Protein content — Kale

The protein level in kale depends directly on the nitrogen nutrition of the plants; therefore, the use of nitrogen fertilizers is a determining agrotechnical factor for the accumulation of protein compounds in the leaf mass. Protein content metrics in this crop often exceed those of other cruciferous vegetables.

In breeding practice, protein content is considered an important quality trait, though it rarely serves as the sole criterion for culling varieties. When selecting hybrids, agronomists typically favor a complex of traits, including yield, resistance to diseases such as clubroot, and the content of vitamins, antioxidants, and fiber.