Flying machine melon bone meal farm

A bone meal farm built on melons instead of moss, inspired by ilmango and built by Shulkercraft. A long farmland strip is planted with melon seeds and watered every few blocks, and a slime block flying machine drags six hopper minecarts along a line of iron bars over the top, picking the melons up as it passes. Those melons drop into six composters which turn them into bone meal, and hoppers carry it to two chests. A hopper clock loaded with 224 items times the flying machine's return trips. Swap the composters for hoppers and the same build becomes a melon farm, and pumpkins work in place of melons.

If the flying machine reaches the far side and does not come back, add a block behind the piston. That is engineerconagher5603's fix.
If the slime blocks will not push down, put the iron bars into the minecarts one at a time first and then place the slime. Kenrizo did that on 1.21.4.
Honey blocks do not work in place of slime here, the two do not stick to each other.
The video never says which way the flying machine travels, so work out the facing before you start. willcoomans9674 had to tear the whole thing down over it.
Expect the hopper minecarts to come loose off the iron bars during long sessions. Several builders report it, thecpt6265 and DopeIsotope among them, and nobody has posted a fix.
hunterxtreme3047 replaced the composters with hoppers and got a melon farm that is cheaper than the usual piston and observer designs.