Mishnayos Kilayim Perek 7 Mishnah 3

The following are forbidden, but they do not prohibit [the seed sown there]:The remainder of a [legally inadequate] empty patch (karahat) of a vineyard. The remainder of a [legally inadequate] mehol of a vineyard. The remainder of a [legally inadequate] aris-gap. The [ground under the] remainder of papyrus-ropes [of a trellis]. But [the ground] beneath a vine, and within the place left to work a vine, and the [ground within] four cubits of a vineyard, these do prohibit the [seed sown there].