Current literature on blackberries indicates that inadequate nitrogen (N) fertilizer application negatively impacts plant growth and profitability for blackberry growers. Overapplication of fertilizer can decrease fruit marketability and increase labor costs, while insufficient fertilization stunts plant growth and decreases yield. The current N fertilizer rate recommendation for southeastern blackberry (67–101 kg N/ha) was developed outside the Southeast. The objectives of this study were to verify the current blackberry N fertilizer rate recommendation for the Southeast by investigating the effect of N fertilizer rate on ‘Ouachita’ blackberry yield and plant growth. Tissue culture plug plants of ‘Ouachita’ were planted in 2021, and fertilized with ammonium-nitrate from 2022 to 2024 at six different rates (0, 34, 67, 101, 134, 168 kg N/ha) at the University of Arkansas Fruit Research Station in Clarksville, AR. Fertilizer was applied via drip irrigation over fifteen weeks starting at primocane emergence. The experiment was laid out in a randomized complete block design with five plants in each replicate (n=4). Each year marketable and non-marketable blackberry yield was recorded. Subsamples from plots were also collected to assess fruit firmness at the day of harvest and fruit quality after seven days (decay, leakage, and red drupelet reversion). In the spring (2023-2025) plants were pruned to a grower standard and pruning weights (kg) were collected. In this study, marketable yield ranged from 2.64–2.82 kg/plant per year. No significant differences in yield were observed across fertilizer rate or fertilizer rate by year interaction. Total yield and percent non-marketable fruit were not observed to be significantly different across N treatment. Percent fruit decay after seven days was highest at the 168 kg N/ha rate, which was significantly higher than the 0, 34, and 67 kg N/ha rates. Firmness at day of harvest, percent leakage and red drupelet reversion after seven days were not impacted by N rate. Higher rates of N fertilizer resulted in higher pruning weights (p
