Francesc Bonàs and Josep C. Honrat
Fundació Caixa d’Estalvis, Badalona, Spain
Seabird and bat guano manures are excellent ecologic fertilizers because their high content in phosphorus, nitrates, and other inorganic salts. However, their suitability as home fertilizers is limited by their remote source, which is confined to distant oceanic islands and deep caves. Domestic animal species are good providers of guano-like excrements, not only in the countryside farming activities (cattle manure), but also at home (pet guano) and at the daily street-life of our towns (dog shit). However, comprehensive studies on the attributes as soil nutrient supplements of this dung are scarce. Here, we have compared the properties as plant fertilizers of guano and guano-like excrements from a wide variety of domestic organisms, from non-pedigree dogs to silkworms. Human defecations were included in the study as a comparison. Faeces were carefully picked in situ by voluntary donors and collecting fellows, and were classified according to their species of origin. To allow normalization of the data and to avoid odour interferences, an automated shit processing protocol was performed under aseptic conditions. Samples were compacted using a modified French press, followed by slow-drying and a final step of vigorous grinding with a shitty beater. Tests were performed using hot chili pepper (Capsicum annuum) as a model for growth of Solanaceae plants, which constitute a plant family of major agricultural importance at home gardens world-wide. A summary of our study is graphically shown below, and detailed information will be provided elsewhere:
Our results illustrate the potential utility of guano from domestic animals as a reliable, cheap and environmentally clean biological fertilizer. Among the samples tested, Goldfish guano displayed the less attractive features as a domestic fertilizer, due to its elevated water content and difficulties in its obtaining. Conversely, stray dog shit stood out for its high fertilizing power and availability, with a low-cost supply. A survey of the manure market reveals that dog shit can compete in price and quality with artificial, non-renewable chemical fertilizers.