When launching the game I'm taken to the mod loading error screen.

It states:

"Kelp Fertilizer (kelpfertilizer) encountered an error during the complete event phase
java.lang.ArrayIndexOutOfBoundsException: -1"

Crash TXT File: kelpmodcrash.txt

Thanks for submitting the bug report and using the mod! This has been fixed in version 1.3 of the mod.

https://www.curseforge.com/minecraft/mc-mods/kelp-fertilizer