[Vanilla] Make Dispensers plant things

I'm not going to upload everything, but here's the commands I used for wheat seeds:

These commands need to be run only once:

/scoreboard objectives add isSeed dummy
/scoreboard objectives add isSeedPlant dummy

The rest of the commands all need to be on a 20t/s clock.

This command checks to see if the item is a wheat seed and if it wasn't dropped by a player:
/scoreboard players set @e[type=Item] isSeed 1 {Item:{id:minecraft:wheat_seeds},Age:0s,PickupDelay:0s}

This command checks to see if there's tilled soil under the seed, and if there is a dispenser next to the seed. This command needs to be duplicated 4 times, with the last set of tildes (~) changed to reflect the different cardinal directions:
/execute @e[score_isSeed_min=1,score_isSeed=1] ~ ~ ~ detect ~ ~-1 ~ farmland -1 execute @e[score_isSeed_min=1,score_isSeed=1] ~ ~ ~ detect ~1 ~ ~ dispenser -1 scoreboard players set @e[score_isSeed_min=1,score_isSeed=1,r=1] isSeedPlant 1

This command plants the seeds:
/execute @e[type=Item,score_isSeedPlant_min=1,score_isSeedPlant=1] ~ ~ ~ setblock ~ ~ ~ wheat

Finally, this command kills the seed item:
/kill @e[type=Item,score_isSeedPlant_min=1,score_isSeedPlant=1]