Lightyear Frontier: Crops and Crop Rotation

Steam Community guide by Pesky.

Quick reference

tl;dr

Nitrogenic soil Phosphoric soil Potassic soil Nitrogenic crop Wheat, Chromaize, Zappertwig - High Mutation Phosphoric crop Rabbage, Lumbloom, Colvine ? Mutation - High Potassic crop Polyberry, Caroot, Honeybottle High Mutation -

"I need this crop. What soil do I use ?"

Crops Soil for High Yield Soil for Mutation Wheat, Chromaize, Zappertwig Phosphoric Potassic Rabbage, Lumbloom, Colvine ? Potassic Nitrogenic Polyberry, Caroot, Honeybottle Nitrogenic Phosphoric

"I have this soil. What should I plant ?"

Soil Crop for High Yield Crop for Mutation Nitrogenic Polyberry, Caroot, Honeybottle Rabbage, Lumbloom, [Colvine] Phosphoric Wheat, Chromaize, Zappertwig Polyberry, Caroot, Honeybottle Potassic Rabbage, Lumbloom, Colvine ? Wheat, Chromaize, Zappertwig

Soils

The game features three types of soil. If you make new mounds in a particular biome, you expose a certain type of soil.
The type of soil gives it a slightly different colour. You might be able to see it only if you have side-by-side examples to compare. Far easier to hold the mouse cursor over the mound.
Biome Type Tint Outset Grasslands Nitrogenic Green Frostpeak Ridge Phosphoric Red Hexagon Valley Potassic Purple

Crops

Here are the things that need a mound to grow in. There are other plants that grow, but they must be planted directly into the ground, not into a crop mound.
After you have harvested a crop, it leaves traces of itself on the soil, changing the soil to be the same type as that crop. So if you have a Nitrogenic soil mount, and you want it to be Potassic, plant any Potassic crop in it, wait for that crop to grow to maturity and harvest it. The traces of crop which are left after the harvest will change the soil to be Potassic.
By figuring out a cycle you can work out a system where you get some sort of bonus for every crop you plant..
Nitrogenic Phosphoric Potassic Wheat Rabbage Polyberry Chromaize Lumbloom Caroot Zappertwig [Colvine] Honeybottle

What soil does to crops

[Various comments pointed out that I had these sections swapped. I have corrected them. Thanks everyone.]
In real life, correct crop rotation leads to more vigorous crops. You get more in the harvest, the crop grows bigger, or it is more resistant to disease. In the game this is presented as double yield on harvest.
Phosphoric soil & Nitrogenic seed --> High Yield
Potassic soil & Phosphoric seed --> High Yield
Nitrogenic soil & Potassic seed --> High Yield
The game adds a twist: do it exactly wrong (swap the soil and the seed) and you get a useful mutation. This does not happen in real life !
Nitrogenic soil & Phosphoric seed --> Mutated Yield
Phosphoric soil & Potassic seed --> Mutated Yield
Potassic soil & Nitrogenic seed --> Mutated Yield

Crop uses

If you have trouble seeing whether a crop has grown to maturity, step out of your mech and go look at it close up as a farmer. Mature crops have tiny white specs sparkling around them. But when you look at them as a person, not a mech, they always have a 'Harvest' prompt showing. It's easier to see than the tiny white specs.
As well as being essential ingredients for many recipes, crop oils can be used to keep your mech working and to sell to the merchant.
**** Chemistry Days to mature Oil Fuel bars Oil Value Plant / Wheat Nitrogenic 1 1 $5 Polyberry Potassic 3 2 $40 Caroot Potassic 4 3 $50 Rabbage Phosphoric 3 3 $60 Chromaize Nitrogenic 4 4 $85 Zappertwig Nitrogenic 4 4 $85 Honeybottle Potassic 4 5 $40 Lumbloom Phosphoric 5 5 $95 Colvine ?? ? ? $?