Agriculture Reference
In-Depth Information
some of the microbes that need oxygen are buried, killing many of them. Conversely,
some of the microbes that can't live with too much oxygen are brought to the surface,
killing many of them. Tilling causes miles and miles of beneficial fungi to be sliced into
pieces. Those fungi provided important nutrients to the plants, which no longer happens
after tilling. Earthworms are also killed and their tunnels destroyed. Despite what we may
have heard as kids, cutting a worm in half doesn't make two worms — it makes one dead
worm, or if you're lucky, one injured survivor.
All of these critters had taken a long time to find the perfect spot for themselves in the
soil. They worked day and night to build themselves little homes and communities. It can
take years for this to happen, and tilling destroys that all very quickly. Perennial flowers,
shrubs and trees prefer fungal-dominated soil, so if we're trying to establish a shrub
garden or grow trees, it makes sense to leave the mulch on the surface rather than tilling it
in. If we till our gardens, we destroy many important fungi, resulting in a bacterial-domin-
ated soil. This is more conducive to growing annual vegetables, but we still want some
fungi in these soils, too.
Another potential problem that is often overlooked is the effect on the soil nutrient ra-
tios. When compost and organic matter are left on the surface, they are broken down
much more slowly than when they are tilled in, so the effect on soil nutrient levels is not
so drastic. When they're tilled in, however, if they are high in certain nutrients such as po-
tassium, they can throw the nutrient ratios off and cause problems.
Another big problem is that soil structure can be decimated if the soil is too wet, espe-
cially with clay soil. Tilling your garden when it's wet causes long-term structural damage
to the soil that can last for years. It's much better to wait a couple of weeks and plant late,
rather than working wet soil.
While the initial influx of air and water after tilling breaks down the organic matter
more quickly, and releases nutrients that allow microbes and plants to flourish for a short
time, that organic matter is oxidized faster than it is replenished. Annual deep garden
tilling without adding more organic matter will cause a decrease in organic matter in the
soil. This decreases soil fertility, nutrient-holding capacity and water-holding capacity,
and hurts soil structure. If the soil is left bare, it can crust over so that water runs off and
causes erosion instead of infiltrating.
So we can see that tilling has advantages and disadvantages. Tilling can be successful
in vegetable gardens over the long term if organic matter is brought in at the same time.
No-till and sheet mulching can be successful over the long term, especially if the soil had
some humus to start with. I think the main reasons people place themselves strictly in one
of these camps or the other may be because one theory makes the most sense to them, or
because they've had success using one method in their garden.
The bottom line is that one of the methods will work well in your garden, and a com-
bination of the two may even be optimal. I may till in some compost in the beginning if
