Master of Orion II: Battle at Antares/Feeding your people

All races except Lithovores need food:
 * A small shortage will make a planet's population stop growing.
 * A severe shortage will cause a population decline.
 * Natives are the most vulnerable to starvation, and start dying if their planet has even a slight shortage. Since you can't make Natives and Natives are at least twice as good at farming as the best farming race you can design, this is a severe loss.

For non-Lithovores, improving farmers' productivity is one of the most important early-game objectives, as it helps you to grow your population and / or move a few people from farming to research. Inefficient farming can indirectly lose you a game, because (except for extreme blitzers) you need to increase your research fast in order to win.

Even Lithovores need to think about food, because if they're successful they will usually conquer some planets with non-Lithovore populations.

Food production for each type of planet
This table shows food production per farmer with no bonuses, penalties or farming technologies. Of course there has to be a separate row for Aquatics, which have their own rules.

Zero-tech
On a recently-conquered colony, some of the population will be angry and unproductive, indicated by yellow icons. If you see yellow farmers, replace them with assimilated people.

If you are Feudal or Dictatorship (or their advanced versions, Confederation or Imperium) and the colony has no Marine Barracks, build one. The increase in morale will increase productivity by 25% of the base value in the table. Marine Barracks is a starting tech (no research required), so even Uncreative races can always use this.

Researchable technologies
Most of these technologies have alternatives at their levels of the tech tree, so non-Creatives have to make choices.

Note: the only purely agricultural tech Lithovores can research is Weather Controller - the rest don't appear on their Research Menus. Increases any planet's food production by 2, even on a Toxic / Radiated / Barren planet. For non-Creatives the alternative tech at this level is Biospheres (+2 population capacity), which most players prefer. Hydroponic Farm has 1 advantage: it is not affected by blockades (see below).
 * Hydroponic Farm (80 RP; 60 PP; maintenance 2 BC)

For non-Creatives the alternative tech at this level is Cloning Centers (+0.1 population growth per turn); that's a tough choice.
 * Soil Enrichment (400 RP; 120 PP; no maintenance)

Increases any planet's food production by 4, even on a Toxic / Radiated / Barren planet. For non-Creatives the alternative tech at this level is Weather Controller (see below), which most players prefer. Subterranean Farms have 1 advantage: they are not affected by blockades (see below).
 * Subterranean Farms (1500 RP; 150 PP; maintenance 4 BC)

Increases farmer's output by 2 food each (so not usable on no-farming planets). For non-Creatives the alternative tech at this level is Subterranean Farms (see above), but most prefer Weather Controller. Increases the output of a colony's farmers, workers and scientists by one per head. It's an expensive building. But it's the only tech at its level of the tech tree, so is always available to Uncreatives (the game designers probably included it to make sure Uncreatives get some sort of productivity boost in each occupation). And because it boosts all types of productivity, it's available to Lithovores.
 * Weather Controller (1500 RP; 200 PP; maintenance 3 BC)
 * Astro University (2000 RP; 200 PP; maintenance 4 BC)

An achievement that increases food production by 1 per farmer, even on Toxic / Radiated / Barren planets. For non-Creatives the alternative techs at this level are Gaia Transformation and Evolutionary Mutation. But this is at the very top of the Biology tech tree, and few competitive games get this far.
 * Biomorphic Fungi (7500 RP; 0 PP; no maintenance)

Transferring food between colonies
If you're farming, it's almost inevitable that some colonies will have a food surplus (especially if they have Natives). No-farming planets have a food shortage unless populated only by by Lithovores and / or Androids (manufactured population, not a type of race). And new non-Lithovore colonies usually have a food shortage because it's more important for them to start building something (often Housing in the early game).

You can use Freighters to transfer food instantly between planets. Freighters are built in fleets of 5 (50 PP; 0.5 BC per turn per individual Freighter that is actually in transit; must be researched; available to all races as they're in a "general" level at the start of the tech tree), but they can operate individually, and each can carry 1 unit of food. You need Freighters to transfer food to a colony even if another one in the same system has a surplus.

Blockade and its effects
Even the puniest warship can blockade a system that has no warships defending it. The effects of blockade continue until the blockader is destroyed, chased away or gets bored: Note: if 2 empires have colonies in a system, it's unclear whether both are affected by a blockade if the blockading empire is at war with only 1 of them.
 * Farming and industrial productivity is halved on all your colonies in that system (but not research).
 * Movements of your freighters within, to and from the system are impossible.

Blockades often cause food shortages - in the worst case one of your "breadbasket" colonies is blockaded and you get food shortages there and at the colonies that depend on its food exports.

Natives (if you have any) are the first to die of starvation - a serious permanent loss, since they are far better farmers than any race you can design.