Nutritional Study of N.C. Blackberry Cultivars Brenda R. Cleveland, NCDA&CS Agronomic Division Objective Determine the sufficiency range for nutrient concentrations in well-fertilized, healthy blackberry plant tissue under North Carolina conditions Rationale Blackberries are grown on about 400 acres in North Carolina. The most common commercial cultivars — ‘Navaho’ and ‘Ouachita’ — have biennial shoots and perennial roots. Second-year shoots (floricanes) yield berries, and first-year shoots (primocanes) remain vegetative providing “food” for the next season’s berries. Nutrient sufficiency ranges used by NCDA&CS in interpreting tissue test results are based on data from old cultivars grown primarily in the 1970s. Sufficiency ranges are available for newer cultivars (Clark 1997), but they have not been verified under N.C. field conditions. For this reason, NCDA&CS and NCSU Cooperative Extension decided to establish a nutritional baseline study for these blackberries grown in N.C. Nutrient concentrations of mature primocane leaves collected after harvest and before dormancy are typically used to plan (predict) a fertilization program for the following season. Nutrient concentrations of tissue samples collected during early growth, at bloom and during fruit help diagnose current-season nutrient problems. Materials and Methods In 2008, tissue samples (most recently mature leaves) were collected from floricanes and primocanes of both cultivars at each of four growth stages: early (April), bloom (May), fruit (June–July) and mature (late July–September). Samples were collected from ten locations—research stations and commercial grower farms—across the state. Laboratory analyses measured total concentrations of 11 essential plant nutrients. Results Average macronutrient concentrations collected from mature primocanes were generally within Clark’s ranges (Table 1). Therefore, in 2009 NCDA&CS will adopt these ranges to better help growers manage nutrients and maximize yield when they use plant tissue analysis as part of their nutrient management program. Cane types of both cultivars showed similar trends over growth stages: concentrations of N, P, K and S decreased; Ca increased; and Mg remained about the same over the season. At all growth stages, primocanes had higher N, P and K and lower Ca levels than floricanes. Mg and S levels were similar in both. Reference Clark JR. 1997. Fertilizing blackberries: an overview. In: Proceedings of the North American Bramble Growers Association 12th annual meeting. Louisville (KY). p 55–7. N.C. Department of Agriculture and Consumer Services — Steve Troxler, Commissioner Agronomic Division Web site: www.ncagr.gov/agronomi/ June 2009 Table 1. Comparison of macronutrient averages: former and current NCDA&CS blackberry sufficiency ranges vs. baseline study values NCDA&CS Sufficiency Ranges 2008 Baseline for Mature Primocanes 2 Nutrient before JAN 09 after JAN 09 1 Navaho Quachita x N 3.0–4.0% 2.4–2.9% 2.90% 2.40% P 0.2–0.6% > 0.15% 0.18% 0.17% K 2.5–3.5% 1.0–2.0% 0.84% 0.77% Ca 0.5–1.0% > 0.5% 0.51% 0.68% Mg 0.2–0.4% > 0.3% 0.30% 0.38% S 0.2–0.6% > 0.13% 0.15% 0.15% x 1 Based on data from Clark (1997); 2 7 Navaho and 11 Ouachita samples