Cut-and-come-again, or repeat harvesting, is a practice in which a single planting of greens is harvested on multiple occasions. This is a common practice among small-scale, urban, and home producers in which the outermost leaves are removed, leaving the growing center of the plant intact enabling multiple harvests without compromising plant health. As this practice is not common among large-scale and commercial producers, there are currently no research-based fertilizer recommendations for cut-and-come-again greens. General guidance simply suggests continued, nitrogen-heavy fertilizer applications to ensure repeated harvests. This type of guidance is not easy to follow for beginners or for growers looking to improve their cut-and-come-again yields. An experiment was designed to examine eight different fertilizer application strategies to determine which provided better growth and nutritional quality in later kale harvests while limiting nutrient leaching. Fertilizer applications for the cut-and-come-again treatments (CC) ranged from an initial fertilizer application matching local nutrient recommendations, to repeated applications either the initial complete application or a nitrogen side dressing at every third, every other, or at each harvest. A single harvest control (ODB) was also harvested at the baby stage at each CC harvest. At each harvest, total and marketable yield were measured and crop quality for marketability was assessed per the USDA guidelines for kale and greens. There were more issues with slow growth, slow regrowth, and missing harvests for pots in the fall than the spring, and more issues in 2023 than in 2022. Some issues were directly related to significant caterpillar damage in the fall of 2023 which also affected the marketability of the leaves harvested. The expected dose response to fertilizer treatment was not observed in any growing season of the two years of the study completed so far. While some differences in yield between treatments were observed, these were predominantly between the ODB control and CC treatments, but not among CC treatments. The expected drop in yield with successive harvests was also not consistently observed in CC treatments. The CC treatment receiving only the initial fertilizer application exhibited a drop in yield with successive harvests in only two of the four growing seasons. Further examination of the fate of nutrients in the leaf material, soil and leachate from the experiment should explain these unexpected results and provide more clarity on an optimal fertilizer treatment.
