2017 ASHS Annual Conference

Our objective was to determine the impact of cultivar (‘Duke’, ‘Liberty’), mulch (sawdust, weed mat), and fertilizer source (feather meal, fish solubles) on allocation of dry biomass over two years in mature northern highbush blueberry (Vaccinium corymbosum) grown under long-term organic management. Plants were grown on raised beds, fertilized annually with 57–140 kg·ha^-1 N (140 kg·ha^-1 N during the study period), drip irrigated, and weeds controlled. Whole plants were dug at the green fruit stage and post-harvest in 2015, and at dormancy in 2015–2016 and separated into parts. Ripe fruit were hand-harvested. ‘Liberty’ had greater leaf biomass at senescence in 2015–2016 than ‘Duke’ (0.49 vs. 0.29 kg/plant, respectively), produced more whip biomass (0.025 vs. 0.013 kg/plant) at the green fruit stage, and had heavier crowns when dormant in 2016 (1.43 vs. 0.92 kg/plant). At green fruit stage, ‘Liberty’ produced more leaf biomass when fertilized with feather meal, with no effect in ‘Duke’. In contrast, ‘Duke’ produced more stem biomass at this stage when fertilized with fish, with little effect in ‘Liberty’. Long-term fertilization with feather meal produced larger root biomass at all four stages compared to fish; differences in root biomass ranged from 44–67%, with the greatest effect at dormancy. Fertilization with feather meal led to greater crown biomass at all stages except dormancy, 2015. At dormancy, 2016, wood biomass was greater when fertilized with feather meal than fish. Feather meal increased leaf biomass at the green fruit stage by 24% compared to fish. Total plant biomass was 26% and 40% greater with feather meal than fish at green fruit stage and dormancy, 2016. There was a cultivar by fertilizer by mulch interaction on 1-year-old wood biomass at dormancy, 2015. Sawdust mulch increased stem biomass with feather rather than fish for ‘Liberty’, but the opposite was found in ‘Duke’. With weed mat, ’Liberty’ had greater stem biomass with fish than feather, with the opposite in ‘Duke’. At dormancy, weed mat led to increased leaf (28%) and 1-year-old stem (52%) biomass in 2015 and 2016, respectively, than sawdust. ‘Liberty’ produced greater fruit biomass (yield) in 2015 (52%) and 2016 (83%) than ‘Duke’. There was no effect of fertilizer source or mulch on yield. The greatest impacts on biomass allocation in these long-term organic production systems were cultivar and fertilizer source; mulch type had relatively little effect on plant biomass or allocation over the 2-year study.