Status of crop fertility management and plant tissue nutrient concentration of blackberry in the southeastern United States

The blackberry (Rubus subgenus Rubus Watson) industry in southeastern USA has expanded rapidly over the last 20 years. Surveys of the predominant cultural practices surrounding fertility management and current nutrient status of blackberry crops could inform the development of blackberry fertility management recommendations specific to the region. An online survey was distributed in 2021 to evaluate the most used crop fertility management practices by blackberry growers in the Southeast, including: use of irrigation, method of fertilizer application, soil testing, and fertilizer rates. Among the 30 growers who completed the questionnaire, ‘Natchez’ (53%) and ‘Ouachita’ (53%) were the most common cultivars. Slightly acid soils (mean pH 6.1) predominate the region. The use of some type of weed barrier (18% plastic mulch, 16% landscape fabric) or weed barrier with herbicide (32%) is quite common. Mean annual fertility rates were slightly below the current recommended rate of 67-90 kg ha^‑1 (60-80 lbs acre^‑1) of N annually for established plantings, and fertilizer application method varied (banded (39%), broadcast (22%), fertigation (22%), or some combination of these). Most growers (73%) do not use leaf sampling to monitor crop nutrient status. In addition, a regionwide survey of blackberry tissue nutrient status was conducted in July and August 2021. Most recently mature leaves (MRML) of primocanes were collected from multiple cultivars in Alabama, Arkansas, and Mississippi. A total of 77 samples were collected and analyzed for nutrients. Mean plant tissue concentration for P (0.20%), K (1.25%), Ca (0.74%), Mg (0.38%), and B (32 ppm) fell within currently recommended leaf tissue nutrient ranges for blackberry sampled postharvest. However, values for N (2.44%) were slightly below the current recommended ranges for the Southeast. More extensive leaf tissue nutrient sampling across the region is ongoing to verify the nutrient status of southeastern blackberry.