The pasuk states (Devarim 22:9), "You shall not sow your vineyard with Kilayim" - this teaches that one is only liable for sowing two species. These are the words of R. Yashiya. R. Yonasan prohibits even with one species in a vineyard.

R. Yonasan's source is - the pasuk states (Vayikra 19:19), "You shall not sow your field with Kilayim", so why must the Torah add the pasuk of (Devarim 22:9), "You shall not sow your vineyard with Kilayim"? To be stringent even with one species.

R. Yashiya's source is the same question as was asked by R. Yonasan and the Chevraya answered that it teaches about the warning given to a person planting Kilayim in his vineyard - whether he was warned from the pasuk "your field" or he was warned from "your vineyard", he receives lashes.

Another explanation (R. Bun bar Chiya): To give different minimum separations - 'your field' refers to two types of seeds, where the separation must be 6 Tefachim (otherwise he transgresses); 'your vineyard' refers to planting another species near a vineyard, where 4 Amos is required (otherwise he transgresses).

What's the case? (R. Yochanan taught earlier (Menachos 29(f) - Perek 1 Halacha 9) that one does not transgress unless the two seeds were fenced in (or if he plants them in an area of 6 by 6 Tefachim in his grain field that is bare).) If there was a fence built inside the vineyard, it cancels the status of vineyard; if there was fence around the outside of the vineyard, that's a Mechol HaKerem (and 12 Amos outside of it may not be planted). Rather, it's the case of a field where there was produce that was removed in an area of 6 by 6 Tefachim.

This follows the statement of R. Chanina that something that is prohibited cannot form a partition to save.

It was suggested that it could, however, form the partition needed to prohibit (meaning to surround seeds, thereby causing them to be prohibited as Kilayim)...

Question: According to R. Yonasan, since the pasuk said, "Don't sow your field with Kilayim", but since it is prohibited to plant even one type of seeds in a vineyard, why did the pasuk need to say, "(Don't sow your vineyard with) Kilayim"?

Answer: It's like the statement of R. Hila, that when a pasuk says extra words, it is merely to give extra explanation, since this is the way of the Torah.

Alternatively, it's like the statement of R. Zeira - "Don't sow your vineyard with Kilayim" - if not for the word Kilayim, I might have thought that it's only prohibited to plant other seeds next to a pre-existing vineyard, but to sow all of the seeds together would be permitted.