Once upon a time there was a peaceful corn farmer. After every harvest, he would plant clover to replenish the soil with nutrients. But how does the clover do this?

Once the clover has grown, the farmer lets his sheep graze in the fields. This allows the field to be fertilized by their nutrient-rich waste.

When the sheep eat the clover, the nitrogen in the plant proteins are incorporated into their tissues. When an animal emits waste or dies, fungi decompose the organic matter and release the nitrogen back into the soil.

The decomposition of organic matter produces ammonia (NH3).

Another way to produce ammonia is through nitrogen fixating rhizobia bacteria, which are hosted by legumes like clover. They take nitrogen from the air and fixate into a form plants can use!

The ammonia then undergoes nitrification and is transformed into nitrites and nitrates.