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In the southeastern United States (U.S.), the impact of nitrogen (N) fertilizer rates on blackberry (Rubus L. subgenus Rubus Watson) yield, growth, and fruit quality have not been evaluated. In 2022 and 2023, 6 N rates (0, 30, 60, 90, 120, 150 lb N/ ac) were applied via fertigation for 15 weeks to one-year-old Ouachita blackberries in Clarksville, Ark. Plant tissue nutrient samples of primocane and floricane petioles and leaves were collected in alternate weeks throughout the growing season. From late May through early July, fruit harvest was conducted twice a week, and fruit quality parameters were assessed. Floricane yield and fruit quality were not affected by N fertilization rates, except fruit decay after seven days. Nitrogen fertilization rate x sampling date interaction was significant for primocane petiole NO3-N concentration, where higher N fertilization rates generally had higher petiole NO3-N concentration than lower rates at several sampling dates. Floricane petiole NO3-N concentration was not impacted by fertilizer-N rate. However, floricane leaf-N concentration was affected, and the 0 lb N/ac rate had the lowest leaf-N concentration but was not significantly different from other treatments except the 120 and 150 lb N/ac rates. Our first-year observations agree with previous research findings that blackberry primocanes are impacted more immediately by in-season N application compared to floricanes. Our second-year observations concur with existing literature that we would see differences in the N concentration of floricane tissue after a previous year's application of differing rates of N fertilizer. This trial will be continued through 2024 to study the impact of N rate on yield, fruit quality, leaf and petiole nutrient concentration, and cane characteristics in perennial blackberry production to identify a recommended N fertilization rate and the associated leaf- and petiole-N sufficiency ranges for blackberry in Arkansas. [ABSTRACT FROM AUTHOR]

In the southeastern United States (U.S.) the impact of nitrogen (N) fertilizer rates on blackberry (Rubus L. subgenus Rubus Watson) yield, growth, and fruit quality have not been evaluated. In 2022, 6 N rates (0, 30, 60, 90, 120, 150 lb N/ac) were applied via fertigation for 15 weeks to one-year-old 'Ouachita' blackberries in Clarksville, Ark. Plant tissue nutrient samples of primocane and floricane petioles and leaves were collected in alternate weeks throughout the growing season. From late May through early July, fruit harvest was conducted twice a week and fruit quality parameters were assessed. Floricane yield and fruit quality were not affected by N fertilization rates. Nitrogen fertilization rate x sampling date interaction was significant for primocane petiole NO3-N concentration, where higher N fertilization rates generally had higher petiole NO3-N concentration than lower rates at several sampling dates. Floricane petiole NO3-N concentration was not impacted by fertilizer-N rate; however, floricane leaf-N concentration was affected, and the 0 lb N/ac rate had the lowest leaf-N concentration but was not significantly different from other treatments except the 120 lb N/ac rate. Our first-year observations agree with previous research findings that blackberry primocanes are impacted more immediately by in-season N application compared to floricanes. This trial will be continued through 2024 to study the impact of N rate on yield, leaf and petiole nutrient concentration, and cane characteristics in perennial blackberry production to identify a recommended N fertilization rate and the associated leaf- and petiole-N sufficiency ranges for blackberry in Arkansas. [ABSTRACT FROM AUTHOR]