"Bat guano has been used for centuries as an organic fertilizer to enrich our soil and help improve the quality of our crops."
https://greener4life.com/blog/bat-guano-as-fertilizer
"Guano has long been known as a valuable fertilizer. The weathered bird excrement provides your plants with an ideal mix of nutrients. However, obtaining guano is not always environmentally friendly."
"Guano is an organic fertilizer. This means that the nutrients mentioned above are not present in their pure chemical form, but are incorporated into natural mixtures of substances. In the soil, the nutrients must first be made available to the plants. This task is performed by the numerous microorganisms in the soil. They decompose the guano fertilizer and, among other things, form valuable humus.
Guano therefore acts as a slow-release fertilizer. When it is decomposed by soil organisms, it gradually releases nutrients. This makes guano very productive."
https://gardeninguru.com/guano-fertilizer-features-application-and-disadvantages/
"Plants love guano. It was an important agricultural fertilizer in the 19th century.
Not just any bird poop will do. Unfortunately a pigeon's gift to your car is not an effective fertilizer. Instead, bird guano usually refers to the desiccated droppings of seabirds. Thanks to the fish diet of these birds, their guano is a highly effective fertilizer."
https://americanhistory.si.edu/blog/what-load-guano-5-facts-you-didnt-know-about-bird-poop
"the use of seabird guano to fertilize crops. Guano—‘white gold’ as it came to be called—thus sustained agricultural intensification, supporting a substantial population in an otherwise extreme environment"
https://www.nature.com/articles/s41477-020-00835-4