Long-term effects of burn-pruning on lowbush blueberry (Vaccinium angustifolium Ait.) production

Burning is a pruning technique used to improve productivity of lowbush blueberry fields. Growers, however, are concerned that continuing and frequent burning might reduce production and eventually destroy blueberry fields. To assess the effect of long-term spring burn-pruning on blueberry production and the surface organic layer, 2-, 3- and 4-yr burning cycles were studied for 24 yr on a previously unfertilized natural stand of lowbush blueberry. Mean annual yield (averaged over burn and crop years) decreased with increases in the interval between burning due to decreased production in the second and third crop years following burning. Yield in the third crop year was similar to that from the unburned check plots. There was no significant yield decrease between the first 12 yr (period 1) and the second 12 yr (period 2) of production for the 2-yr cycle, but there were declines for the 3- and 4-yr cycles due mainly to lower yields in the second crop. Lower second-crop yields in the second period was attributed to damage by the blueberry leaftier (Croesia curvalana Kft.). Mean annual ripe fruit yields for the 2-, 3- and 4-yr cycles and unburned check were 473, 458, 335 and 109 kg ha−1, respectively, in period 1 and 478, 340, 277 and 38 kg ha−1, respectively, in period 2. Burning did not decrease the depth of the surface organic layer. Key words: Lowbush blueberry, Vaccinium angustifolium, burning, pruning, organic matter, yield, berry weight, flower buds, residual maximum likelihood