If someone leases a field and the produce is eaten by locust or is windblown by the wind if it is a Makas Medinah (the damage was very widespread) and he may subtract from his lease.
R. Yehudah says if most of the valley was affected it is considered a Makas Medinah, while Ula says if the four fields on the four sides of the field were affected it is a Makas Medinah.
It is a Safek according to Ula if a different type of produce was growing in the four fields around the field and they were not windblown and the next four fields were wind blown if it is a Makas Medinah. (1)
If his field was windblown and the other fields were afflicted with a different disease or vice versa it is a Safek if it is considered a Makas Medinah.
If the owner instructed the person leasing the field to grow wheat and he grew barley and his field along with most of the valley was windblown he may not subtract from the lease payment even though it is a Makas Medinah because the owner can say if you would have grown wheat my prayers would have been answered and your crops would have been saved. (2)
If all of the owner's fields were windblown along with the leased field but most of the valley was not windblown he may not subtract from the lease payment because the owner can claim if the field was windblown because of my poor Mazal I would have been left with something.
If the leased field was windblown along with most of the valley and all of the fields of the person leasing the field were also windblown he may not subtract from the lease payments because it is his bad Mazal that caused the field to be windblown. (3)
If someone sells a field he may not redeem it within two years and if one of those years all fields are windblown or diseased or there is a widespread famine or it is a Shvi'is it doesn't count towards the two years.
Shmuel says if the fields were windblown from a Makas Medinah he may subtract from the lease payment only if he planted and the crops were windblown but if he didn't plant at all he must pay in full. (4)
If a shepherd abandons his flock and goes to town and a lion or wolf kill some of the flock we estimate if the shepherd would have been able to save the flock if he had not left and if so he is obligated to pay.
If the lease holder planted and the crops were windblown he must plant another time and if it is again windblown if it is a Makas Medinah and he may subtract from the lease payment and he is not obligated to plant again according to Rebbe who holds two times is a Chazakah.
According to R. Shimon Ben Gamliel who holds three times is a Chazakah he must plant a third time and if the third time it is also windblown he may subtract from the lease payment.
If the lease holder planted and it didn't sprout he must continue to plant until Adar and if by Adar the seeds were still not taking root if it is a Makas Medinah and he may subtract from the lease payments.
R. Yehudah says if the lease holder pays his lease with money even if the crops are ruined because of a Makas Medinah he may not subtract from the lease payments.
If someone leases a field for ten Kor of wheat per year whether and the field produces inferior or superior wheat he pays his lease from the wheat of this field.
If someone leases a field and it produces grapes and he makes swine and the wine turns into vinegar he may not pay his lease payment from the wine. (5)
If the grapes turned wormy between the harvest and the pressing of the grapes or the grain was put out to dry in the sun and it went bad he may pay his lease from the grapes or grain which were ruined.
If someone leases a field on condition to plant barley he may not plant wheat if it was on condition to plant wheat he may plant barley, while R. Shimon Ben Gamliel holds it is forbidden to plant barley. (6)
Money that was collected for Purim must be used for Purim and a poor person may not buy a shoelace with the money without an a condition being made in front of the people of the city according to R. Meir, while R. Shimon Ben Gamliel argues.
A BIT MORE
1. It is also a Safek if wheat and barley are considered two different types of produce.
2. The owner prayed that his wheat crop will be saved and since he grew a crop of barley his prayers were not answered.
3. Even though most of the valley was windblown he can't say that it is a Makas Medinah because all of his own fields were also windblown and he can't say that if it was my bad Mazal I would have been left with something because if he would have been left with something he would have been left with something from his own fields.
4. Even though most of the valley were windblown if he didn't plant he can't say that it is a Makas Medinah and even if he would have planted the produce would have been windblown because the owner could claim that if he would have planted his field would have been saved because of his merits.
5. Since the field produced good grapes and it was only after he made it into wine that it was ruined he may not pay from the wine.
6. Wheat weakens land more than barley and therefore according to the Tana Kama even though he made up to plant wheat he may plant barley, however R. Shimon Ben Gamliel holds that even though barley is easier on the field a person may not breach an agreement that he made.
ABANDONING THE FLOCK
If a shepherd abandons his flock and goes to town and a lion or wolf kill animals from the flock we estimate if he would have been able to save the animal if he had been there and if so he is obligated to pay. But if he could not have saved the animal he is Patur and the owner can't claim that if he had not abandoned the flock a miracle would have occurred and he would have saved the animal because the shepherd could claim that if he was deserving of a miracle he would have been Zocheh to the miracle of a R. Chanina Ben Dosa and the animal would have fended off the lions with their horns. The Ben Yehoyada asks how could the owner claim that a miracle would have occurred because if he was deserving of a miracle the lion would not have invaded the flock in the first place. The Ben Yehoyada answers that even a person deserving of a miracle if a miracle occurs it is subtracted from his merits unless a Kidush Hashem results from the miracle. If the lion would not have invaded the flock in the first place no Kidush Hashem would have resulted but if the shepherd saved the lions from the animals it would have been a Kidush Hashem.
If someone leases or rents a field from his friend if the crops are eaten by locust or are windblown if it occurred to most of the fields of the city he may subtract from his payments in accordance with the amount he lost. However if it didn't occur to most of the fields he may not subtract from his payment even though all of the fields of the owner were windblown. If all of the fields of the renter or the lease holder are windblown even though most of the fields of the city were also windblown he may not subtract from his payment because the loss is attributed to the renter. (Shulchan Aruch CM 228:1)