Grow Tubes Change Microclimate and Bush Architecture but Have Little Effect on Bush Biomass Allocation at the End of the Establishment Year in Blueberry

Abstract

Microclimate variables were integrated over a 6-month period during which blueberry (Vaccinium corymbosum cv. Liberty) bushes were grown in 51-cm high, 20-cm diameter round grow tubes (opaque or translucent) on a sawdust mulch-covered raised bed with the mulch incorporated into tilled soil. Grow tubes were installed around plants in the spring of 2006, 5 months after planting. Total photosynthetic photon flux (PPF) density was 55% and 21% of ambient in translucent and opaque tubes, respectively. Daily maximum vapor pressure deficit consistently was highest in translucent tubes. Air (Ta) and stem (Tstem) temperatures in both grow tube types exceeded Ta and Tstem in non-tubed plants (ambient). Maximum mulch surface temperature (Tm) was lowest in opaque tubes, whereas there was no difference in Tm between ambient and translucent tubes. The soil–mulch interface temperature (Tsm) was warmer outside tubes than Tsm inside tubes. Soil temperatures directly under the tubes differed very little between tube types and ambient, generally less than 1 °C. Root and crown dry mass (DM) did not differ between tubed plants and ambient at the end of the establishment year. Leaf area, leaf DM, and fruit bud number were suppressed inside tubes. All plants were greater than 51 cm tall at the end of the growing season. Substantial compensatory growth occurred above tubes: tubed plants were more upright and had more leaf area, leaf DM, and shoot growth than ambient plants above 51 cm. However, there was no difference between tubed and ambient plants in fruit bud number, total plant leaf area, shoot:root, or DM of 1- and 2-year-old wood. Grow tubes can alter microclimate and architecture of young blueberry bushes but have no significant influence on size and distribution of total DM after one growing season in the field.