You know, in days of old, farmers would always leave some of their crop for the "wee folk"!
They believed it brought them good fortune and ensured a healthy harvest every year. And if they forgot to leave a little something, the fairies would get angry and punish the farmers by ruining their crops!
Sure, sure... today we may have scientific names for such things, like nitrogen, and carbon and humic acid...
...call it what you like. All I know is even the smallest little creatures play a BIG role in all the gifts we take for granted.