In 2019 I engaged in a conversation with my garden, asking
it to answer a question I posed to it about the effect of using a homegrown
source of nitrogen, aka urine, to replace the cottonseed meal that I had used
in the past. A scientist would call my approach a simple application of the
scientific method. As I related in the previous post, the conversation amounted
to applying the usual re-mineralization mix, formulated to address deficiencies
found in the March 2019 soil test and including cottonseed meal as usual as the
nitrogen source, on one of the three beds of dent corn that I grew last year.
This bed served as the control bed. For each of the other two beds of corn, I
made one change in the planting conditions compared to the control bed: for one
bed I replaced the cottonseed meal with urine but kept all the other components
in the re-mineralization mix the same, for the other bed I used the same
re-mineralization mix but planted three days later. When I harvested the corn,
I kept the corncobs from each bed in separate locations and shelled each pile
of corncobs separately, so that I could measure the yield of the corn that grew
in each bed. I also made observations of the plants and the cobs in each bed
during the growing season. This allows me to assess what the effect of that
single change was on the yield and on any other observable changes among the
plants in each bed.
Since I’m working with living plants in a living world,
interpreting the results of such an apparently simple test really isn’t that
simple. There are quite a few things that might not have been uniform between
the three beds. And this doesn’t address more subtle differences, such as the
fact that I knew which beds got which treatments, meaning it isn’t even a
single-blind test. My hopes for what the test would reveal may have influenced
the results. US society officially doesn’t accept that nonphysical causes, such
as my thoughts, could have physical effects, but this has been shown to occur
often enough in the medical field that only the double-blind test, where
neither the patient nor the researcher knows who gets the drug or the placebo,
is considered to provide reliable results. Beyond that, a host of other subtle effects are creating considerable difficulties in accepting the results of
studies in the medical field. I mention this because I want you to understand
why I consider the result to be more tentative than it may appear when you look
at the data in the previous post.
Let’s look more closely at why I asked the garden about
using urine as a home-grown nitrogen substitute last year. Cottonseed meal
works well as a nitrogen source in my garden, and at the moment it’s readily
available. And not even from all that far away; I’ve seen cotton fields in far
southeast Missouri, and there are plenty in Arkansas just to the south.
But even though it works, and it’s readily available, it
comes at a price. The price is most obvious when I pay for it, and when I have
to haul the 50 pound bag of meal out of the car and into the basement. But that
doesn’t account for other costs incurred in growing the cotton and getting the
cottonseed meal to me.
Cotton demands a highly fertile soil. Without adding
fertility, cotton-growing will render the soil it’s grown in infertile within
only a few years. The fertilizer business demands a lot of diesel fuel and a
lot of natural gas to produce the nitrate fertilizers the commercial growers
use. (No, I don’t use organic cottonseed meal. There is so little organically
grown cotton in the US that it’s prohibitively expensive to buy organic
cottonseed meal.) There is more diesel fuel used to power the machinery that
prepares, plants, maintains, and harvests the fields, and more used to process
the cottonseeds into dry meal, and more to get that meal to me. All of that
burned fuel adds to the pollutant load of the atmosphere and contributes to
fossil fuel depletion. Any nitrate added to the fields over what the cotton
needs to grow adds to the pollutant load of the rivers that drain
cotton-growing country, most of which drain to the Mississippi River and
eventually into the Gulf of Mexico, contributing to the dead zone there. If I
could find a source of nitrogen that is closer to me and eliminates most if not
all of the fossil fuel use and associated pollution, I would love to use it.
And if in addition it is free and using it avoids a source of pollution, then
what could be stopping me from using it?
As it happens, there is a free, local source of nitrogen in
a form that plants can use, which requires almost no fossil fuels to collect
and apply, and which avoids the more usual fate of that source, where it
becomes a problem to solve. That source is urine. It’s free for the collecting
and applying, which can be done in a low tech, nearly fossil fuel free manner.
As long as I avoid applying more than the plants require for growth and I take
precautions to keep it from running off into the local stream, it will be taken
up and used and not cause pollution. As long as I only collect it when I’m
well, it won’t have the potential to cause illness. Not sending that urine into
the sewer system means that it won’t require energy to process before dumping
it into the river, nor will any byproducts of that process pollute the river.
And using it closes a loop which runs from the land to me and back to the land
again. Animal urine is part of the nitrogen cycle that keeps Earth and its beings alive.
A simple calculation I did last year indicated that I
generated enough nitrogen in urine to only need to collect and apply it once
every 10 days to one corn bed to provide enough nitrogen for that bed for the
entire growing season. Then I wanted to know if theory and the physical world are in agreement. Thus I devised and
carried out the simple scientific experiment that I briefly described above. Corn
is a particularly nitrogen-hungry crop, so if substituting urine for cottonseed
meal works for corn, it should work in the rest of the garden as well. The data
I collected suggest that urine was a successful substitute for cottonseed meal,
with the caveats I mentioned above.
With this information in hand, I will expand the use of
urine to the entire garden in 2020. Here I’ll discuss how I’m collecting and
applying the urine, how much nitrogen an adult human produces in a day in
urine, and how large a garden area that urine can supply nitrogen to.
I have already discussed health and environmental issues to
be aware of when using urine. There is also a psychological issue which arises
from the known health hazards of urine and from its association with feces: many
if not most people consider urine dirty and dangerous and won’t want to eat
anything grown with it. Urine is illegal to use on any food crops grown for
sale because of the health and environmental risks associated with
inappropriate use. If you were to consider using your own urine to supply
nitrogen for your own garden (not that I am suggesting you should), you must
first ensure that none of the food you grow with it is sold. Second, you must
ensure that you yourself, and anyone who is eating the food you grow with it,
knows you are using urine and favors its use. Informed consent is just as
important in this case as it is in sex and medicine. Third, you must ensure you
are applying the right amount, to avoid pollution of surface waters from any
excess urine that cannot be used by the soil and the plants.
In my own case, my husband Mike and I favor its use, and I collect
it only when I’m healthy. I use a plastic urinal such as are sold in pharmacies
for collection (those of you with more exposed genitalia can collect it in any
suitable container), dumping the contents into a larger lidded plastic
container for storage. I pour the day’s collected urine (roughly 2 quarts) into
a 2 gallon watering can and add water to fill the can. Then I sprinkle the
contents of the can on whichever 100 square foot bed is to receive the previous day’s
urine, following that with another 2 gallons of collected rainwater. The
plastic urinal, storage container, and sprinkling can required some oil to make
and to ship to me, but no more to use. Since I’m careful to apply only as much
urine as the plants need, and I keep that urine out of the local sewage
treatment plants, the urine turns a problem – nitrate pollution – into a
solution – home-grown soil nutrition, which in turn feeds the plants I grow.
The garden is surrounded by mowed grass paths and many square feet of
unfertilized groundcover (a mix of lawn grasses and weeds) and trees beyond, so
any nitrogen the garden or the grass paths cannot use will be absorbed and used
just beyond the garden fence.
How do I know how much urine is the right amount to apply?
First, I need to know how much nitrogen the plants I’m growing in the garden require. Agricultural scientists have done exhaustive experimentation to answer this
question and produced tables like the one available here (page 8). A glance at the table
shows that crops vary in their need for nitrogen, with potatoes and cabbages
needing a lot more than, say, turnips. If I wanted to, I could calculate
exactly how much urine I should apply to the area of each crop that I grow with
the data in this table plus knowing how much nitrogen the average adult
urinates in a day plus the square feet taken up by that crop. But in practice,
I applied the same amount of cottonseed meal to each bed except for the potato
bed, which received twice as much as the other beds. Since I know the weight of
cottonseed meal I added to each bed and the percent of nitrogen it contains, I
know how much nitrogen it added to each bed. Thus I’ll add the amount of urine
that provides the same nitrogen as the cottonseed meal I used previously,
except that I’ll add twice as much urine to the potato bed as I do to the other
beds. In later years I will consider refining how much I apply according to the
nitrogen need for each particular crop.
Here is the calculation I did in case you are curious about
how you could do this in your garden (not that I am suggesting it, of course).
From Steve Solomon’s book The Intelligent Gardener and the current version of
the worksheets in the book, which you can find here, we note that the percent
nitrogen in cottonseed meal is given as 6%. Since I know that I apply 6 pounds
of cottonseed meal to each bed (12 pounds to the potato bed), the amount of
nitrogen in the cottonseed meal is:
6 pounds * 0.06 =
0.36 pounds of added nitrogen to a 100 square foot bed
12 pounds * 0.06 =
0.72 pounds of added nitrogen to a 100 square foot bed of potatoes
In order to know how much urine to apply to each bed, I need
to know how much nitrogen an adult human produces in that person’s urine in a
day. Carol Steinfeld in Liquid Gold tells us that adult humans produce about 11
grams of nitrogen in a single day’s urine. Since there are 453 grams in a
pound, if I divide 11 grams by 453 grams per pound, I will get the amount of nitrogen
in a day’s urine in pounds:
0.024 pounds of nitrogen excreted in urine each day
Now you need the length of your growing season in days; that
multiplied by the amount of nitrogen in urine per day tells you how much
nitrogen your urine can supply during the growing season. My growing season is
about 180 to 200 days long. Using 180 days for my growing season, here is how
much nitrogen I can supply to the garden if I collect it every day and apply
all of it over the course of the growing season:
180 days * 0.024
pounds of nitrogen per day = 4.3 pounds of nitrogen
Above we found that each 100 square foot growing bed needs
0.36 pounds of added nitrogen, or 0.72 pounds if it is growing potatoes. If I
divide 4.3 pounds of nitrogen by 0.36 pounds needed per bed, I know how many
100 square foot beds a growing season’s worth of urine will supply with enough
nitrogen for good growth:
4.3 divided by 0.36 =
12 beds
I grow a total of 9 beds of vegetables and grains in the
vegetable garden. Since the potato bed needs twice as much nitrogen as the
other beds, then I need to supply the equivalent of 10 beds. I have 12 beds’
worth of urine, so I can supply all the nitrogen my vegetable and grain beds
need over an entire growing season on just my urine. In my day planner I will
keep track of which bed I add each day’s worth of urine to. In practice, each
bed only needs urine applied when it has plants growing in it that haven’t been
fully harvested, and I won’t apply urine any time the soil is soaked from rain,
so I will add somewhat less than I have calculated above. I’ll keep track of
yields as I always do and also observe each crop as it grows and make notes
about any changes compared to what I’ve seen in past years. And I’ll report the
results in 2021.
Besides this conversation, I’ll engage in some others. One
of the questions I’m asking the garden in 2020 will be if it makes sense for me
to direct-seed lettuce and some cabbage family crops in spring instead of growing
and planting seedlings. Mike and I have been eating salads almost every day,
but I haven’t been growing enough salad crops to supply anywhere close to what
we are eating. I’d like to see if I can do better this year by direct-seeding
and eating thinnings. I’ll try two separate sowings of these crops in spring,
to see if I can prolong the spring salad season. I’m also trying to grow endive
this year and some different varieties of crops than the usual ones I grow. And
with that I’ll leave you till next month and wish you bountiful harvests in
2020!
