Under the plough
Definition 1 of 2
Pro Tip 1/3Agricultural Setting
Use this phrase when discussing farming or crop cultivation. 
They put new land under the plough every year for maize.
Pro Tip 2/3Literal Use
The phrase is often used in its literal sense to talk about agriculture. 
The rich soil here has never been under the plough.
Pro Tip 3/3Active Farming
Describes land currently being worked on, not just any farmland. 
With half our fields under the plough, we're set for a busy season.