 |
| Compost being made by Ponderosa Dairy in Amargosa Nevada by the windrow method |
Q. I hope you remember me from the last time you were in
Kingman teaching. I am a Master
Gardener. My question involves
composting in the home garden for spring planting. There seems to be no definitive answers as to
when is the best time to add compost to the garden, and exactly how much
compost to apply. I hear that it may be
better to apply the compost before the first frost so that it has time to break
down before spring planting, and then again I hear that you should add it maybe
a month or so before you plant. The
latter is normally the approach I take.
So far, so good, but can you share your thoughts with me on these two
topics? Thanks.
the soil to determine how much compost to add. For instance, a dark rich soil
that crumbles easily will need less compost than one which is hard to dig and
does not crumble easily. A well prepared vegetable bed should be so friable
that you can dig it nearly with your hands, unaided by a shovel. This kind of
soil structure we call “crumby” like cake crumbs.
 |
| Compost being added to the vegetable plots at The Orchard in North Las Vegas |
Once we achieve this state in a vegetable garden soil we
just need to replenish the organic matter which was lost during the growing
season. Generally we figure that we lose about 1/3 of our organic matter
content of our soil each year. So the first year it is 1/3 of our total organic
matter content. The second year it is 1/3 of our remaining organic matter
content, etc. So you see it will not run out
in three years to zero. It will
continue to diminish annually but at a different rate as the total amount of
organic matter diminishes.
garden it will take about three years of applying a heavy amount of compost to
the soil each year. These applications of compost must also be accompanied by
growing vegetables in it. Just putting a compost into a soil and doing nothing
else and waiting for three years will accomplish absolutely nothing. Water and
microorganisms must be in the mix as well. I like to compare it to making bread
or a cake. You can add all the dry ingredients to a bread or cake mix you want
but without adequate liquid they will sit there and do nothing.
less than 1/10 of 1% organic matter. That is amazingly low. In other rawvdesert
soils the organic matter may reach 3 /10 or 4/10 of 1%, still not much. We want
our soils to get to 5 to 8% organic matter. This is 50 to 80 times higher
amounts than we have. To achieve this I like to add a minimum of 50% compost to
our raw desert soils. I would even push it higher, closer to 75% the first
year. Every time the soil is prepared for a new planting, organic matter or
compost should be added. It does not matter the time of year in the warm
climate of Las Vegas. In colder climates when soil temperatures drop into the
40’s, most compost will sit there and not do much. As soon as the soil
temperatures hit the mid 50’s the microorganisms will kick in and start to
work.
 |
| Yes, this is my foot on top of a desert soil typical of what we would use for vegetable production. It is modified heavily with compost over a three year production cycle. |
is then ready to release all the goodies that was built up into it during the
composting or rotting process. So if a compost is a finished compost it will
not continue to decompose. This is not true of unfinished composts or manure.
These will continue to “rot” or decompose and they create their own
heat when they do so and are piled together into a pile. Heat builds in the
center of the pile to over 160F which is what you need to start killing weed seeds
and bad plant pathogens.
amount varies with the color of the soil. Darker, rich soils need less than
lighter colored less well developed garden soils. But if you add compost every
time you plant and you continuously garden for three years in it, then the
garden soil will be sustainable with small amounts of compost every time you
plant. I hope this helps.