In 1.13, the crop growth on the sand receives updates from the surrounding squares, for example the piston protrudes and retracts 16 times within the 0gametick to allow the cactus to grow 1 grid. 1.14 placing sand on a boat on a campfire will enable forced ripening, with 1 bar per 20redstonetick growth. In 1.15, Mojang "fixed" 0T falling sand in 1.14, but you can still use 0T ripening in 1.13. Snapshot 20W12A of 1.16 fixes this feature incorrectly, and we hope Mojang can be modified back.

From many Redstone Survival Players in China