Kilayim 3:2-3

Kilayim 3:2

Crops normally grown in large fields may not be planted in small plots of land but vegetables may. Mustard and small peas are examples of things that may not, while large peas may. If a border was originally a handbreadth high but it wore down, it is permitted because it was permitted when he planted there. A furrow or a dried-up water channel may be planted with three different species: one on each side plus one in the middle.

Kilayim 3:3

If the end of a row of vegetables extends into a field planted with a different species of vegetable, this is permitted because it is clear that it’s the end of the former. If a field is planted with one type of vegetable and the owner wants to plant a row of a different vegetable, Rabbi Yishmael says the intervening furrow must run the entire length of the field. Rabbi Akiva says it must be six handbreadths long by six handbreadths wide (about 18 inches on each side). Rabbi Yehuda says the furrow need only be as wide as the sole of one’s foot (i.e., a handbreadth, which is about three inches).