Don’t forget about the importance of letting a field lie fallow. This also kills off a lot of pests and diseases due to affected crops not growing.

Incidentally this is a system used for thousands of years and is mentioned in the Bible as a law for the Israelites whereby they were directed to leave a field to lie fallow every 7 years. Time between fallows doesn’t really matter but the principle has been there for a long time and it’s only now we know why.