How do I leave a field fallow or under cover crop for a season?

With one click, for that season only, so your rest years are part of the plan instead of a note in your head. On the Farm Map, open Growing locations and click the green check next to the block: it switches off for the season you are viewing.

The block stays on your maps, greyed out on the Farm Map and with (Disabled) after its name on the Crop Map. Its beds leave that season’s growing space. Other seasons keep it active; click the check again to bring it back.

See Edit, move or remove a location.