Any se’ah in which there is a quarter[-kav] of a different kind, he must reduce. R’ Yose says: He must remove. [This applies] whether it is of one kind and whether it is of two kinds. R’ Shimon says: They spoke only of one kind. But the Sages say: Whatever is kilayim with the se’ah can be added together [to constitute] a quarter[-kav].

With what are these things said? Grain in grain, legume in legume, grain in legume, legume in grain. In truth, they said: Garden seeds which are not eaten combine to one twenty-fourth of what is sown in a beis se’ah. R’ Shimon says: Just as they said to be stringent, so did they say to be lenient. Flax in grain combines to one twenty-fourth of what is sown in a beis se’ah.

[If] his field was planted with wheat, and he reconsidered [and decided] to plant it with barley — he waits for it until it germinates, he turns [the soil], and afterwards he can plant. If it sprouted, he cannot say: ‘‘I will plant and afterwards turn [the soil]’’; rather, he must turn [it] and afterwards plant. How much must he plow? Like the furrows of the rain. Abba Shaul says: So that there will not remain a quarter[-kav] per beis se’ah.

[If] it was sown and he decided to plant it, he cannot say: ‘‘I will plant and afterwards turn [the soil]’’; rather, he must turn [it] and afterwards plant. [If] it was planted and he decided to sow it, he cannot say: ‘‘I will sow and afterwards uproot’’; rather, he must uproot and afterwards sow. If he wants, he can raze till less than a handbreadth, sow, and afterwards uproot.