Wednesday, August 24, 2016

An Interesting Source for Organic Fertilizer

Over the years, a number of our F2F volunteers have worked in the area of soil fertility. As synthetic agro-inputs can be pricey, oftentimes our volunteers teach hosts about organic soil fertility management practices such as the use of green manures, compost, companion crops, crop rotations, and animal manure. One common and inexpensive source of macronutrients, however, frequently gets overlooked: urine.

Stored goat urine at CEPROCAL
In March 2016, F2F volunteer Rob Crook traveled to Guatemala for a two week assignment to train extension agents with the Center for Goat Production in the Altiplano of Guatemala (CEPROCAL) on how to make liquid fertilizer and compost using goat urine. CEPROCAL currently captures and stores the urine produced by stabled goats at their production center. While CEPROCAL technicians have speculated that the urine is an excellent source of nutrients for fertilizing home gardens and pastures, they did not know how to best utilize it and in what quantity. After working with CEPROCAL technicians over the assignment, Crook recommended that CEPROCAL takes fresh and stored goat urine samples to analyze the difference in nitrogen content (due to volatilization). Additionally, he recommended that they conduct several independent variable experiments with goat urine on pasture and row crops to better understand the effect that the urine has when applied directly as opposed to using in compost. After conducting the experiments and analyzing the samples, CEPROCAL extension agents will in turn teach rural families and beneficiaries of the program how to use the organic fertilizers for improved pasture and vegetable production to supplement and diversify the family diet.

It is important to note, however, that all urine - including human urine - contains valuable macronutrients and micronutrients that can be used for crop production, especially a simple home garden. While using human urine may be viewed as an unpleasant concept at first glance, the potential benefits are undeniable. The primary macronutrient found in urine is nitrogen. Additionally, that urine contains anywhere between 2.5 and 3.5 grams of potassium and 0.5 to 1 gram of phosphorus in plant soluble form. Worried about urine acidifying your soil? Fresh urine typically has a pH that hovers around 6, while stored urine often becomes moderately alkaline.

Stabled goats at CEPROCAL
Ok, so it has macronutrients and won't substantially mess with the soil's pH, but is it safe to use? Actually, yes. Human urine - except in very rare circumstances - is sterile when it leaves the body. According to the World Health Organization (WHO), the few pathogens that may be transmitted through urine are not considered a major health risk, especially in temperate regions.

Right, right, so it's safe to use, but what about the smell? That strong smell is due in large part to the volatizing nitrogen in the urine as it comes in contact with oxygen. In other words, storing the urine in a hermetically sealed non-corrosive container will greatly limit the odor. Additional steps taken during the application (described below) will further reduce any foul odor.

How much should be applied and what is the best method of applying it? As the quantity of nitrogen in urine varies (as do plant nitrogen requirements), using trial and error with dilution rates and frequency of application is critical. It should be noted, however, that studies conducted by ECHO with corn, okra, and pak choi, indicate that the plants that received a 9:1 water to urine application rate once a week performed the best. Preferably shortly before rainfall, the diluted urine should be poured into 1 to 2 inch furrows and covered with soil shortly thereafter.

For more information about sustainable and sanitary human waste technologies, please visit

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