פירוש על קידושין 77:14

R. Joseph now retracts his statement that outside of the Land one may plant mixed seeds. The basis for this retraction is the actions of Rav, a Babylonian amora, who seems to plant the garden of the rabbinic academy in rows in order to prevent the mixture of the seeds.

Abaye rejects R. Joseph’s reading of why Rav planted the garden in rows. If he had planted it in the way that gardens were to be planted in order to avoid the mixing of the seeds (four sides of a square, each with a different species and one row of another species in the middle), then we could be sure that he was doing so in order to avoid the problem of kilayim. But since this is not what Rav did, we can offer other assessments of his motivation. He might have done so either because this makes the garden look nicer or to save the attendant, the one harvesting the vegetables, the trouble of having to search for what he was looking for.