Urine is a quick-acting nitrogen-rich complete fertilizer. Knowing how and when to apply urine is beneficial.
CONSIDERATIONS

Some crops, e.g. tomatoes, are sensitive to having all their roots exposed to urine, at least when plants are small, while on many crops no negative effect is seen at all. Therefore, before the sensitivity of a crop is known, it is wise not to simultaneously expose all the roots of the plant to urine, be it neat or diluted. Instead, urine can be applied either prior to sowing/planting or at such a distance from the plants that the nutrients are within reach of the roots, but not all of them are soaked. For annual plants this distance may be about 4 inches. (Jönsson, H., et al. 2004)

RATE & FREQUENCY

As a rule of thumb, a concentration of 3-7 grams of N per liter of urine can be expected (Vinnerås, 2002; Jönsson & Vinnerås, 2004).

The total applied amount of urine and whether it should preferably be applied once or several times also depends on the nitrogen need of the plant and its root size. Root size varies widely between different crops. Plants with inefficient or small root systems, e.g. carrots, onions and lettuce, can benefit from repeated applications of urine throughout the cultivation time (Thorup-Kristensen, 2001; Jönsson, H., et al. 2004, Richert, A, et al. 2010).

In order to avoid leaching, and for climates with heavy rainfall or very sandy soils, frequent application of small amounts of urine is favorable but not essential. (Jönsson, H., et al. 2004; Johanssson et al., 2001; Rodhe et al., 2004).

DILUTION

Urine can be applied either undiluted or diluted, depending on the plant’s needs. Dilution rates range from 1:1 water/urine to up to 15:1. 3:1 is the most common.

TIMING

Urine’s nutrients are best utilized if urine is applied before sowing/planting up until 2/3 -1/4 of the period between sowing and harvest. (Jönsson, H., et al. 2004)

In large-scale crop production, the normal fertilizing strategy is application of nutrients once or twice per growing season. If fertilizer is applied only once, this should normally be carried out prior to or at the time of sowing/planting. (Jönsson, H., et al. 2004)

The crop can also be continuously fertilized, e.g. if the urine is collected in smaller containers and used more or less directly. However, once the crop enters its reproductive stage it hardly takes up any more nutrients. An example is maize; fertilizer applied until the plants are setting ears is well utilized, but after this stage the uptake of nutrients from the soil declines, as at this stage the nutrients are mainly relocated within the plant. (Marschner, 1997; Jönsson, H., et al. 2004)

METHOD

The best nitrogen fertilizing effect is obtained when urine is applied close to the ground and directly incorporated or watered into the soil in order to minimize ammonia losses to the air. For example, urine can be distributed in small furrows that are covered after application.

Urine should always be applied next to the plant (in furrows) but not onto the plant. Otherwise it might lead to “burning” of the leaves. (Jönsson, H., et al. 2004)

Spraying urine in the air should be avoided due to the risk of nitrogen loss through gaseous emissions of ammonia. (Johanssson et al., 2001; Rodhe et al., 2004)

Drip Irrigation: urine could be distributed through a drip irrigation system. Water may needed to be added to ensure the emitters don’t become clogged. It’s recommended to conduct small scale tests first when using this method, to determine the appropriate water/urine ratio.

For larger fields, a tractor based liquid fertilizer dispenser could be used.

REFERENCES

Johansson, M., Jönsson, H., Höglund, C., Richert Stintzing, A. & Rodhe, L. 2001. Urine separation – closing
the nutrient cycle. Stockholm Water Company. Stockholm, Sweden. http://www.stockholmvatten.se/pdf_arkiv/english/Urinsep_eng.pdf.

Jönsson, H., Richert Stintzing, A., Vinnerås, B., Salomon. 2004. Guidelines on the Use of Urine and Faeces, EcoSanRes Publications Series. Stockholm Environment Institute.

Jönsson, H. & Vinnerås, B. 2004. Adapting the nutrient content of urine and faeces in different countries using FAO and Swedish data. In: Ecosan – Closing the loop. Proceedings of the 2nd International Symposium on Ecological Sanitation, incorporating the 1st IWA specialist group conference on sustainable sanitation, 7th-11th April 2003, Lubeck, Germany. pp 623-626.

Marschner, H. 1997. Mineral Nutrition of Higher Plants. 2nd edition. Academic Press.

Richert, A., Gensch, R., Jönsson, H., Stenström, T. and Dagerskog, L., 2010. Practical Guidance on the Use of
Urine in Crop Production. EcoSanRes Programme. Stockholm Environment Institute. www.ecosanres.org

Rodhe L., Richert Stintzing A. & Steineck S., 2004. ‘Ammonia emissions after application of human urine to clay soil for barley growth’. Nutrient Cycling in Agroecosystems, 68:191-198.

Schönning, C. and Stenström, T-A. 2004. Guidelines for the Safe Use of Urine and Faeces in Ecological Sanitation Systems. Report 2004-1. EcoSanRes Programme. Stockholm Environment Insitute. www.ecosanres.org

Thorup-Kristensen, K. 2001. ‘Root growth and soil nitrogen depletion by onion, lettuce, early cabbage and carrot’ Acta Horticulturae. 563: 201-206.

Vinnerås, B. 2002. Possibilities for sustainable nutrient recycling by faecal separation combined with urine diversion. Agraria 353, Acta Universitatis Agriculturae Sueciae, Swedish University of Agricultural Sciences. Uppsala, Sweden.