Research on nitrogen (N) allocation and accumulation in blackberries has primarily focused on floricane-fruiting varieties. However, there is a gap in existing literature on primocane-fruiting blackberry N allocation due to how relatively new primocane-fruiting blackberries are to the commercial industry. The objectives of this study were to investigate how fertilizer N is partitioned among plant parts in ‘Prime-Ark Traveler®’ and quantify the percent N recovery by the plant. In 2023, 15N labeled ammonium-nitrate was applied at a rate of 134.4 kg N/ha to a planting of ‘Prime-Ark Traveler®’ blackberries at the University of Arkansas Fruit Research Station in Clarksville, AR. Plants were fertilized via drip-irrigation over fifteen weeks. In 2023, plant biomass samples were collected in triplicate at four physiological stages: (1) small green floricane fruit, (2) peak-floricane harvest, (3) peak-primocane harvest, and (4) after floricane senescence. This paper focuses on results of leaf, cane, and crown 15N content. Due to senescence, floricanes were not collected at stage 4. Plant parts were separated by cane type before being dried and analyzed to determine mass fertilizer-N recovery (MFNR) and fertilizer recovery efficiency (FRE). MFNR represents the uptake of 15N fertilizer by individual plant organs (g/plant organ) at a given stage. FRE was calculated as a percent of 15N fertilizer in the plant (MFNR) out of total applied (g), with total FRE determined by averaging the FRE of plants at stage 4 and accounting for removed tissues such as fruit and floricanes. Primocane leaf MFNR was highest at stage 3 (1.84 g) and significantly different than stages 1 and 2. Physiological stage did not impact floricane leaf MFNR. Primocane cane MFNR was highest in at stage 3 (0.78 g) and was significantly different than stages 1 and 2. Floricane cane MFNR was highest at stage 1 (0.50 g) and was significantly different than all other stages. No significant differences were observed for MFNR in crowns across physiological stage. The finding that floricane 15N decreased over the season while primocane 15N increased are consistent with current literature on floricane fruiting types of blackberry which indicate that fertilizer applied in-season is generally allocated toward the primocane, however some N uptake in-season by the floricane does occur. Total plant FRE at stage 3 was 21.23%. High soil N levels at the trial site may have diluted uptake of applied 15N. These preliminary results represent the initial year findings of a multi-year trial.
