Effect of fertilization, tiller cutting and environment on plant growth and yield of European blueberry (Vaccinium myrtillus L.) in Norwegian forest fields

Abstract

Abstract. BACKGROUND:European blueberry (E. blueberry; Vaccinium myrtillus L.) is a natural resource demanded by the processing industry with potential of domestication. Therefore an investigation of the possibilities of partial cultivation of native stands was started. OBJECTIVE: To increase knowledge of how E. blueberry react to soil types, climate, mineral nutrition, organic amendments and cutting of tillers. METHODE: Five forest fields with E.blueberry stands in Norway were examined. Besides natural development influenced by soil parameters and climate, effect of fertilization and plant pruning were examined in the municipalities of Bardu in Troms county (68• N) and of Snåsa and Lierne in Nord-Trøndelag county (64 • N). Experiments were executed in randomized block designs in forest fields of native E. blueberry stands. RESULTS:The fields that performed best had O-layers close to 7 cm or thicker. The C/N ratios indicate that N was not easily available in any field, and addition of mineral fertilizer containing nitrogen and phosphor show that especially N increased elongation of long shoots and more nodes were developed. However, the effect on number of short shoots per long shoot initiated a growth gain only the last of two years. The positive growth effect of fertilizer was not followed by higher yields throughout the years, and strongest fertilization level (N60P40) reduced yield in average of four years. Adding composted wood chips or wood chips alone increased tiller growth in the birch-field in Bardu both years, but only the first year in the pine-field; this was not reflected in higher yield. Cutting of shoots to the ground reduced yield and full yield potential was not recovered before the third year after cutting. CONCLUSION: The results suggest that by improving growth conditions, especially by securing a thick natural O-layer and adjusting soil macro nutrient composition, growth conditions could be improved; and that fruit yield were down the two first years after pruning.

Continuous picking may increase bilberry yields

“…The findings of increased fruit production and fruit set of bilberry in our study suggest enhanced bilberry yields in areas under continuous picking. These results are not in accordance with several previous studies suggesting that biomass loss and mechanical damage due to the natural herbivory (Fernández-Calvo and Obeso 2004; Hegland et al 2005) or clipping cause reductions in bilberry fruit production and fruit set (Mathisen et al 2010;Nestby et al 2014;Pato et al 2016). A number of references support our findings of increased berry production and fruit set of bilberry after biomass loss.…”

“…Bilberry fruit production is associated with current annual shoot size (Tolvanen and Laine 1997;Fernández-Calvo and Obeso 2004) and is linked to the ability of bilberry to produce new growth after biomass loss. In this study bilberry lost annually less than 0.5% of its total standing biomass, which is far more than 50 times lower as compared to the 25% to 100% biomass loss applied by clipping in most of the studies on bilberry performance (Tolvanen et al 1994;Nestby et al 2014;Pato et al 2016). The recovery time after severe damage takes several years (Tolvanen et al 1994;Hautala et al 2008), during which vegetative recovery prevails and bilberry fruit production is postponed (Tolvanen et al 1993b;Nestby et al 2014).…”

“…In this study bilberry lost annually less than 0.5% of its total standing biomass, which is far more than 50 times lower as compared to the 25% to 100% biomass loss applied by clipping in most of the studies on bilberry performance (Tolvanen et al 1994;Nestby et al 2014;Pato et al 2016). The recovery time after severe damage takes several years (Tolvanen et al 1994;Hautala et al 2008), during which vegetative recovery prevails and bilberry fruit production is postponed (Tolvanen et al 1993b;Nestby et al 2014). For example, Stark et al (2010) reported that already a one-time 20% biomass loss from the top of the ramets of bilberry postpones bilberry fruit production for two years.…”

“…Natural herbivory induces plant chemical defense responses (Koo and Howe 2009), and, hence, is not totally analogous to biomass loss by commercial berry picking, despite similar mechanical damages (Seldal et al 2016). However, bilberry fruit production has been found to be reduced both under natural herbivory (Fernández-Calvo and Obeso 2004;Hegland et al 2005Hegland et al , 2010, as well as in studies mimicking herbivory (Tolvanen et al 1993b), and after clipping (Stark et al 2010;Nestby et al 2014) due to the allocation of resources to increased vegetative growth. Long-term vegetation changes towards more fast-growing graminoids in vegetation after biomass loss by clipping may lead to a lower sexual reproduction of bilberry (Mathisen et al 2010) and bilberry yields.…”

The effect of NP fertilization on European blueberry (Vaccinium myrtillus L.) development on cultivated land in mid-Norway

“…Fertile locations are more favorable than poor locations; some studies have shown that forests of medium fertility produce the largest EB yields in the boreal zone. It was also found that N and P fertilization over four years in forest fields of EB increased shoot growth, but had generally neutral or negative effect on fruit yield depending on the NP level [14]. EB have a shallow and weakly developed root system, but the biomass of rhizomes and roots may be of a similar volume as the above ground part.…”