AutoFarmer

Automatic Farmer automatically plants wheat, carrots, potatoes or beets in nearby empty farmland. It can also automatically harvest nearby (ripe) instances of the same..

Enable it by pressing L for PLant menu (can be changed in Minecraft's controls screen). If you have seeds/carrots/potatoes/beets in your item bar, when you approach farmland they will be planted, replacing items you just harvested if you are in harvest mode. The mod will not harvest without immediately replanting (to prevent griefing)

Requires Fabric. Install Fabric Launcher, then put the Auto Farmer .jar and the Fabric API .jar file in your .minecraft/mods folder (create the folder if it doesn't exist)