The fields at your base are perfect for a bit of post-apocalyptic gardening. After tilling the soil and giving your seeds a good watering, all it takes is waiting a few days before the fruits (or veggies) of your labor are ready for harvest. It's up to you whether you want to sell them, use them in a recipe, or find some other use for them entirely.
Crops give better benefits when they're cooked rather than eating them straight after harvesting. Once you unlock the skill for the recipe you want to try, all that's left is a trip to the nearest fire pit or kitchen and you can get cooking.
Be sure to keep watering your seeds if you want them to grow. Sludge is fine to use on your crops, but agua cola will make them grow even faster.