Bird droppings, also known as guano, have been used as fertilizer for centuries. Guano is rich in nitrogen, phosphorus, and potassium – three nutrients that are essential for plant growth. When bird droppings decompose, these nutrients are released into the soil, providing a natural fertilizer for plants. Some types of guano, especially seabird guano, contain even higher concentrations of nutrients than typical animal manures. This makes guano an excellent organic fertilizer option for farmers and gardeners looking to enrich their soil and boost plant growth.
What is guano?
Guano refers to the feces and urine of birds, bats, and seals. It often accumulates in large quantities in areas where bird and bat populations are high, such as caves or coastal islands. Guano comes from the Quechua word “wanu”, which means “dung”.
The composition of guano varies depending on the species’ diet. Seabirds that feed primarily on fish have guano that is exceptionally high in nitrogen. The guano of bats and cave-dwelling birds contains more phosphorus and potassium. In general, guano contains all three essential macro-nutrients that plants need – nitrogen, phosphorus, and potassium. It also provides smaller amounts of organic matter and trace nutrients like calcium, magnesium, and sulfur.
Types of guano
There are several types of guano used to create fertilizers:
- Seabird guano – From seabirds like cormorants, boobies, and pelicans. It has a high nitrogen content.
- Bat guano – From bats living in caves or ruins. It has balanced NPK levels.
- Cave bird guano – From birds like pigeons, nesting in caves. It has high phosphorus.
- Chicken guano – From poultry in coops. Lower in nutrients than wild bird guano.
Seabird guano is considered the highest quality fertilizer, with nitrogen levels from 8-12%. Bat guano and cave bird guano have more balanced NPK levels. Chicken guano is relatively lower in nutrients, but still useful.
History of Using Guano as Fertilizer
Guano has been used as a soil enricher since ancient times. Ancient civilizations, including the Romans, Chinese, and Incas collected deposits of bird and bat guano to use on crops.
The guano trade took off in the early 1800s, when large deposits were discovered on the Chincha Islands off the coast of Peru. It quickly became a highly valued export, providing nitrogen and phosphorus to fertilize fields in Europe and North America. By the mid-1800s, South American guano deposits were being rapidly depleted. New artificial fertilizers were developed to replace guano, but it remains in use today as an organic fertilizer option.
Benefits of guano fertilizer
Compared to synthetic fertilizers, guano provides these advantages:
- Natural organic matter – Improves soil texture and water retention.
- Slow release nutrients – Nutrients are released over time, reducing leaching.
- Microorganisms – Guano introduces beneficial bacteria and fungi to the soil.
- Trace elements – Provides calcium, magnesium, sulfur and more.
- Acidifier – Can help lower soil pH in alkaline soils.
Using guano enables organic crop production and environmentally sustainable farming.
Collecting Guano
Before guano can be processed into fertilizer, it first has to be collected. Guano is harvested from both wild sources and from captive bats and birds.
Wild Sources
In areas near large seabird colonies, bat caves, or cliffside bird habitats, guano accumulates naturally. Workers use scrapers and shovels to collect deposited guano without overly disturbing the birds. Care has to taken not to deplete the natural guano reserves too quickly.
In some cases, collectors simply wait for the guano to fall through mesh screens held below roosts. This is less disruptive to the birds.
Captive Sources
Guano can also be collected from captive bat and bird populations. Large bat houses and aviaries are set up to facilitate guano harvest. Wire screens collect the droppings below roosts and perches. This captive method provides a consistent guano supply without impacting wild populations. However, guano from wild, free-ranging birds has higher nutrient content from their more varied diets.
Processing
After collection, raw guano goes through a screening and drying process:
- Large debris is removed through screens.
- The guano is dried, either in the sun or using low-heat driers.
- It is filtered into different grades based on pellet size.
- Packaged for bulk transport and sale.
Proper drying and storage prevents guano from decomposing and losing nutrients. The end product is a dry, granular fertilizing material high in nitrogen, phosphorus, and other nutrients plants need.
Using Guano as Fertilizer
There are a few ways that guano can be applied:
Raw Guano
In its raw, unprocessed form, guano can simply be spread as a top dressing over soil. It slowly breaks down, releasing nutrients. This is an easy direct application method. However, raw guano needs to be reapplied frequently to maintain fertility. It can also release excess nitrogen too quickly when fresh.
Composted Guano
Mixing guano with yard waste, manure, straw, or other carbon materials during composting helps further break it down. After composting for several months, the end result is a stable, nutrient-rich organic fertilizer. Composted guano makes nitrogen more available for plant uptake.
Guano Teas
Steeping guano in water releases soluble nutrients, creating a liquid fertilizer tea. Guano teas provide immediate nutrient availability and are simple to strain and apply. But nutrients may leach out of the soil quickly using this method.
Pelletized Guano
Some companies pelletize guano into a form similar to chemical fertilizer pellets. This makes application more precise and nutrients more stable. Pelletized guano can be broadcast across lawns, fields, or gardens using a spreader. The pellets break down over time to fertilize soil.
Recommended Application Rates
When applying guano as fertilizer, use this general guide for application rates:
Use | Application Rate |
---|---|
Vegetable garden | 5 lbs per 100 sq ft |
Flower beds | 2 lbs per 100 sq ft |
Lawn top dressing | 10 lbs per 1000 sq ft |
Potted plants | 1 tbsp per gallon of soil |
Compost pile activator | 1 cup per cubic foot of compost |
These are general guidelines that may need to be adjusted based on your soil needs and the nitrogen content of the specific guano you are using. Always check the source to determine nutrient levels.
Finding Guano Fertilizer
While you can sometimes harvest guano yourself from wild sources, buying processed guano is often more practical. Here are some places to find it:
- Online retailers – Many specialty fertilizer stores sell guano online, often in bulk quantities.
- Farm supply stores – Some farm/ranch supply stores sell guano fertilizer along with conventional fertilizers.
- Organic garden stores – Check stores specializing in organic gardening methods and products.
- Specialty avian shops – Stores catering to bird owners may carry guano from captive sources.
When purchasing, look for guano that specifies its exact nutrient analysis to determine how much nitrogen, phosphorus, and potassium it contains. This helps determine optimal application rates.
Pros and Cons of Guano Fertilizer
Some key benefits and drawbacks of using guano as fertilizer:
Pros
- Natural organic nutrients
- Promotes healthy soil
- Environmentally sustainable
- Slow release nutrients reduce leaching
- Lower soil pH
- Adds beneficial microbes
Cons
- Limited supply and availability
- Strong odor
- Potential for excess nitrogen runoff
- Possible high mineral salt content
- Labor intensive collection process
When used correctly, guano’s advantages as an organic fertilizer source typically outweigh its disadvantages for many farmers and gardeners. But care should be taken to source it sustainably and apply it at proper rates.
Conclusion
Though often overlooked today, guano provided a critical source of fertility that fueled agriculture before synthetic fertilizers. Looking forward, guano remains a viable organic fertilizer option. It provides a natural way to add nitrogen, phosphorus, potassium and other nutrients to enrich soil. With care taken in how it is harvested and applied, guano can be an eco-friendly alternative to increase yields and support sustainable farming methods.