Is it permissible to pay money as Zakah of wheat or barley instead of them?

A 2: Zakah on wheat and barley must be paid of their kind unless the owner sells the land along with its produce before the time of harvest and after the crops have ripened. In such case, he should pay one twentieth as Zakah from the value he was paid if the land was watered artificially (irrigated), or one tenth if it was watered naturally.