Public Service Announcement: On account of Klei rolling back most of the nutrient changes, this guide is once again up to date. Mostly, anyway. Durian changes have stuck, so it's not +4, -8, +4. The table will be changed in a few hours to reflect this, but I've replaced all the old Durian combinations with new ones. And I'll soon be updating with even more combinations.
Guess who had a ton of free time on his hands and decided to compile a list the possible combinations of 2-3 crops that require a grand total of zero nutrients to grow, meaning you only need to take care of tending and watering.
Note, the combinations listed here must exist within each individual soil tile for this to work; crops in one tile cannot feed crops in an adjacent tile.
But first, have a free table of farm plant stats as of the latest patch. (The wiki's page had not been properly updated when this was made, so I had to make my own table to figure things out.)
Now, on to the possible configurations of a self-feeding farm...
Type A: Three Different Crops in Equal Amounts
This is by far the most common configuration. I couldn't come up with a way to get all the crops to meet the family requirement, so I went with a simple columns design instead. Turn out that, aside from 2 crops at each corner, which were "isolated", the rest had no issue growing into oversized plants. It is possible that long term use of this design will cause a bit of a nutrient imbalance at these 4 corner tiles, but I believe the difference in growth speed (nutrients are consumed/produced when going from one stage to the next) between the isolated plants and the rest is small enough that this will not happen.
In any case, this imperfection is more than acceptable for me, because it does not scale with farm size. If you were to make, say, a 10x10 farm area, you could grow 10x10x9=900 plants in it and only 8 of those would be "isolated". So the imperfection becomes largely insignificant in bigger farms.
Type B: Two Crops in Equal Amounts
For this one, you can place 4 of each crop in every tile, for a total of 8 crops per tile. To ensure the family requirement is met, I've arranged crops of the same type in an L shape, which is contained entirely within one tile. This means you can minimize or expand this setup as much as you want, because each tile is effectively autonomous. It also means you can combine multiple self-feeding farms of this type without a need to pay attention to plant proximity.
Type C: Two Crops at a 2:1 Ratio
Last but not least. Here each tile has 2 adjacent columns of the first plant (which is always either Toma Root or Watermelon) and 1 column of the second plant (in this case, Dragon Fruit). The first plant's family requirement is met within the tile itself, so you need not concern yourself with. However, you must make sure that the second plant is always facing another of its kind.
As a result, the minimum size of this setup is 1x2 and you must take care to ensure that the crops are always facing other crops of their kinds for this to work. (e.g. Toma Roots facing Toma Roots, Dragon Fruits facing Dragon Fruits)
And now, the part you've all been waiting for: all the possible crop combinations, arranged by preferred season. (Preferred season halves growth time and you need plants to grow at roughly the same ratio, or it will result in a nutritional imbalance.)
AUTUMN:
- Carrot/Corn/Potato
- Carrot/Corn/Eggplant
- Pumpkin/Corn/Potato
- Pumpkin/Corn/Eggplant
- Toma Root/Potato
- Toma Root/Eggplant
- Toma Root/Toma Root/Pepper
- Garlic/Pepper/Onion
WINTER:
- Carrot/Potato/Asparagus
- Pumpkin/Potato/Asparagus
- ... that's it
SPRING:
- Carrot/Corn/Potato
- Carrot/Corn/Eggplant
- Carrot/Potato/Asparagus
- Carrot/Eggplant/Asparagus
- Carrot/Watermelon
- Toma Root/Potato
- Toma Root/Eggplant
- Toma Root/Toma Root/Dragon Fruit
- Watermelon/Watermelon/Onion
- Watermelon/Watermelon/Pomegranate
- Dragon Fruit/Garlic/Onion
- Dragon Fruit/Garlic/Pomegranate
- Onion/Durian/Dragon Fruit
- Pomegranate/Durian/Dragon Fruit
SUMMER:
- Garlic/Pepper/Onion
- Garlic/Pepper/Pomegranate
- Garlic/Dragon Fruit/Onion
- Garlic/Dragon Fruit/Pomegranate
- Toma Root/Toma Root/Dragon Fruit
- Toma Root/Toma Root/Pepper
- Watermelon/Watermelon/Onion
- Watermelon/Watermelon/Pomegranate
That's all, folks!