Commentary for Bava Metzia 9:2
הַמְקַבֵּל שָׂדֶה מֵחֲבֵרוֹ, וְהִיא בֵית הַשְּׁלָחִין אוֹ בֵית הָאִילָן, יָבַשׁ הַמַּעְיָן וְנִקְצַץ הָאִילָן, אֵינוֹ מְנַכֶּה לוֹ מִן חֲכוֹרוֹ. אִם אָמַר לוֹ חֲכֹר לִי שְׂדֵה בֵית הַשְּׁלָחִין זֶה אוֹ שְׂדֵה בֵית הָאִילָן זֶה, יָבַשׁ הַמַּעְיָן וְנִקְצַץ הָאִילָן, מְנַכֶּה לוֹ מִן חֲכוֹרוֹ:
If one received a field from his neighbor, and it were beth hashlachin [dry land, lacking sufficient rain (and, therefore, irrigated)] or a tree-field, [and "beloved" of the tenant-farmer by virtue of the tree, being enabled to share in the fruits without exertion] — If the well [from which the field were irrigated] dried up, or the tree were cut, this does not reduce his rental [if he received the field on rental, so many and so many korin a year; for in the beginning he did not indicate that he was adding to the rental because of the well or the field.] If he (the renter) said to him (the owner): Rent me this beth hashlachin field, or this tree-field — If the well dried up or the tree were cut, his rental is reduced, [the renter having indicated that he was adding to the rental because of the well].
Bartenura on Mishnah Bava Metzia
English Explanation of Mishnah Bava Metzia
But if he had said, “Lease me this irrigated field, or this field with trees”, and the spring dried up or the trees were cut down, he may give less than the prescribed rental.
In the scenario in this mishnah a sharecropper receives a field from the owner, and the field contains either a spring (an irrigated field) or it has some trees in it. Evidently the sharecropper will be growing grain in the field, but as an added bonus it has a spring, from which he can more easily water the field, or trees from which he may eat. After he makes his agreement with the owner, the spring dries up or the trees are cut down (assumedly by someone either than owner or the sharecropper). If the sharecropper had not explicitly stated that he was renting the field since it had on it a spring or some trees, he must still give the owner of the field the same amount of grain that was stated in the original agreement. Although the sharecropper will have to work harder to water the field (if the field had a spring) or he will lose the added benefit of the trees (if it was a field with trees), since he did not specifically stipulate that he was renting the field on account of the spring or the trees, the agreement is not effected. If, however, he specifically stipulated that he was renting a field with a spring or trees, he may reduce his payments if the spring dries up or the trees are cut down.