Implied question: Any amount is called a field, like we say in Kidushin (61a) 'we know that an area in which one sows a Kor (30 Sa'im) of barley (i.e. 75,000 square Amos) is redeemed for 50 (Sela'im, at the beginning of Yovel). What is the source that the same rate applies to [an area in which one sows] a Se'ah, half-Se'ah, or quarter Se'ah? It says "Sadeh" (i.e. of any size).

Answer: Even so, it is not important to toil to plow and seed if it is less than (the area in which one sows) nine Kabim.

Implied question - Citation (Kesuvos 112a): A heretic said to R. Chanina "you properly praise your land. My father bequeathed to me a Beis (the area to seed a) Se'ah. I get from it oil, wine, grain, legumes... (This shows that even a Se'ah, i.e. six Kabim, is worth working!)

Answer: That was in a place where [the land] was blessed exceedingly.

Explanation #1 (Rashi): A Stam Achsadra has no walls at all.

Also, [Rashi's] text in Eruvin (94b) says "Shmuel does not hold that Pi Tikra (Yored v'Sosem, i.e. to consider the outer edge to descend to make a Mechitzah) in four [directions], but in three, he says so.

I.e. in an Achsadra, which has no walls at all, Shmuel does not hold that Pi Tikra (Yored v'Sosem for all four walls.

Therefore, Shmuel says that in an Achsadra in a valley, we carry only within four [Amos]. However, in three, he says. I.e. if there is one wall, in three [directions] he says Pi Tikra.

Explanation #2 (Ri): A Stam Achsadra has three walls, like it says below (25b) that the world resembles an Achsadra. The north side is not surrounded [by a wall].

In Eruvin (94b), the text says that [Shmuel] does not hold for three, but he holds for four;

I.e. when there are only three walls, we do not say Pi Tikra on the fourth side. However, for four walls, i.e. when there is somewhat of a wall also on the fourth side, he says Pi Tikra.

Also Achsadra d'Bei Rav has three full walls, and the fourth is four Amos tall. In Achsadra Romis, the fourth wall is only 10 Tefachim tall.

Alternatively, in Achsadra d'Bei Rav, the fourth is 10 tall, and in Achsadra Romis, it is less than 10 Tefachim.

Implied question: It says in Gitin (59b) that Rav Huna read [from the Torah first,] like a Kohen (even though he was not a Kohen), for Rav Huna was different, for even R. Ami and R. Asi, the esteemed Kohanim of Eretz Yisrael, were submissive to Rav Huna, and here he asked from [Rav Ami]!

Answer: R. Ami is not the same as Rav Ami.

Explanation (R. Chananel): He asks about a caravan that camped in one place, how they divide the manure.

Explanation #1 (Rashi): He wants to put walls around the four Amos that he has in the Mavuy around his opening.

Question (Ri): We do not find that he has four Amos in a Mavuy, only in a Chatzer!

Explanation #2 (Ri, R. Chananel): The case is, he is at the end of the Mavuy, by the closed side, and he wants to close opposite his opening the entire width of the Mavuy;

Now, Rav Huna says that the Bnei Mavuy can stop him, even though they are outside (his place), for he increases the Derech for them, i.e. traffic;

The Bnei Mavuy can say that when there are many in the Mavuy, they can enter until the end of the Mavuy;

Through his closure, he increases the Derech for us, through people who trample on us in the Mavuy, and they will even need to enter the Chatzeros, due to the great pressure.

Support #1: We find the expression "he increases the Derech for them" in this way. A Mishnah below (59b) says that if one bought a house in another Chatzer, he may not open it to a Chatzer of partners;

The Gemara (60a) explains that this is because he increases the Derech for them, i.e. traffic.

Support #2: The Tosefta in Bava Basra (1:4) says that if one has a store in Reshus ha'Rabim, and wants to open it to a Chatzer of partners, they can stop him, for he increases the Derech for them.

Explanation: [It uses] by itself, i.e. the last does not use with it;

"The outer one uses by itself" does not mean like this. Rather, it is by itself, i.e. it does not use with others.