From Lexicanum

A α-class (alpha class) or Agri-World (short for Agricultural World or Farming Planet) is one devoted to food production. The majority of its surface is given over to producing food for other worlds reliant on such imports - the food itself forms part of the planet's required tithe. Governors of such planets are required by the Adeptus Terra to protect the harvest and meet the quotas places on them. Often inter-commander rivalry leads to attempts to destroy or steal crops and livestock and then blaming them on pirates or raids¹.

One method of defining an agri-world is where at least 850 parts per 1000 of the planet's surface are covered by some form of crop cultivation, hydroponics, animal fodder or animal husbandry. The population usually ranges from between fifteen thousand to one million - which is widely spread across the planet. The tithe grade of such worlds range from Exactis Prima to Exactis Particular².

Notable Agri-Worlds

Planet name	Segmentum	Sector	Subsector	System	Population
Bellis XIV	Unknown	Unknown	Unknown	Unknown	Unknown
Chiros	Segmentum Pacificus	Unknown	Unknown	Unknown	Unknown
Hagia	Segmentum Pacificus	Sabbat Worlds	Unknown	Unknown	Unknown
Iax	Ultima Segmentum	Unknown	Unknown	Iax System	Unknown
Kabaal II	Unknown	Unknown	Unknown	Unknown	Unknown
Masali	Ultima Segmentum	Unknown	Unknown	Unknown	Unknown
Silvanos II	Unknown	Unknown	Unknown	Unknown	Unknown
Tarentus	Ultima Segmentum	Unknown	Unknown	Unknown	Unknown
Verdan III	Unknown	Unknown	Unknown	Unknown	Unknown
Quintarn	Ultima Segmentum	Unknown	Unknown	Unknown	Unknown

Masali, Quintarn and Tarentus form the group of planets called the 'Three Planets' in Ultramar, all of which are desert worlds. They are all classed as agri-worlds because of vast horticultural cities and moisture traps spread across the surface as well as bio-domes under which grow highly fertile forests. They are highly successful at producing vast amounts of food³.

Sources

• ¹:Warhammer 40,000: Rogue Trader p.134
• ²:Warhammer 40,000 3rd Edition Rulebook p.114
• ³:Codex: Ultramarines (2nd Edition) p.14

Worlds of the Galaxy

Imperium	Adeptus Astartes Homeworld • Agri World • Cardinal World • Civilised World • Dead World • Death World • Desert World • Feral World • Feudal World • Forge World • Hive World • Ice World • Industrial World • Jungle World • Knight World • Mining World • Ocean World • Paradise World • Penal World • Research Station • Shrine World
Xeno	Xenos World • Daemon World • Exodite World • Tomb World • Maiden World • Crone World • Ork World • Tau Empire • Craftworld