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One of the more strange methods of creating home-made fertilizer has come with some surprising results.

A recent study conducted at the University of Kuopio in Finland showed that human urine combined with wood ash can help the growth of tomato crops. Separately, these two ingredients have been used in fertilizers for centuries, but no one ever thought of combining them until now. Surendra Pradhan and Helvi Heinonen-Tanski collected urine, stored it at 45 degrees F (23.4 C) for 6 months and then added wood ash taken from a home furnace.

The scientists conducted three different experiments for the study:  one group of tomato plants used a commercial fertilizer; a second group used a combination of urine and birch ash, and the third simply used urine. The group of plants fertilized with the urine and ash compound yielded 4 times more tomatoes than non-fertilized plants; commercialized fertilizer yielded 5 times more than non-fertilized, and the urine alone had slightly better results than if it were combined with ash. However, the urine and ash fertilizer also provided much larger plants and tomatoes with higher levels of magnesium; which is good for bone, muscle and heart health.

The plus side to using this process is that it is very simple and the ingredients are extremely easy to obtain. Researchers estimated that a single person’s urine could fertilize over 6,000 tomato plants per year, yielding over 2 tons of tomatoes. The ash would then be applied three days or more after applying the urine.  According to Pradhan, “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”.

The downside, however, is that hormones or pharmaceuticals found in urine (such as birth control pills and other medicine) could have a negative impact on the crops. These things can be absorbed by the plants themselves and promote antibiotic resistance. Also, being that plants are usually very salt-averse, the saline content of urine could be harmful at high enough doses.

This method of combining human urine with ash for fertilization may seem a bit strange, crude and even unsanitary. If it’s any consolation, a group of 20 taste testers found tomatoes grown by all experimented methods to be equally tasty. Maybe you will think twice before you eat tomatoes or tomato based foods again, due to the possibility of using these natural items as fertilizer; but if you think about it, it’s probably much healthier for you than the chemical-based alternatives.

About The Author: Heidi Marshall

I started writing for GF in 2009. After writing over a thousand articles and a bit of a hiatus, I'm back! When I'm not writing, you can find me out for a walk, working in my garden, or making a variety of green crafts.


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