And whence is it derived that it is forbidden to benefit from vineyard kilayim? It is written here "kodesh" (i.e., "tikdash"), and elsewhere, "kodesh," (Vayikra 5:15 "and he sin unwittingly [by deriving benefit] from the holy tings ["kodshei"] of the L-rd.") Just as there, derivation of benefit is being forbidden, here, too, derivation of benefit is being forbidden.
"lest there be rejected the fullness of the seed … and the produce of the vineyard." When is the produce rejected? When it takes root. And grapes? When they become like the 'white (egyptian) bean'. "which you shall sow": This tells me only of what he himself sows. Whence do I derive (as likewise interdicted) what his neighbor sows (in the former's field) and which he would like to sustain? From "the seed" — in any event.