As soil temperatures rise in the spring and plants start putting on rapid growth, they call for more nutrients from the soil solution and the cation exchange capacity doles them out as needed. Warmer temperatures also stimulate the growth of a whole range of soil microbes, such as nitrogen-fixing bacteria. These little guys live on the roots of legumes—a class of plants that includes beans and peas. Now get this: You may remember from high school chemistry that nitrogen comprises four-fifths of the atmosphere and that a nitrogen molecule is N2, or two nitrogen atoms strongly linked together. Nitrogen-fixing bacteria have found a way to move an electron or two around and unhook the bond that holds the two nitrogen atoms together, like taking apart one of those metal Chinese puzzles. The free nitrogen atoms then combine with oxygen to form nitrates, and the nitrates feed the beans and peas. It’s a neat, symbiotic arrangement that costs the farmer or gardener nothing. If, however, you fertilize your soil with chemical nitrogen fertilizer manufactured in a factory, using costly fossil fuel (and lots of it), the soil becomes flooded with nitrogen, which turns off the nitrogen-fixing bacteria permanently. You end up destroying a free, natural system and replacing it with a costly, pollution-causing system for which you pay dearly. And yet, this kind of wasteful substitution of industrial chemicals for natural processes happens all the time on factory farms.

To put it simply, compost feeds plants what they need, in forms they like, at just the rate they require. And nature is just full of simple cycles and processes like these.