I would like to add worms now but seeing how light brown the soil is and not high in organic matter which worms eat, I'm thinking they might just die off or leave. Plus I added 5lbs of sulphate of potash since the soil was low in K and I'm not sure if that'd kill the worms. (the soil happens to be high in nitrogen and phosphorus though as if things were mulched or leaves [phosphorus] were left to compost)

Also, the house about 40 years old was newly purchased and I'm surprised the soil is so light in color even near the surface as if it were never mulch mowed and as if the many many leaves from 2 large trees were always hauled away. Especially since there was no turf grass lawn and was almost all Crabgrass which is kind of hard to believe was cared for by previously always being bagged and the leaves too resulting in a light brown top soil layer.

any thought or suggestions? THANKS

EDIT: I Was going to say that regardless that clay and silt in loam hold onto nutrients and water like compost does, that compost does that too but allows more beneficial air into the root system compared to clay which block air and is bad - But this is a sandy loam and the sand allows air through possibly as good or better than compost.

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