As crops are harvested, nutrients are taken away from the soil and handily put onto your plate. However, they must be replenished in the soil. In addition to plowing under nutrient-rich cover crops, we return all culled vegetables to the fields and also add natural minerals. We lime to raise the soil's pH balance, and rely on organic fertilizers to achieve the nutrient balance best for plant growth.
We also use liquid fish emulsion as a nitrogen source; we think of it as a vitamin booster shot, as plants are able to utilize it rapidly.