Tosefta do Pea 5:9

[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.

[If a poor worker] received [a one time job] to harvest a field, [then] his son cannot glean [the gifts to the poor right] after him [before other poor people will have a chance to glean that field]. Rebbi Yossi says, “His son may glean after him.” But sharecroppers, and [regular] tenants, and a person who sells his standing crops to his friend in order [that his friend should] harvest them, [in all of these cases] his (i.e. the sharecropper’s, or tenant’s, or friend’s) son can glean [the gifts to the poor right] after him [before other poor people will have a chance to glean that field]. If there were [in the field] poor people who are not fitting [to be allowed] to glean [the gifts to the poor, then] if the owner of the field can prevent them [from gleaning], he is allowed to do so, but if [he is] not [able to prevent them from gleaning, then] he should leave them alone [and let them glean anyway] because of peaceful relations [between people].

Rebbi Yehuda says, “A person who made his whole field into sheaves [in order to later] stook them [into stooks, which in turn will be taken to the final stack] is [considered to be] like someone who bundles [sheaves] in [order to put them in a] stack [of sheaves, which makes the sheaves inside the stooks eligible to become Shikcha (forgotten sheaves),] and [then] rounded it (i.e. the stack) out [as if he has completed the stack] and [then brought more sheaves and] pressed [them] into the stack [after the stack seemed to be already finished, which is still considered to be the final act of bundling, which makes these sheaves eligible to become Shikcha].” Bet Shammai and Bet Hillel agree that if [a person] proclaimed [his produce to be] ownerless [only] to people, but not to animals, [or only] to Jews, but not to Non-Jews, [it is still considered to be] ownerless [and anyone can come and take it].

Two gavels separated from one another are [considered to be] Shikcha (forgotten sheaves), [but] three [gavels] are not [considered to be] Shikcha. Two sheaves separated from one another are [considered to be] Shikcha (forgotten sheaves), [but] three [sheaves] are not [considered to be] Shikcha. Two grapevines separated from one another (i.e. from separate tree trunks) are [considered to be] Shikcha (forgotten sheaves), [but] three [grapevines] are not [considered to be] Shikcha. Two [grape] berries [lying next to each other on the ground] are [considered to be] Peret (individual fallen grapes), [but] three [grape berries lying next to each other on the ground] are not [considered to be] Peret. Two stalks [of grain] separated from one another in the usual fashion are [considered to be] Leket (fallen stalks), [but] three [stalks of grain] are not [considered to be] Leket. These are the words of Bet Hillel. Rebbi Yossi says, “Chananyah, the son of the brother of Rebbi Yehoshua says, ‘Any [type of produce] where the property of the poor person (i.e. some kind of gift to the poor) can come in the middle [of two sets of produce, one standing and one detached, both of which are one Seah in volume], for example grain and vineyard, does not combine [to form two Seahs and therefore both parts are still considered to be Shikcha]. However, any [produce] where the property of the poor person (i.e. some kind of gift to the poor) cannot come in the middle [of two sets of produce, one standing and one detached, both of which are one Seah in volume], for example fruits of a tree, does combine [to form two Seahs and therefore both parts are not considered to be Shikcha].’”