Urine makes a great natural fertilizer

All that nitrogen, potassium and phosphate in human urine makes it a great fertilizer.

Credit: Melissa Fraser

Using urine is a step towards a sustainable garden

This post started first with an interesting article that was emailed to me, then a simple Google search of “human urine as fertilizer.” It’s amazing the things I learned.

According to the article, Better Tomatoes via a Fertilizer or… Human Urine?, a study from Finland found that tomatoes fertilized with a mixture of human urine and wood ash produced over four times as much fruit as those without. The fruit also had more beta-carotene and more protein than the pee-less ones. They say it’s because human urine contains nutrients like nitrogen, potassium and phosphate, which are all great for plants.

I did a little online research to see how the yellow stuff works for the green stuff. (If you have anything to add on this, post a comment below; no need for waste to go to, uh… waste?)

  • Urine should be diluted 10-15 parts water to 1 part urine for outside plants, 30-50 parts water for inside plants, and undiluted for lawns, trees and shrubs is just fine, according to this article all about Using Human Urine As A Liquid Fertilizer.
  • The urine needs to be used fresh because as urine sits it turns into ammonia and becomes less and less nutritious for plants.
  • Apply the homemade fertilizer to the roots and spread it around. Don’t put too much in one area and there’s no need to use it every time you water.
  • If your plants are taking on a yellowish tinge or if they are not growing fruit, cut back on the urine application.
  • Use the urine on your compost. This article says urine can speed up the composting process on an otherwise dull heap.
  • Male urine works to keep unwanted intruders out of the garden, too. Sprinkle some undiluted urine around the perimeter of the are you want to keep safe to deter pests.

You may be a little hesitant to collect your own urine, but remember fresh urine is basically sterile and odour-free. Also, using urine as fertilizer is not only another step toward a sustainable garden—think of the water you’ll save by not flushing—it’s the free alternative to the store-bought fertilizer.