Volume 72 Number 2 Article 4 Pages: 101-112
Year 2018 Month 4
Title: Root Distribution of 'Brightwell' and 'Premier' Rabbiteye Blueberries as Influenced by Pecan Shell Mulch
Authors: Ashley A. Hoppers, James D. Spiers, J. Raymond Kessler, Jr., Amy N. Wright, and Arlie A. Powell
Citation
Abstract:
Pecan (Carya illinoinensis [Wangenh.] K. Koch) shell waste lacks effectual, economic disposal.
If shells could
be repurposed as mulch, then growers may be able to treat shell byproduct as a resource.
In 2016, root distribution
and growth of 'Brightwell' and 'Premier' rabbiteye blueberries (Vaccinium virgatum Aiton syn.
V. ashei Reade)
was examined using the HorhizotronTM. Each HorhizotronTM had four wedge-shaped quadrants filled with 10 cm
of an amended 80% pine bark and 20% sand (by volume) substrate, then 7.6 cm of "fresh" pecan shells (FPS),
"aged" pecan shells (APS), pine bark nuggets (PB), or an unamended 80% pine bark and 20% sand substrate
(PBS). Growth was determined weekly by measuring the horizontal root length (HRL) and root depth (RD) of
the five longest roots on either side of a quadrant.
Roots that grew into the substrate and mulch treatment layers
were not measured separately. 'Premier' HRL showed roots in FPS grew a shorter distance across the quadrant
profile than roots in PBS, but had similar HRL with APS and PB. In 'Brightwell', both shell treatments had shorter
HRL across the quadrant than the roots in PB and PBS. RD measurements for 'Premier' showed roots generally
initiated at the same depth for FPS, APS and PB, though the roots in PBS had shallower growth than the roots in
PB and FPS. 'Brightwell' RD showed roots initiated more into the upper portions of the quadrant profile in APS
and PBS than in FPS or PB. Root system architecture was reflected in root dry weight (RDW). For both cultivars,
substrate layer RDW was similar across all treatments, but mulch layer RDW varied.
Though APS had a higher
mulch layer RDW than the PB treatment in ‘Premier’, differences in RDW within the mulch layer did not impact
total root dry weight (mulch layer RDW + substrate layer RDW). In 'Brightwell', APS had a higher RDW than
FPS and PB, though PBS was similar to both APS and FPS. Unlike ‘Premier’, total RDW in 'Brightwell' was
impacted by differences in mulch layer RDW, as the quadrants that contained FPS and PB had a lower total root
dry weight than the quadrants containing APS and PBS. These results indicated that root growth in pecan shells,
as compared with root growth within and below pine bark, was not hindered.
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