Kilayim, Chapter Two, Mishnah One
Our mishnah deals with a seah (=6 kav) in which a quarter of a kav (1/24 of the seah) of at least one different species of seed has been mixed. If the other species is at least 1/24 of the main species, it is forbidden to plant this mixture. However, if there is less than 1/24 of the other seed, it is permitted to plant the mixture and this is not kilayim. In our mishnah we learn what the person can do to remedy a mixture of seeds that has more than 1/24 of the other species.
1) Any seah which contains a quarter [of a kav] of a different species, one should reduce [its proportion of the latter]
2) Rabbi Yose says: one should pick [it all out].
3) Whether it consists of one species or of two species.
4) Rabbi Shimon says: they said this only if it consists of one species.
5) But the sages say: anything which is kilayim, in a seah [it adds up] in making up the quarter.
Section one: According to the first opinion in the mishnah, if the other seed is more than 1/24 all he has to do is reduce the proportion, either by adding more of the dominant seed or reducing the minority seed.
Section two: Rabbi Yose is stricter and holds that he has to pick out all of the minority seed before he can plant. Since the mixture was originally prohibited, it is not sufficient to just adjust the proportion. However, Rabbi Yose agrees that if the mixture was originally less than 1/24 he can plant it without concern for kilayim.
Section three: The above rules apply whether or not there were one or two or more minority seeds. The first opinion still holds that he can adjust the proportion so that there are less than 1/24 of the minority seeds, and Rabbi Yose still holds that he must pick them all out.
Section four: Rabbi Shimon limits the leniency in section one to a case where there was only one minority species. If there were two different minority seeds, he must remove them all before he plants.
Section five: The sages add a new rule. If two species are kilayim with each other, such as barley and lentils, then when they are mixed in with a dominant seed such as wheat, the barley and lentils add up and if they are together more than 1/24 of the total amount, the mixture must either be reduced or the minority seeds removed. However, if the species are not kilayim with each other, such as barley and oats they do not add up, because oats is not kilayim with barley (see mishnah one).