One of the best organic fertilizers out there – at least in terms of how plants respond to it — is bat guano. As most of you probably already know, bat guano is made of bat droppings. What you probably don’t realize is that bat droppings need to be aged for a while in an arid environment before they become guano. Caves provide the perfect environment for this to occur, and so that is where most bat guano comes from.
Because guano needs to be aged in special surroundings before it is used it is not a rapidly renewable resource. Instead it’s kind of like peat in that it takes anywhere between decades and thousands of years for the raw material from which it is made to develop into the stuff that we use. Furthermore, by harvesting bat guano we can actually damage the ecosystems present in the caves from which the bat guano is harvested. Think about it – bats generally feed outside the cave, so when they defecate inside the cave they are actually bringing new nutrients into the cave – nutrients that other creatures can use. Whole ecosystems are based on this poo! So when we harvest bat guano from a cave what we are doing is disturbing a specialized ecosystem – a very unique system.
So am I encouraging you away from bat guano? No more than I would encourage you to consider reducing your usage of peat – or of oil — or any other non-renewable resource. I can’t deny that it’s a great fertilizer, but if you want to use an organic fertilizer why not at least consider one that is renewable instead of one that is from a limited resource and which may cause harm to a unique ecological system?