In agriculture, what do you call a section within an orchard?

Solution 1:

Cuartel is related to the English word quarter. One sense of one meaning of quarter is indeed barracks, but another is an area of a city (exemplified by Latin Quarter). Spanish has this meaning too:"Cuartel, subdivisión administrativa de algunas municipalidades de gran tamaño." according to Wikipedia.

This suggests using a simple section (as in your question) area or zone. These terms reflect the man-made or arbitrary boundary of the sub-orchard*, while a grove might be expected to be surrounded by open space, and a stand of trees would be obvious to an observer (like a stand of oaks in a beech wood). A stand of red delicious in an orchard of golden delicious would fit this sense -- for a few weeks of the year.

*Another term you could use if desperate

Solution 2:

You could use grove instead of an orchard section.

a small wood, orchard, or group of trees.

Source

Solution 3:

A section of trees within a larger, wooded area is called a 'stand' of trees.

This citation is the title of a technical paper about reforestation programs :

A stand of trees does not a forest make: Tree plantations and forest transitions