Tosefta do Pea 5:3

[With respect to] one who beats down his field until the poor people no longer come inside it, if his potential loss is greater than the poor's (see Y. Peah V.3.4, following Guggenheimer tr.), it is permitted, and if the loss of the poor is greater than his, it is forbidden. Rabbi Yehudah says, either way, he collects [the part of the poor] and deposits it on top of the [stone] fence, and the poor person comes and takes what is his.