gardening with wood as fertilizer
The soil in my garden dries out too much during the hottest, driest
parts of the summer. The soil is only about a foot thick. Under that
is about 4 inches of clay, then shale. Even if the soil is soaked by
a summer thunderstorm, a week or so of rainless, hot weather and the
garden plants start to suffer from lack of water. If I try to use
water from my well, the well will go dry before the plants are
supplied with enough water.
So in the fall of 2007, I moved a few remaining garden plants out of
the way and went to work with a 36 horsepower tractor fitted with a
scoop for digging earth. The scoop mounted on the 3 point hitch
system used for attaching implements such as plows, corn planters,
and other farming attachments.
About a month later and after around 20 hours work time and about $50
dollars in gasoline, half of my garden was a hole 16 feet wide, 60
feet long, and 3 feet deep. I had scraped the soil to the side out of
the way and removed over a foot and a half of the shale. The shale
holds very little water. To get the maximum amount of water storage,
the shale would be replaced by soil. Some of the soil to replace the
shale came from an area besides the garden. That soil was scraped to
the opposite half of the garden, for now in a large mound. In its
place I put the shale taken from the hole.
The idea is to have at least 2 feet of soil where previously there
had been about 16 inches counting the clay. That increases the water
holding capacity by maybe about a factor of 2. The mound of shale
taken from the hole and placed at the side of the garden has been
sloped. In summer, a tarpulin is laid on the slope to direct rain
water to the deep soil area. The area covered by tarp is about 10
feet wide and 60 feet long. That should about triple or quadruple the
amount of water the drought resistant part of the garden will
receive. Typically in my area a 1-inch thundershower occurs once
every 10 days or so in July and August. The water running off the
tarp from those summer rains along with the added storage capacity of
the deeper soil improves the production of the garden during the hot,
dry parts of the summer.
I'm guessing that no one is smart enough to know what the effects of
global warming will be. My intuition tells me there will be a very
slow, barely-noticable-to-most-people, worsening of drought in my
geographical area. But it could be worse than that. My hopefully-
drought-resistant garden could be a very valuable asset. Whatever
global warming does, if my rain catchment/deep soil garden works out
well for the present climate, it will have been worth it.
First the hole has dug and one-third filled in with soil. As the hole
was filled, a six or eight inch layer of soil was alternated with a
layer a few inches thick of organic matter - tree branches, briars,
tall grass, and other plant material. As it decays it improves the
soil's porosity and fertility. That helps encourage garden plants to
send their roots deep where the soil will stay moist longest and it
will encourage runoff from the tarpulin to soak into the soil.
The project took about $100 worth of gas for the tractor and
somewhere around 50 hours time. Maybe half that time was putting a
lot of tree limbs in the hole to improve the soil. I used a trailer
pulled by the tractor to move the limbs. The trailer is 4 feet wide
and 7 feet long with 2 feet high side. Filled the trailer 15 or 20
times, stacking the limbs about as high as I could on the trailer.
That's using a rope to keep the stack of limbs from falling over. A
layer of limbs was put in the hole and covered with just enough soil
to cover them. Ran the tractor back and forth over the limbs to
flatten them out before pushing dirt over them. Three such layers were
made. Before putting the 4th and last layer of dirt in the hole,
a layer of leafs, chestnut burrs, and twigs was spread on top of the
3rd layer of dirt.
Well, here's how the garden project turned out. The first year, none
of the garden plants did well. Some produced a crop, some were almost
total failures, for example the spinach. Apparently, too much organic
material in the process of decaying is bad for most plants. And the
dirt was very hard from having mixed in a lot of subsoil clay.
The second year I dug up the top 12 or 16 inches of the soil and
mixed in fast rotting plant material such as leafs, cut grass, and
weeds. Also mixed in a small amount of compost. Plants grew better
and produced more, but still did not do as well as before. Carrots
and butternut squash tasted very bitter.
The third year I dug trenches down to 24 inches along where the rows
of vegetables would be. I filled the trenches back in with
alternating layers of small tree branches and soil to fill most of
the trench; then a layer of cut grass or leafs or weeds topped with 6
inches soil. That year the plants grew better, about as well as
before starting the project. Carrots and squash still very bitter.
The fourth year, I did the same trench procedure as the year before
except the trenches were made between the previous year's trenches,
so the entire garden would be trenched and all the soil mixed with
organic material. This year the garden did better than before
starting the project. Carrots and butternut squash still bitter.
The fifth year, I dug trenches about 10 inches deep over half the
garden. Put a layer of cut grass, weeds, leafs and whatever other
quick rotting plant material I could find. Made the layer about 6
inches deep, then shovelled on 10 inches of soil. The garden did very
well giving me more vegetables than I could eat plus filling the
freezer. Finally, the carrots and squash had no bitterness.
Apparently, too much decaying plant material with not enough humus
caused the bitterness.
Last year(2013) I made another garden to make space for butternut
squash, corn, and beans. Several passes with the tractor pulling a
two bottom plow made a trench about 3-feet wide, 8-inches deep, and
40-feet long. The trench was dug down to a depth of 2-feet using a
shovel, mattock, and pick. I hauled the shale away in a wheelbarrow.
This time the trench was downhill from an existing slope. I filled
the bottom 8- to 10-inches of the trench with large pieces of tree
trunk and large branches, sod, and dirt. About the next 8-inches was
filled with vines, small branches, briar canes, and soil. The top 6-
inches or so was filled with soil. Before planting I made furrows with
a hoe, about 4-inches deep. I filled the furrows with a mixture of
top soil and compost. Seeds were planted in the soil/compost mixture.
Also, 4 hills of butternut squash seeds were planted along the side
the edge of the strip adjacent to the slope, each hill having 2 to 3
An 8-foot wide tarpulin was spread on the slope to direct rain water
to the edge of the garden having the squash plants. I used about 1/4
cup of 12-12-12 fertilizer per hill of squash. No other fertilizer was
used. At the end of the growing season I had a bumper crop of squash,
probably about 24 large, good flavored butternut squash that supplied
all I could eat until April the next year. The beans also produced a
large crop and the corn an average to good amount.
It seems that unrotted organic material in the soil does no harm as
long as there is an abundance of thoroughly rotted material also in
the soil. Once the soil is built up with humus, it seems that adding
plant material to the soil is easier than making compost in piles,
then mixing the compost in the garden soil.
It took a tremendous amount of digging and a tremendous amount of
organic material to get all that clay subsoil into porous, rich
garden soil. Few people, I suppose, would want to go to all the time
and effort. Me, if I had it to do over again, would probably check on
getting somebody to truck in a hugh quantity of compost or wood chips
and then maybe pay somebody with a Bobcat-type machine to dig out the
hole and refill with the compost and/or wood chips and soil.
I call my experience positive. I got a lot of exercize over the last 5
years which I suppose helped my health and fitness and now have a
garden with 24-inch deep, rich soil. The deep soil better provides
moisture throughout droughts. And at one edge of the garden is the
sloped area where I lay a tarpulin to direct rain water that helps
keep a several foot wide swath of soil damp during dry summers as long
as it rains at least once a week or so.
And now I know better how to fertilize soil without depending on
commercial fertilizers. Adding organic material is a lot more work
but has several advantages. It adds humus which increases soil
porosity (probably a big advantage for plant growth), increases the
water holding capacity of the soil (a big advantage during drought),
and probably adds trace minerals lacking in commercial fertilizers.
That last factor seems likely to make the plants grow more, produce
more, and, perhaps very importantly, make the food more nutritious
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