Kilayim 2:1-2

Kilayim 2:1

If a seah of seed (about 13 liters) contains a quarter-kav of another species of seed (about half a liter), its proportion must be reduced before it can be sown. Rabbi Yosi says that he must remove the other species of seed completely, but if it was less than a quarter-kav, he may plant it, whether it was of one other kind or two. Rabbi Shimon says that one must reduce the quarter-kav only if it is made up of one other species; the Sages say any other species that combine to a quarter-kav.

Kilayim 2:2

This quarter-kav must be reduced when it’s one type of grain mixed with another, one type of bean mixed with another, or grain and bean mixed with one another. Vegetable seeds that are sown but not eaten combine as kilayim for one-twenty-fourth of a beis seah (a piece of land of 2,500 square cubits, which is typically fit to sow a seah). Rabbi Shimon says that this rule applies both stringently – i.e., to render it kilayim – and also leniently – such as when flax seed falls into grain. (Since more than a seah of flax seed can be sown in a beis seah, 1/24 of that would be larger than a quarter-kav. Therefore, a quarter kav of flax seed would not be kilayim.)