A sackful of sand won't help the soil here much, but a dump truck full would.
(figuratively) A large number or amount (of something).
1853, uncredited translators, German Popular Tales and Household Stories: Collected by the Brothers Grimm, New York: C.S. Francis, Volume I, 74. “The Fox and the Cat,” p. 381,
[…] I understand a hundred arts, and have, moreover, a sackful of cunning!
1986, Hanif Kureishi, “Bradford” in Granta 20, Winter, 1986, p. 163,
He received sackfuls of hate mail and few letters of support.