Kilayim, Chapter Two, Mishnah 9. This mishnah deals with a person who has a field and wishes to sow different species in it. The question is how many different species may be introduced into a single field. We will also see that when plants are sown in a square plot, even if there is no large gap separating them, it may be permitted to sow them side by side, because they appear separate and distinct. It is worth noting that in the Mishnayos this mishnah is accompanied by several different diagrams, and we will address that below.
The text of the mishnah:
"Ha'rotzeh la'asos sadehu k'rachos k'rachos mi'kol min" - a person who wishes to make his field into k'rachos k'rachos, patch after patch. The literal meaning of 'karachas' is a bald spot, but here it refers to a bald spot that is destined to be sown - a square patch in which different species are sown.
"Oseh esrim v'arba k'rachos l'beis se'ah" - for every beis se'ah of field he may plant twenty four different patches, different places within it.
"Mi'karachas l'beis rova" - each patch is the size of a quarter kav. Since there are twenty four quarter kavs in a beis se'ah, one divides the beis se'ah into twenty four parts, and in each patch he plants a quarter kav. This is the measure used as a patch for planting a species different from the one beside it.
"V'zorea b'sochah kol min she'yirtzeh" - within that patch he may sow any species he wishes.
Patches of mustard:
The mishnah continues: "Eizeh karachas? Achas o shtayim - zor'an chardal" - According to the Talmudic note here, if within a wheat field there are only one or two patches, one may sow mustard in them, and it does not appear as kilayim, because mustard is always sown in a minimum of at least three patches. But "Shalosh - lo yizra chardal, mipnei she'hi nireis k'sdeh chardal" - with three patches it looks like a mustard field mixed into a grain field.
This ruling applies specifically to mustard. With other species sown in patches within a grain field, even three patches do not look like a field, since to be considered a field of those species it would have to be much larger and include many more patches.
The dispute between Rabbi Meir and the Sages:
Everything stated until now - that one may sow twenty four beds within a beis se'ah - is the opinion of Rabbi Meir. The Sages disagree and hold that within a beis se'ah one may sow only nine beds, and these are permitted, but ten are already forbidden.
How the patches are arranged:
Exactly how these patches are positioned is a matter of dispute among the commentators: is an empty patch required between each patch and the next, or may they be arranged so that they are adjacent to one another diagonally, according to some opinions. One should look at the diagrams in the Mishnayos to see the various opinions, since it is difficult to describe this in a recording.
The opinion of Rabbi Eliezer ben Yaakov:
Rabbi Eliezer ben Yaakov holds that even if the entire field is thirty times the size of what we have been discussing until now, one may not sow in it more than a single patch, that is, more than one species, and nothing further.
In summary: In this mishnah we learned how a field is divided into 'k'rachos' - square patches, in each of which a different species is sown: according to Rabbi Meir, twenty four patches in a beis se'ah, each the size of a beis rova, and according to the Sages, only nine beds. We addressed the law of mustard, where one or two patches are permitted and three are forbidden because they look like a mustard field, unlike the other species; the dispute among the commentators about how the patches are arranged; and the opinion of Rabbi Eliezer ben Yaakov, that one may not sow more than one species in a field.