Bava Metzia 109 - Short-term vs. Long-term Leases

If one leases a field from his fellow for just a few years (less than seven), he may not sow it with flax and he has no rights to the beams of any sycamores (planetrees) growing there.

Although flax is a very profitable crop, it depletes the soil excessively, and it takes up to seven years for it to recover fully. Planting flax would lead him to return the land in worse condition than he received it.
This ruling applies only to a tenant-farmer, where the landowner receives a fixed payment no matter what the land produces. In the case of a sharecropper, we assume that the landowner agrees to a more intensive use of the land based on the principle "let the land become poor but not the owner".