פירוש על פאה 5:3

אין מגלגלין בטופח – a form of thin pulse, which we call in Arabic Gilabaan. But Maimonides explained that it is a kind of seed which we call it Kortmin, and it is likened to barley. And Rabbi Meir states that we don’t irrigate this species with other kinds of seeds, to reap them together, for the greening that was appropriate to fall from the other kinds of seeds would fall from this worst species and it is found to cause loss to the poor.

Introduction Our mishnah deals with the potential problem of watering a field with a water wheel.

וחכמים מתירים מפני שאפשר – that gleanings will fall from the rest of the seeds as from the irrigating engine. And the Halakha is according to the Sages. Another explanation: We don’t bring up water in a wheel from the well to water the field or to sprinkle it until the irrigating engine waters on it at the time when the poor come for the gleanings, because it causes loss to the poor. But the Sages permit it, since it is possible that they would estimate the loss of the poor in this and give the owner the family according to the estimation that they would estimate upon it, and for Rabbi Meir who stated that we don’t irrigate, we estimate for the owner of the house his loss and take it from the poor.

They should not [irrigate a field] with a water wheel, the words of Rabbi Meir. Rabbi Meir prohibits watering a field with a water wheel before the poor come and collect their gleanings because the water will cause the gleanings to be ruined.

The sages permit it, because it is still possible [for the poor to get their gleanings]. The other sages permit this because he can just pick up the gleanings and put them on the side and the poor can come and collect them from there. Furthermore, if he does end up ruining some of their gleanings, he can always compensate them for their losses.