Of worms and microbes we are so thoughtlessly destroying
It was Charles Darwin who first realized the importance of worms. He kept an array of them in jars on his mantelpiece and found that they gradually process leaves and other debris through the acids in their stomachs and turn this detritus into soil. He also dissected their stomachs and almost invariably found tiny fragments of stone. They dissolve rocks and make their nutritious elements available to plants. In a process geologists call isostasy worms push soil downhill, and as an ice cube always rises to the surface in a glass of water, fresh rocks with their precious minerals rise to the surface to take the place of the topsoil the worms have moved. Thus, in natural processes that are achingly slow the nutritious powers in the soil are constantly renewed. But not only worms. Astonishingly, there are at least five billion microbes in a teaspoonful of soil, all with their part to play in making soil fertile. The major elements in soil fertility are nitrogen, phosphates and potassium, and of these by far the most important is nitrogen. When plants grow they use up these elements in the soil, but some plants, such as legumes, replenish it. Peas and beans, for example, take in nitrogen from the air and specialized bacteria transfer it from the nodules on the plants’ roots into the soil. This is why traditional farming practised crop rotation, interspersing crops like wheat and cabbages with legumes.