(R. Eliezer to Rabbanan): (The Mishnah taught that if it's grain next to vegetables or vice-versa, according to the Rabbanan, one must distance it a Beis Rova. R. Eliezer said that for vegetables next to grain, it's six Tefachim.) Just as you are stringent in a square field to require a Beis Rova and nevertheless you are lenient for a row of vegetables to require only 6 Tefachim (Menachos 54(b)) - so too I am lenient in a square field (as I do not differentiate between a row and a square).

Question: Where do we find that the Rabbanan are lenient for a row and stringent for a square?

Answer (Baraisa): If one wishes to sow a row of vegetables in the middle of his grain field, he should make a row of separation 101/2 Amos long and 6 Tefachim wide.

(R. Yochanan): Only one type of vegetable may be planted (in order to distinguish it from the rest of the field).

(R. Zeira): R. Yochanan agrees that when the row is 7 Tefachim wide, he may plant a Tefach wide strip of one species on one side of it along the entire length and do the same with a different species along its other side. The middle 5 Tefachim combine with each of the Tefachs to make a separation row of 6 Tefachim.

Based on this teaching of R. Zeira, in Bavel they raised a question against R. Yochanan...

If he planted one half of the row with one species and now wishes to plant the other half with another species - Rav Chisda said that it is prohibited - he must uproot what he planted or fill in the rest of the row with the same species.

(R. Yudan): R. Chiya bar Ba and R. Shmuel bar Rav Yitzchak both disagreed with Rav Chisda, but they also disagreed with each other - one said that even if he planted three continuous Tefachim of the six (it's considered a row and he may plant there). The other said that if the three were not continuous - as there was one here, one there and one in the middle, it's considered a row. However, we don't know who said each opinion...

Conclusion of question: om that which R. Yosi/ R. Chiya citing R. Yochanan said that the permission applies only if there is no empty space (as the three Tefachim must be continuous), it must be R. Shmuel bar Rav Yitzchak who said that if the three that were planted were not continuous it's still considered a row...? (But we see that according to R. Yochanan, at least three Tefachim of the row's six Tefach width must be planted. This is unlike Rav Zeira (earlier in (e)) who said that according to R. Yochanan, one Tefach is enough.) (The Gemara doesn't resolve this.)

If the planted area on the sides is greater than the empty area, it is permitted.