Kilayim, Chapter 4, Mishnah 1. From here on the tractate turns to the laws of kilei hakerem - the kilayim connected with vineyards. As mentioned, kilei hakerem are more stringent in halachah than the kilayim of seeds that we have learned until now, because they are forbidden even in deriving benefit from them, and no use whatsoever may be taken from them. Our mishnah, along with several of the mishnayos that follow, deals with an area inside the vineyard that has been left bare and empty of vines: how large must it be for other seeds to be sown in it, and at what size is it no longer considered a separate area but part of the vineyard surrounding it.
The measurements of the karachas and the mecholah:
"Karachas hakerem" - a bare spot in the middle of the vineyard. The area required in order for it to be permitted to sow there: "Beis Shammai omrim" - twenty four amos that are clear of any vines; "u'Beis Hillel omrim" - sixteen amos are enough.
"Mecholas hakerem" - according to most opinions this is the empty space between the vineyard and the fence, that is, at the edge of the vineyard and not in its middle. Here the required measurement is smaller: "Beis Shammai omrim shesh esrei amah" - instead of the twenty four amos they required for karachas hakerem; "u'Beis Hillel omrim shteim esrei amah".
"Ve'eizu hi karachas hakerem?"
The mishnah comes to define what that bare spot is, and states: "Kerem shecharav me'emtza'o" - a vineyard that was destroyed in its middle. From here the law divides (and we will explain it according to the opinion of Beis Hillel, who require only sixteen amos): "Im ein sham shesh esrei amah - lo yavi zera lesham" - one may not bring any seed there at all. But "hayu sham shesh esrei amah - nosein lo avodaso vezorea es hamosar" - one does not sow all sixteen amos; rather, one first gives the vineyard its "avodah": the area needed for working the vineyard in the normal way, which is four amos, so that animals can be brought in there to plow - and the rest may be sown.
In the case of karachas hakerem, where the vineyard stands on both sides of it, four amos of avodas hakerem must be given on each side. Therefore, out of the sixteen amos only eight amos remain available for sowing other kinds of seeds in that area.
The reasons behind the measurements:
The reason Beis Hillel require sixteen amos: besides the avodas hakerem - the four amos adjacent to every vineyard, which are essential and in which one may not sow at all - another four amos are needed, which are considered the measurement of a field, that is, a significant and substantial area. These four amos are needed on each side of the vineyard, so that the place will be considered a separate and significant area and not part of the vineyard. For if the area is less than four amos, each side is nullified and secondary to the vineyard, and is therefore considered part of it.
Beis Shammai, however, said that twenty four amos are needed, because in their view any area smaller than eight amos is nullified and secondary to the vineyard. Therefore sixteen amos are needed in the middle, plus four amos on each side for the avodas hakerem - twenty four amos in all.
In summary: This mishnah opened the laws of kilei hakerem, which are more stringent than the kilayim of seeds in that even deriving benefit from them is forbidden. We learned the measurements of "karachas hakerem" (Beis Shammai - twenty four amos, Beis Hillel - sixteen) and the measurements of "mecholas hakerem" (Beis Shammai - sixteen, Beis Hillel - twelve), the definition of the karachas - "kerem shecharav me'emtza'o", and the ruling that the vineyard is given four amos of its avodah on each side and the rest is sown. We also examined the reasons behind the measurements: the need for a significant area that is not nullified and secondary to the vineyard - four amos according to Beis Hillel and eight amos according to Beis Shammai. In the mishnayos that follow we will continue to delve into these measurements.