(R. Yehudah): If one finds a single rock with a lime mark on it, only underneath it is Tamei. If two rocks are marked with lime, then: if the space between them is also marked it is Tamei, if not, the space is Tahor.
Question: A Beraisa says that the space between two marked rocks is Tamei, even when the space itself is not marked (provided the space has not been plowed over, in which case it is Tahor).
Answer: The Beraisa is talking about a case where a bit of the lime goes beyond the rocks, into the intervening space. If a plow has been there, we may assume that the plow scraped some marking off the rock onto the adjacent space, but the space itself was never actually marked. If there was no plow, this possibility doesn't exist, so we must assume that the extra lime was put there purposely to indicate that the space is Tamei.
WHEN THE BOUNDARIES OF THE FIELD ARE MARKED
If one or two or three of the boundaries are marked, only that area (the boundary itself) is Tamei. If all four boundaries are marked, the entire enclosed area is Tamei (and the marked boundary itself is Tahor).
Question: The Mishnah said that Kil'ayim inspectors go out on Chol ha'Mo'ed Pesach. This contradicts a Mishnah elsewhere that the inspectors go out on 15 Adar.
Answer: They go out both times, in Adar for early crops and in Nisan for later crops (or in Adar for grain and in Nisan for vegetables).
(R. Yochanan): These times (15 Adar and Chol ha'Mo'ed Pesach) apply only when there is no known, obvious Kil'ayim growing, but if there is, the inspectors go out immediately, whenever it occurs.
Question: Why was Chol ha'Mo'ed chosen as the time for this activity?
Answer: Because labor is cheaper then.
Deduction: The wages for the inspectors must come for the Terumas ha'Lishkah, for if it would come out of the pocket of the individual farmer we would not be so concerned to choose a time when the price is cheaper.
Question: How much of the Kil'ayim has to be uprooted by the inspectors?
Answer: As the Mishnah (in Kil'ayim) says - until there is less than a quarter Kav of growth per Se'ah of crop (a ratio of 1:24).
Question: A Beraisa says that the WHOLE crop is expropriated.
Answer: That Beraisa was taught after a Takanah was made, which took this measure so that the farmer should not get free weeding service from the inspectors.
MISHNAH - TWO DISPUTES
(R. Eliezer ben Yakov): Water may be drawn from one tree to another (although it is not necessary to prevent loss [it is a Beis ha'Ba'al], it is permitted because it involves no exertion whatsoever - Rashi on Rif), but an entire orchard may not be done this way (too much exertion). The Chachamim disagree and permit the entire orchard.
(R. Eliezer ben Yakov): Seeds that were not watered at all before Chol ha'Mo'ed may not be watered on Chol ha'Mo'ed (they can easily wait). The Chachamim disagree and permit it.
GEMARA - DISCUSSION OF 4:b (according to most Rishonim, but not Rashi)
(R. Yehudah): If the seeds are in moist ground, it is as if they had been watered before Chol ha'Mo'ed and R. Eliezer ben Yakov permits watering during Chol ha'Mo'ed (because the seeds begin to germinate, and will spoil if not watered).
The Gemara brings a Beraisa (which contains the same exact two disputes as the Mishnah - Tosfos) that confirms R. Yehudah's statement.
Ravina concludes from this Beraisa that it is permitted to lightly water a garden on Chol ha'Mo'ed, even though it is not for preventing loss but for achieving a gain.
BERAISOS ABOUT WATERING
Problem: One Beraisa says light watering is permitted (for a Beis ha'Ba'al) on Shemitah but not on Chol ha'Mo'ed Another Beraisa says it is permitted on both Shemitah and Chol ha'Mo'ed
Solution: The first Beraisa goes like R. Eliezer ben Yakov who forbids watering for profit, permitting it only to prevent loss. The second Beraisa is like the Chachamim, who permit watering for profit.
BERAISA ABOUT WATERING BEFORE SHEMITAH
Light watering is permitted (for a Beis ha'Ba'al) before Shemitah to enable growth during Shemitah.
Furthermore, this is permitted on Shemitah to enable growth after Shemitah. (But watering ON Shemitah FOR Shemitah is forbidden - Rashi).
MISHNAH - TWO TOPICS
One may trap moles and mice from a tree field (where they cause major damage) or from a wheat field (where they cause minor damage), in the normal manner, on Chol ha'Mo'ed and Shemitah. This is the opinion of the Tana Kama. Chachamim (or R. Yehudah) permit it for a tree field, but require a Shinui for a wheat field.
One may repair a broken fence on Chol ha'Mo'ed (but not build a new one). On Shemitah he may even build a new one.
GEMARA - EXPLANATION OF THE TERM ISHOS (MOLES)
BERAISA ABOUT DESTROYING PESTS
One may trap moles and mice, etc., as in Mishnah.
One may destroy anthills (on Chol ha'Mo'ed).
(Raban Shimon ben Gamliel): How is this done? Some dirt is brought from one anthill and placed into a different anthill.
(Abaye): This only works if the other anthill is on the other side of a river without any bridge over it (so that the dirt is completely unrecognizable to the new ants), and is more than a Parsah away.