Farmer's Almanac
The Basics
In the Resource Extraction tab at the bottom, you can find the Farm building and the farm tool. The farm tool is used to create fields for the farmers to work through the Farm building.
Nutrients and Fertility
The term "nutrients" refers to how rich the actual tile is (or can be), while "fertility" is related to the crops themselves. Using the farming tool to move over various tiles, you'll find a section displaying X%/Y% (X: current fertility level, Y: maximum fertility level). This is the actual tile fertility level (referred to as nutrients to make it distinct from the plant based fertility) which will play the largest role on growing most crops. Fertility is the actual expected output of a tile if a crop is planted on it in its current state. Fertility varies from crop to crop and can still be impacted afterwards by things such as pollution. The nutrient recovery rate is roughly 8% to 10% per day on normal difficulty. Tiles recover nutrients whenever there is nothing actively growing on the tile. Nothing else plays a role, as even setting the crop type to fallow is just a way to ensure nothing get planted but is otherwise identical to no field existing in the first place.
Growth time
Growth times are a convenient 5% or 10% of a full year, taking the evening into consideration (translating to 864 seconds/1.6 days and 1728 seconds/3.2 days, respectively at the current 32 days in a year). Berries, Flax, and Mushrooms grow at 5%, while all other crops grow at 10%.
Winter
There is no actual winter as we know it, instead most crops rapidly die (90% death within 20-30 seconds, the rest following shortly after) when exposed to freezing temperatures (0 Celsius). This has the upside that if you warm the farm above that point, you can continue to grow crops all year round. Exceptions are Flax, Berries, and Trees, which stop growing at 0 Celsius but do not ever actually die, just like their wild counterparts. However, it may be best to let the field rest and recover nutrients in winter depending on what you are growing and the fact that most heat sources tend to cause harmful pollution. Speaking of pollution...
Rocks, light, and pollution
Rocks and pollution both cause a direct reduction in fertility (not nutrients) ranging from 50% to 100% fertility loss at 100% rock/pollution level. It is unclear at this time if having both results in an additive or multiplicative effect on fertility, as we could not find a farming Whisker willing to "harm my precious crops like that." Notable exceptions are Flax, which only takes a 20% fertility hit at 100% rock level, and Trees, which only take 25% fertility hit at 100% pollution.
The only light source in this world comes from the sky as far as the plants are concerned, so campfires and other fire sources will *NOT* work as substitute light. All crops have a minimum light level to grow (usually 75%) but it is unclear at this time what effect going below that has on fertility, growing speed and nutrient recovery, if any.
More things to consider
Mushrooms
Mushrooms are special in several ways. For starters, they do not suffer from rockiness at all and do not need any nutrients (though interestingly they will use it up if you fertilize their tiles anyway). Cold and pollution works similar to the other crops. But the final point is the biggest difference: they cannot stand sunlight. The way sunlight works is that every tile exposed to an open sky has 100% sunlight and every tile away from it reduces it by roughly 1/8th. Meaning that you need to be at least 8 tiles away from it in a direct line in order to grow mushrooms without them suffering damage. A good use for that buffer space is putting down warehouses and Farm buildings for your future mushroom farm.
How many farms can a farm farmer farm, when a farmer farms farms?
So how much work can a farmer handle? In short: about 72 tiles for 2 workers of the Farmers Guild affiliation in 1 farm building for the following crops: Cotton, Wheat, Tea Leaves, and Peppers. And about 36 tiles for the following crops: Berries, Flax, Mushrooms, and Trees.
The reason for this is that the 72 tile crops take 10% of a year to grow while being fairly fast to fully process at 50 base seconds per tile. This includes plant, 2 harvest actions, and clearing of the leftover material. This number is also before factoring in bonuses to work speed such as Farmers Guild affiliated mice gaining a 50% bonus from their guild. The others can maintain about half for 2 different reasons that have a similar end result: Berries, Flax, and Mushrooms only take 5% of a year to grow while still taking 50 base seconds to harvest, so a farmer can only get half as much work done before the first plant is ready for another round of attention. Trees, meanwhile, require 34 rather than 14 seconds to do each of the (usually) 2 harvest actions per tile, bringing the total process time to 90 seconds. So they need almost twice as long to fully process a tile and thus farmers only get half as many tiles processed before the first one is ready for another round of attention.
Small field vs. traditional farming
Say you have made a nice 12 wide, 6 deep section to farm Cotton in. The simple thing would be to designate it as a field, select it as Cotton, and get to work, right? Wrong! Each field will move between stages as 1 entity to avoid cluttering the various tiles into a weird mass of various stages. This means tiles that have been harvested will not be planted until all tiles in the same plot are done. This results in up to 71 tiles waiting for the last to be harvested before any are planted again. To make matters worse, planting 72 tiles is a lot quicker than harvesting them so your farmers will idle during growing and be swamped during harvest time.
The better way to treat your sweet 12 wide, 6 deep section of prime farming ground is to split it into 4 portions of 3 wide, 6 deep (or any other subdivision you prefer). Your farmers will harvest and replant each section one at a time and get it growing again while they work on the other sections. Doing it this way will have 3/4th of the farmland growing while 1/4th is getting processed and will eliminate or minimize worker idle time after the first harvest round is done.
Fertilizer
Fertilizer is a product that can be made at the Sifting Tower from potash after it is mined from the ground in the same way you would mine metals such as copper or iron. The research to actually produce fertilizer is fairly late into the tech tree. Overpaying taxes to 175% is an often easier and currently the only infinite method of obtaining fertilizer as a reward from The Claws. Once a field has the fertilize toggle turned on, any staffed Farm within range will have their workers retrieve fertilizer and begin applying it to the field. The fertilizer itself is consumed 1 at a time whenever a worker finishes applying it to a tile. Each one will add 200 charges of 1% nutrients to a stockpile tracked invisibly in the farmhouse itself (saving the leftover for the next tile). Applying fertilizer will result in the worked tile immediately setting the current nutrients to 200% and raising the max nutrients by about 6% to 8% each time fertilizer is applied, up to a max of 100% (max nutrients refers to the amount a tile will recover to on its own). This is a great way to create reasonably fertile fields that will continue to be usable even without further use of fertilizer.
Dreaded beaches
Spooky WIP
The impact the rock toggle has on non-rock behavior
In the past, the toggle would unintentionally result in all tiles of a field being cleared of leftover plant matter before any of them would be planted, requiring the mice to visit each tile twice as often. This has since been patched out in patch 19 and the toggle is now safe to stay on.
Fallow fields
Setting fields to fallow ensures nothing gets planted after the next harvest. This can be useful to ensure that nutrients can recover, pollution can dissipate away, or rocks can be be fully removed. In effect, "fallow" is a command to treat the tile as non-farmland for a while, as the only time when tiles will not recover nutrients is when something is actively growing. Fully grown plants recover nutrients at the same rate as fallow and non-farmland.
