I've made a Sugar Cane farm on a multiplayer server, but I've noticed that the speed it grows is a bit slow and it is a large time consumer. I wanted to know if I can make this grow faster by placing a different ground block, like dirt vs. sand.
The block below the sugarcane doesn't affect it's growth rate
Xisuma made a video on this (along with a couple of other tests) a while back:
The sugarcane test starts at 3:12. He uses block update detectors to harvest the sugarcane the exact moment it grows and links the BUD to a dropper placing items in a chest as a counter. The test involves dirt, grass, sand, podzol, red sand and coarse dirt. The sugar cane is placed with MCEdit, making sure there's no head start. After one hour of testing with an increased
randomTickSpeed, all soils yield pretty much the same amount of sugarcane.
I can't seem to recall where I found this, so don't quote me on this just yet, but it has been stated that the block that sugarcane is placed on has no effect on it's growth (I'll do some more research when I get home). There is a possibility that the biome may have an effect, but that's just speculation (I highly doubt it though).
However, according to the wiki what can affect it's growing time is the moment when a sugarcane is harvested.
For example, sugarcane grows one block every X ticks (let's say 600, which is equal to 30 seconds). When a block is harvested, that time will reset. So if you harvested a block just after it grew, not much time is lost in it's growth. However if you harvested it just before it grew, you would have to wait an extra 600 ticks before it re-grew.