Yesterday, I had a conversation with someone while dropping
off some compost. That person was
concerned about the productivity of the garden and its relationship to the
soil. We looked at some garden beds and
saw a typical situation. The plants are
alive and look reasonably healthy, but the soil does not look the same. The bed (4’ x 10’) has the typical structure
of about ½” of mulch on top, then about 1-2” of a sandy compost mix, and then
soil. When I dig into the soil, it is
compacted and tough to dig through. I
don’t see any signs of soil life such as worms, worm holes or little bugs
crawling around. I don’t see any signs
of decaying organic matter. That means
the important things of nutrient cycling, carbon cycling, water cycling/holding
are weak or maybe not happening at all.
An ideal soil has a lot going on. It is dynamic like our bodies. It is a living thing. Think of it like your spouse – beautiful and
a mind/system of its own. Ideally, it would
be 25% air, 25% water and 50% soil composed of living things, decaying food
scraps, minerals, old soil and mulch in a 3-4” band across the top of the soil,
and preferably deeper.
In
his new book, Organic Management for the Professional -- Howard Garret of
Dallas, Texas’ top organic gardener is recommending 4-6” of mulch on top. Think of mulch as SPF cream or
moisturizer. In a region that evaporates
2-3x more moisture than we receive in rainfall (excl. dew/humidity) as compared
to regions in the USA that evaporate 0.5x their rainfall (coastal forest
areas), we need to capture and hold as much moisture from the dry hot winds,
and high UV as possible. Mulch keeps
your soil alive at the upper soil levels by preventing the UV from reaching the
soil. More importantly, it sequesters
the moisture down low where the hot dehydrating air cannot pick it up and carry
it off.
The answer at the end of the conversation was not to add
more compost, but to turn the top layers of the mulch into the compost. Make the mix fluffier instead of so
dense. Next we will try to get more life
working in the soil as well as look at minerals/nutrients. Before the end of the fall season, I hope to
add more mulch on top of the soil to prepare it for winter.
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