Seabird excrement, known as guano, is a valuable source of nutrients and has been used for centuries as fertilizer. When fresh, guano is a loose accumulation of feces and uric acid with a pungent, ammonia-rich odor. However, when allowed to dry in the open air over time, guano loses much of its smell and can be harvested and processed for agricultural use. The word “guano” comes from the Quechua word “wanu,” meaning “dung.” Quechua is an indigenous language of the Andes that was used as a lingua franca across the Inca Empire. Let’s take a deeper look at what exactly guano is, its history and uses, and the specific word used to describe this dried seabird waste product.
What is Guano?
Guano is the accumulated excrement of seabirds, most notably cormorants, boobies, and pelicans. These birds consume fish, squid, and other marine life that is rich in nitrogen, phosphates, and potassium. The nutrients are absorbed but the indigestible parts are excreted. The dry climate and lack of rain in seabird nesting sites allows the accumulated droppings to desiccate rather than be washed away. Over hundreds and sometimes thousands of years, the feces build up into mounds. Guano deposits are found down the western coasts of South America and Southern Africa in particular, as well as other seabird islands around the world.
The droppings have a high levels of ammonia and uric acid when fresh. When permitted to dry for extended periods, guano becomes a stable and condensed source of nitrogen and phosphorus. Precise nutrient compositions vary based on the seabird species and their diets. However, nitrogen levels are typically in the range of 8-16%, comparable to the most enriched synthetic fertilizers. Phosphate levels are also high. These nutrients make guano an extremely effective fertilizer when applied to poor soil.
Brief History of Guano Use
Guano has been harvested and utilized by humans for over 1500 years. Some of the earliest known use dates back to the Inca in South America in the 5th century BCE. The Incas regarded guano as sacred due to its agricultural value. Laws strictly regulated access and harvesting from offshore islands. Punishments for altering or interfering with guano deposits could include death. As a result, Incan guano deposits accumulated undisturbed for centuries.
European interest in guano began in the early 1800s. German naturalist Alexander von Humboldt first brought samples back to Europe. Analysis demonstrated its extraordinary fertilizer properties. By the 1840s, British traders were importing guano from Peru to sell to farmers. Guano imports peaked in the late 1800s before the supplies began to dwindle. By 1909, guano deposits were largely exhausted worldwide.
Today, guano is still harvested but in much smaller quantities. Current harvest methods focus on collecting only the first layers of guano to allow the seabird colonies to replenish at sustainable rates. Synthetic fertilizers have also reduced demand for guano. However, organically certified guano is still highly prized as a natural fertilizer and soil amendment.
Uses as a Fertilizer
The excrement of seabirds, especially when accumulated in dry deposits over long periods, makes an exceptional fertilizer and soil enricher with both nitrogen and phosphate nutrients. Guano contains 2-12 times more nitrogen, 6-12 times more phosphate, and 2-3 times more potassium than typical livestock manure. These are the three primary macronutrients needed for plant growth. Nitrogen in particular is lacking in many soils and critical for green growth and photosynthesis. The nutrients in guano are also more readily available for plant uptake compared to unprocessed organic materials.
When guano is applied to deficient soils, it provides nutrients to substantially increase yields of crops. Historical reports noted potatoes increased by 47% and sugar cane by 50% when guano was applied compared to using no fertilizer. Nutrients from guano also improve the quality and flavor of produce. Modern farming continues to use guano, especially organic operations looking to enrich soil naturally. Home gardeners may buy pelletized guano as an organic fertilizer. In addition to fertilizer use, guano provides benefits related to organic matter, microbiology, moisture retention, and soil pH buffering.
Current Seabird Guano Production
Global supplies of guano were largely exhausted by the early 20th century after decades of intensive mining operations. However, smaller scale, sustainable harvesting from seabird islands continues today. Current world production is estimated at around 250,000 metric tons per year. The biggest producer is South Africa, followed by Peru, Chile, and Namibia. Smaller amounts are harvested from other coastal nations including Mexico, India, and Thailand.
In terms of species, cormorant guano is the most abundant modern source. The guano is harvested from offshore islands around Namibia, South Africa, and other nations where large cormorant colonies reside. Industrial scale mining operations are not permitted. Instead, only the top layer of guano is removed from nesting areas. This allows the colonies to replenish and the harvesting to be continued annually. Typically, around 2 cm of guano is collected depending on the area.
Strict regulations govern the licensing and allocation of guano harvesting rights. In certain countries, the military may oversee guano control and distribution. Harvesting is generally done by hand using basic equipment like shovels and wheelbarrows. The negative environmental impacts and disruptions to seabird populations that occurred from past mining operations are prevented under the current sustainable harvesting protocols.
Chemical Composition
The specific chemical composition of guano varies based on the seabird species it originates from and its geographic location. However, guano generally contains 2-12% nitrogen, 2-10% phosphate, and 0.5-2% potassium, along with variable organic matter. Measured pH is normally around 8-9. Here are example nutrient analyses from different current sources:
Source | Nitrogen % | Phosphate % | Potassium % |
Peru cormorant guano | 12 | 10-12 | 2 |
Chile mixed guano | 8-10 | 12-15 | 1-2 |
South Africa cape cormorant guano | 6-8 | 4-7 | 0.5-1 |
These nutrient levels are similar to or even exceed most synthetic dry fertilizers. For example, typical synthetic 10-20-10 fertilizer contains only 10% nitrogen, 20% phosphate, and 10% potassium. However, guano has the benefit of being an organic, slow release source versus synthetic chemical salts.
Measured micronutrients in guano include calcium, magnesium, sulfur, iron, manganese, zinc, copper, and boron. The concentrations vary based on the seabird species and specific test sample. However, the trace elements complement the macronutrients to provide a broad nutrient profile that supports comprehensive plant nutrition.
Processing of Fresh Guano
Fresh guano is collected from locations where large seabird colonies actively nest. The fresh waste has an ammonia odor and needs to be processed after harvesting. Initial processing steps include:
– Spreading the fresh guano to dry. This reduces moisture to around 20-25%.
– Screening or sifting to remove any debris, eggshells, feathers, etc.
– Sanitization through extended heated drying or treatment with sodium carbonate.
The dried guano can then be milled into a fine powder. When needed for retail use, it may be pelletized along with a binder to produce spherical fertilizer pellets optimized for spreading equipment. Or it can be packaged as a powdered product. With minimal processing, guano offers an organic fertilizing option.
Organic Certification
For agricultural use, guano is typically certified for organic production. Organic guano serves as a soil amendment and fertilizer that meets the National Organic Program (NOP) standards in the United States and similar standards worldwide. Key criteria for organic certification include:
– Guano must originate from wild seabirds and cannot contain waste from birds fed prohibited materials.
– Processing aids such as drying, sifting, and pelletizing are acceptable but chemical additions or synthetic coatings are prohibited.
– Sustainable harvesting must be verified with minimal disruption to seabird populations or the environment.
When these criteria are satisfied, guano can provide a “natural” fertilizer choice for supporting certified organic crop production. Organically certified guano also can be used in backyard gardening by those wanting to avoid synthetic fertilizers.
Benefits of Guano Fertilizer
The nutrients and properties that make guano an exceptional fertilizer include:
– Nitrogen levels from 2-12% to support healthy green growth.
– Phosphate levels from 2-15% to stimulate root and flower development.
– Abundant micronutrients including calcium, boron, manganese, and zinc.
– Improves microbial life and enzyme activity in soil.
– Enhances water retention and breaks up heavy soils when added.
– pH level around 8 can help neutralize overly acidic soils.
– Slow release source of nutrients that is unlikely to burn plants.
– Complementary to most synthetic fertilizers andfarming systems.
– Approved for organic agriculture and organic gardening.
– Renewable fertilizer source when regulations on harvesting are followed.
The benefits above allow guano to excel in nitrogen-demanding uses like hay fields and lawns. It also strengthens vegetable crops by stimulating root and fruit formation courtesy of its phosphates. When blended into soil, guano improves tilth and nutrient properties for long-term enhancement. For these reasons, it has long been prized as a soil amendment and fertilizer.
Disadvantages of Guano
While guano has many advantages, there are certain disadvantages to consider as well:
– Limited and nonrenewable supply – Deposits are finite and production is capped at sustainable levels.
– Variable nutrient composition – Nutrient levels fluctuate based on seabird diet, location, and testing.
– Can develop molds and fungi – Damp, unpacked guano can decompose and get moldy though drying prevents this.
– Strong odor – Fresh droppings have an ammonia smell that requires processing or aging to reduce.
– Can harbor pathogens like E. coli – Composting and proper application is advised.
– Contains uric acid – This acidity mandates soil pH monitoring and may affect soil biology.
– May be costlier than synthetic fertilizers – But cheaper than many natural organic amendments.
While these downsides exist, none are overwhelming drawbacks when guano is managed properly. Proper sourcing, processing, and application mitigate the disadvantages while allowing guano to highlight its many soil benefits.
Optimal Application Rates
Suggested application rates for guano depend on the specific nutrient concentrations. Typical ranges include:
– For field crops, vegetables, and hay fields – 250-500 lbs per acre
– For fruit and nut trees and berries – 0.5-1 lb per tree or plant
– For lawns – 10-15 lbs per 1000 sq ft
– For gardens and flower beds – 5 lbs per 100 sq ft
Higher rates, up to 1000 lbs per acre, can be used when trying to build soil nutrients over successive seasons. For best results split applications over the growing season, such as early spring and midsummer. Pelletized guano can be spread using broadcast equipment. Otherwise a hand-cranked whirlybird spreader will efficiently distribute the powder.
Guano should not be applied at excessive rates. This could potentially burn plants or runoff. Routinely testing soil to monitor nutrients is advised with any fertilizer program including guano. An accompanying soil analysis will provide data-driven guidance on ideal guano rates for a given situation.
Combining Guano With Other Amendments
While guano supplies the primary macronutrients, additional soil amendments can complement it:
– Compost, peat moss, or coco coir provide organic matter to improve moisture retention, cation exchange capacity, drainage, and soil aggregation.
– Limestone, oyster shells, or dolomite can help balance pH levels.
– Worm castings, fish emulsion, or alfalfa meal contribute more slow release organic nitrogen.
– Kelp meal, humic acid, and molasses provide vitamins, minerals, carbohydrates, and humic substances to stimulate microbial activity and growth.
– Biochar improves retention of nutrients while facilitating helpful soil bacteria.
– Natural rock phosphate, sulfur, gypsum, greensand, and granite meal supply secondary macronutrients and micronutrients.
– Cover crops, crop rotations, and conservation tillage techniques build active, living soil.
By combining amendments, the benefits of guano can be maximized as part of a complete soil fertility regime. This is especially helpful when transitioning to sustainable farming methods and rebuilding deficient soils.
Safety Precautions When Using Guano
Fresh guano may contain live pathogens including E. coli, salmonella, histoplasma capsulatum fungus, and parasites. For agricultural use, certified guano is always processed to eliminate pathogens through heat drying, composting, and/or application of sodium carbonate. This makes properly sourced guano safe to handle. Nonetheless, observing basic precautions is recommended:
– Wear a dust mask, gloves, and eye protection when handling dry guano powder.
– Wash hands thoroughly after guano application whether by sprayer, spreader, or by hand.
– Allow around 30 days between spreading raw guano and harvesting crops.
– Keep guano from contacting edible plant parts like fruits or leaves.
– Store in sealed containers away from domestic animals.
– Rehydrate before applying to avoid wind drift of dry guano powder.
When basic guidelines are followed, commercial guano presents no significant health risks. Exercise common sense as you would when handling any agricultural products.
Environmental Considerations
Historically, seabird populations were severely threatened when guano was mined in an unchecked manner. Entire island colonies were decimated. Current regulations aim to prevent this by allowing only supervised surface harvesting. This scales guano production to sustainable levels that do not disrupt seabird habitats.
When used as a natural fertilizer itself, guano can benefit the environment versus synthetic alternatives:
– It improves soil health which enables reduced use of chemical fertilizers.
– Runoff is less likely, reducing potential impacts on nearby waterways.
– Regional sourcing reduces transport pollution and energy use.
– Nitrous oxide emissions are lower than conventional fertilizers.
– No fossil fuels are used in guano’s production.
With mindful stewardship, guano offers a way to add agricultural nutrients in sync with ecological balance. This helps sustain food production while also supporting healthy soils and diverse wildlife.
Conclusion
Guano refers to the nitrogen-rich dried excrement of seabirds that accumulates on islands where large colonies nest. This organic fertilizer was prized by ancient cultures and hugely popular in the 1800s before overexploitation nearly wiped out the resource. Today, strict management allows sustainable guano harvesting to continue on a smaller scale. When regulations and quality control practices are followed, guano provides a valuable renewable fertilizer and soil amendment for organic farmers and gardeners alike. It improves plant growth and yield while also enhancing overall soil and ecosystem health. With its unique history and ocean-sourced nutrition, guano fills an important niche as a time-tested, ecologically sound fertilizer option.