Strawberry Picking

Hillel from Neve Ya’acov asks:

I recently visited a sh’mittah-observant farm and
saw plenty of luscious strawberries growing on the ground. Since they were hefker
(ownerless), I wished to take a sackful home with me. However, one of the
farmers told me that it is forbidden to take such a large amount. Is this true?
If it is, why is it forbidden?

The Torah forbids the owner of a field to harvest the kedushas
crop growing in his field in the usual way (see Vayikro
25:5). It is rabbinically forbidden for any other person to harvest the crop in
the usual manner. Two types of change should be made in the harvesting process
in order to avoid any prohibition. Firstly, the amount collected should be less
than usual. Only a small amount may be gathered for each person. Some say that
this is only what can be eaten at three meals (see Sefer Hash’mittah,
Chapter 3, Note 12). However, if one is gathering food for a large group of
people, one may gather this quantity for each of them. If one is
collecting strawberries for a yeshiva, seminary or other institution which
provides food for hundreds of people, it could well be that filling a sack is
permitted! Indeed, as long as he does not harvest the entire field (which would
violate a Torah prohibition – see Chazon Ish, Shvi’is
12:6), there would seem to be no limit on the amount he can collect on the basis
of three meals per person. The second change required is in the method of
harvesting. One should use a tool which is different from that which is
generally used for harvesting this type of crop. If this is not possible, one
may use the normal method (Chazon Ish, 12:4-5).