A fence has a leniency and a stringency...

How is this? If there is an area smaller than a Beis Rova that is empty inside a grain field, one may not plant another species there. But if he surrounded that area with a fence, it is permitted.

If that area is a Beis Rova size, one may plant two species there (one on each edge). But if he surrounded the entire area with a fence, it would be prohibited.

Question: Does a fence that had seeds sown on its top and upper sides save the seeds (that it would still serve as a separation to permit sowing seeds on one side of it that are different to those that are on its other side)?

Answer #1 (R. Shmuel citing R. Zeira): (Tosefta) One is permitted to sow near dried out tree roots that are 10 Tefachim tall (as they serve as a separation). The Tosefta only permitted dried out roots, but moist roots would be prohibited. (So too here, the fence cannot act as a separation.)

Answer #2 (R. Yosi): (Our Mishnah taught that) one may plant them close to fallow land, plowed land, a stone fence, a (4 Tefach-wide) path, a 10 Tefach high fence. This shows that a sown fence can save the seeds (as it can act as a separation).

Rebuttal: Perhaps the Mishnah only applies when the fence is not sown, but when it's sown it does not save.

Question (R. Yudan): Can a dry area and irrigated land combine?

What's the case? If there was an irrigated area of 101/2 Amos by 6 Tefachim that does not require a dry area. If he made a strip of dry land on one side, may he plant other species next to the two sides of it? (The Gemara leaves this question unanswered.)

(Baraisa) (R. Yonasan ben Yosi): If there was a rock there 10 Tefachim long and 4 Tefachim wide (but less than 10 Tefachim high), it is permitted to plant two different species close to each side of it.

If it was 10 by 10 Tefachim, it is permitted to plant on all four sides.