Thursday, June 1, 2023

Gardening: Topsoil Fertility


If the yard around your house is typical suburban land, its topsoil if there is any, consists of 90% mineral material and 10% organic matter in various stages of decay.

True topsoil is about 6 inches deep, black, and here’s the caveat in southern Denton County, the consistency of bread crumbs.

Most builders remove it to set house foundations on clay subsoils.  That lost topsoil harbors microbes, bugs, and worms that set up housekeeping, make room for air and water, and use the shallow layer for a septic tank and graveyard.  Plants love to wiggle their roots in this damp, tasty part of suburbia.

The soil animals’ job description is to burrow around, eat organic matter, use the chemicals they need then excrete the leftovers, and donate their remains to the topsoil factory.  Without them fruits and vegetables, not to mention other landscape plants, are spindly and yellowed.  Never mind about great produce.  If you’re guessing a gardener’s main job is to feed topsoil’s beasties, you’re right.

The garden cycle is feed the animals that feed the plants that feed you then start over again.  This brings us to the topics of composts and fertilizers.  Despite having similar functions in the garden there is a big difference between a bag of commercial fertilizer and a bag of compost.

That sack of plant food you buy contains fast acting nitrogen, phosphorus, and potassium, also known as N, P, and K.  It accomplishes one thing, and that is to feed plant life until the cupboard is bare.  It’s a short-term garden fix, but if you listen oh so carefully you’ll hear soil animals singing a song called, “What about us?”  Some gardeners have mistaken the singers for fairies.

The big drawback to commercial fertilizers is that long-term they don’t replenish soil fertility or contribute to good structure so it holds water and air.  Beware of animals that live in poor soil.  They’re a hungry army.  Plants don’t stand a chance, and you’ll find yourself thinking about pesticides, a second short-term fix.

If that’s not enough to keep you awake nights, commercial fertilizers contain salt which accumulates after too many applications.  A typical bag or pile of compost, on the other hand, brings oohs and aahs from animals, plants, and people, so spread the stuff around in generous layers, add water, and start making your own topsoil.  Winter’s the perfect time to add compost to your garden.

If you’re new to the plant growing game, organic matter is leaves, twigs, animal manures, grass clippings, wood chips, bark, paper, and kitchen vegetable waste.  Bits of gravel now and then are okay.  Keep in mind the following limitations.  Flies love to lay eggs in oils and fats, and that means maggots.  I’m not saying flies and maggots don’t have their places in the ecosystem, but maybe not in a backyard.  Fido’s fabulous nose can sniff out buried meat scraps and bones, and he’s a natural digger, so put those down the garbage disposal or out for the trash truck.  Lastly, American gardeners don’t use carnivore manures which contain toxins better left untouched.

You can add compost to a garden any time of the year, so don’t let cold days stop you from getting a little exercise.  Pile on the raked leaves and grass, grab the spade and turn the stuff under or use it as a blanket of mulch.  Golf courses do a nifty trick with compost they call “top dressing.”  They spread compost right on top of the grass, water it in, and in no time flat the lawn grows over it while decomposition happens below the green surface.


Contact Noelle at [email protected]

Noelle Hood
Noelle Hood
Noelle is our Resident Green Thumb and a Texas Agri-Life Master Gardener.

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