Hearty Tomatoes Using your Bladder and Fireplace
by Tony Isaacs
Gardeners who want to grow hearty
tomatoes may be surprised to find that they can turn to an unusual and free
source of fertilizer no further away than fireplaces and their own bladders.
Scientists from the University of Kuopio in Finland recently found that wood
ash and human urine perform equally as well as more expensive mineral
fertilizers for tomatoes and some other crops, while being more
In a study published in the Journal of
Agriculture and Food Chemistry, a team of Finnish researchers raised a
healthy crop of tomatoes in a carefully controlled series of laboratory
experiments. The researchers found that sprinkling tomatoes with human urine
mixed with wood ash produced bumper harvests when compared to untreated
plants, in some instances producing crops up to four times larger.
Although scientists have previously tested urine on plants, this is the
first one to mix it with wood ash. The combination of the two is rich in
nutrients, nitrogen, phosphorus, potassium, calcium and magnesium and
reduces the acidity of soil. According to report author Surenda Pradhen, the
new findings could lead to a new source of cheap fertilizer without the need
to use potentially dangerous chemicals.
Staed Pradhen, "the results suggest that urine with or without wood ash can
be used as a substitute for mineral fertilizer to increase the yields of
tomato without posing any microbial or chemical risks."
In the greenhouse test, tomatoes were grown with urine alone, the
combination of urine and ash and with commercial mineral fertilizer. Urine
alone actually produced more tomatoes than urine with ash did - and both
treatments performed slightly below neither the researchers' mineral
fertilizer. However, both urine-based fertilizers roughly quadrupled fruit
production when compared to unfertilized control plants and the addition of
ash resulted in larger plants and fruit and significantly higher magnesium
and potassium content. A panel of 20 taste testers rated all growing methods
as equally tasty.
The researchers estimate that a single individual's urine could fertilize
6,300 tomato plants a year, yielding more than two tons of fruit.
The idea of using urine and wood ash is not exactly new. Both have been used
in helping plants grow, and their benefits appear to be complimentary. Urea,
a commonly used nitrogenous fertilizer, is abundant in urine and wood ash
such as was produced by the birch used by the Finnish group is rich in
nutrients that urine lacks, such as potassium and calcium.
In 2004 Finnish researchers found that fertilizing with urine produced
similar or slightly better results than commercial fertilizers when used on
cucumbers. Later, in 2007, Finnish researchers found that urine
fertilization produced slightly higher growth and biomass than conventional
fertilizers for cabbages. In both of those previous studies the researchers
found no recordable hygienic threat from microorganisms. Other research has
shown that human urine is an effective substitute for synthetic fertilizers
for several crops in addition to tomatoes including cucumbers, corn,
cabbage, and wheat.
Some cautions: Plants are often highly averse to salt, thus the salinity of
urine could be harmful at high enough doses. Plus, it would probably be a
good idea to use only the urine of people who lived healthily and were not
taking medications to insure that toxins and other drugs were not passed
along - or else measure for such items. Though the study found that using
urine does not carry any harmful microbes or risk of disease, the
researchers did caution that care should be exercised to avoid direct
contact between urine-based fertilizer and the plants themselves.