Chocobo Digging
From HorizonXI Wiki
Chocobo Digging is a hobby in FFXI in which adventurers use Gysahl Greens to get chocobos to dig up items. The only requirement to dig is to be riding a chocobo and to have greens in your invenotory. To dig, the player can use either the dig command from the menu options or /dig. Each time dig is used, one gysahl green will be removed from your inventory.
On Horizon there is a 100 item per real life day limit on how many items can be dug up. This limit increased by 10 for each rank-up achieved. The limit refreshes at Japanese Midnight. The message log will show a skill-up message when these are achieved.