הלכה על קידושין 77:8

To not sow seeds of forbidden mixtures and not graft in any place in the Land: To not sow two species of seed, such as wheat and barley or fava beans and peas, together - only in the Land of Israel - as it is stated (Leviticus 19:19), "your field shall you not sow [with] a forbidden mixture." And the explanation comes about it (Kiddushin 39a) that the verse is speaking about a field that we have in the Land.