Adam Clarke on Leviticus 27:16

Some part of a field - Though the preceding words are not in the text, yet it is generally allowed they should be supplied here, as it was not lawful for a man to vow his whole estate, and thus make his family beggars, in order to enrich the Lord's sanctuary: this God would not permit. The rabbins teach that the land or field, whether good or bad, was valued at forty-eight shekels, for all the years of the jubilee, provided the field was large enough to sow a homer of barley. The חמר chomer was different from the עמר omer: the latter held about three quarts, the former, seventy-five gallons three pints; See the note on Exo 16:16. Some suppose that the land was rated, not at fifty shekels for the whole of the years of the jubilee, for this would be but about 3s. per annum; but that it was rated according to its produce, fifty shekels for every homer of barley it produced.