Related su Kil'ayim 2:16

ועל הכלאים – We announce that they should reduce the other seed until there should not remain in it one-quarter of a Kab for a Seah, as is taught in Chapter Two [Mishnah One] of Mishnah Kilayim: that every Seah that has one-quarter of a Kab from another species should reduce it, and our Rabbis explained that after the seeds have ground, even one in one-thousand one must uproot everything, for every two kinds and every one kind singly is permitted, but they forbade through mixtures – but relinquishment does not belong witht his, for specifically, when they estimate after that which has been combined at the time of seeding, there is no need other than to reduce, for according to the Torah, one in two is cancelled out, but they don’t call seeding “mixed seeds” other than because of merely appearance’s sake , one must reduce, but after they grew, there is no need for renunciation, but one must uproot everything so that nothing would remain other than one of the species.