"What lightning can do with tremendous temperatures and pressures, an enzyme (nitrogenase) can do in normal conditions: **it is produced by bacteria associated with the roots of leguminous plants** (pulses, as well as some trees) **or that live freely in soil or in plants**. Bacteria attached to the roots of leguminous plants are responsible for most natural nitrogen fixation—that is, for the cleavage of non-reactive N2 and for the incorporation of nitrogen into ammonia (NH3), a highly reactive compound that is readily converted into soluble nitrates and can supply plants with their nitrogen needs in return for organic acids synthesized by the plants. "As a result, leguminous food crops, including soybeans, beans, peas, lentils, and peanuts, are able to provide (fix) their own nitrogen supply, as can such leguminous cover crops as alfalfa, clovers, and vetches. But no staple grains, no oil crops (except for soybeans and peanuts), and no tubers can do that. **The only way for them to benefit from the nitrogen-fixing abilities of legumes is to rotate them with alfalfa, clovers, or vetches, grow these nitrogen fixers for a few months, and then plow them under so the soils are replenished with reactive nitrogen to be picked up by the succeeding wheat, rice, or potatoes**." ([Location 1134](https://readwise.io/to_kindle?action=open&asin=B08SGC3TD3&location=1134)) --- **Tags** -- [[quotes]], [[nitrogen]], [[fertilisers]], [[ammonia]], **Source** -- [[202412030828 - B - How the World Really Works]]