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For other uses, see Guano (disambiguation).

The Chincha guano islands in Peru. February 21, 1863.

The nest of the Peruvian Booby is made of guano.

Mining guano.

Guano (from the Quechua 'wanu', via Spanish) is the droppings of seabirds, bats, and seals ^[1].

It is an effective fertilizer and gunpowder ingredient due to its high levels of phosphorus and nitrogen and also its lack of odor. Superphosphate made from guano is used for aerial topdressing. Soil that is deficient in organic matter can be made much more productive by addition of this manure.

Guano consists of ammonia, along with uric, phosphoric, oxalic, and carbonic acids, as well as some earth salts and impurities. Guano also has a high concentration of nitrates.

It is estimated that there is only enough phosphorus from current resources to last about 30 years. This is a problem as vast volumes of phosphorus are needed to produce fertilizer, as it is an essential plant macronutrient. Guano is rich in phosphorus and is an effective phosphorus fertilizer. It is a $1.4 billion industry.^{[citation needed]}

The ideal type of guano is found in exceptionally dry climates, as rainwater drains the guano of nitrates. Guano is harvested on various islands in the Pacific Ocean (for example the Chincha Islands and Nauru) and in other oceans (for example Juan de Nova Island). These islands have been home to mass seabird colonies for many centuries, and the guano has collected to a depth of many metres. In the 19th century, Peru was famous for its supply of guano. Bat guano is usually mined in caves. One of the major innovators in guano harvesting was Benjamin Drake Van Wissen.

Guano has been harvested over several centuries along the coast of Peru, where islands and rocky shores have been sheltered from humans and predators. The Guanay Cormorant has historically been the most important producer of guano; its guano is richer in nitrogen than guano from other seabirds. Other important guano producing species off the coast of Peru are the Peruvian Pelican and the Peruvian Booby.

The high concentration of nitrates also made guano an important strategic commodity, with the War of the Pacific between the Peru-Bolivia alliance and Chile was primarily based upon Bolivia's attempt to tax Chilean guano harvesters.

Slang usage of Guano can be traced back to the amateur ("ham") radio culture in New England, USA, during the World War II era. In that context, the slang term "guano" referred to equipment of dubious value or technological currency, i.e., often outdated, broken, or cumbersome equipment. More recently, "guano" has been used in the engineering profession, and particularly in the audio engineering profession. For example, one might say, "That man's studio is overrun with truckloads of obsolete guano." This usage remains predominantly in the New England region but it is known to crop up occasionally in other areas as well.^{[citation needed]}

• Guano Islands Act
• Feces
• Economy of Nauru

• ProAbonos
• Is there Guano in Mascara? - Good Organic Gardening Reference