Container Type and Substrate Affect Root Zone Temperature and Growth of ‘Green Giant’ Arborvitae

Abstract

Root zone temperature (RZT) in nursery containers commonly exceeds ambient temperature during the growing season, negatively impacting crop growth and quality. Black nursery containers absorb radiant heat resulting in excessive RZT, yet other types of containers and different substrates can moderate RZT. We conducted studies in Tennessee and Alabama to evaluate the effects of container type and substrate on RZT and growth of 'Green Giant' arborvitae (Thuja standishii × plicata 'Green Giant'). Trade gallon arborvitae were transplanted into black, white, or air pruning containers filled with pine bark (PB) or 4 PB: 1 peatmoss (v:v) (PB:PM). Plants grown in PB:PM were larger and had greater shoot and root biomass than plants grown in PB, likely due to increased volumetric water content. Plant growth response to container type varied by location, but white containers with PB:PM produced larger plants and greater biomass compared with the other container types. Root zone temperature was greatest in black containers and remained above 38 • C and 46 • C for 15% and 17% longer than white and air pruning containers, respectively. Utilizing light color containers in combination with substrates containing peatmoss can reduce RZT and increase substrate moisture content thus improving crop growth and quality.

Container Color and Compost Substrate Affect Root Zone Temperature and Growth of “Green Giant” Arborvitae

“…"Green Giant" arborvitae is considered a heat tolerant plant and readily adaptable to various soil types [21]. Nevertheless, results of the present study support previous work by Witcher et al [17] where "Green Giant" arborvitae grown in white containers grew larger and produced more biomass compared with black containers.…”

“…Plant species such as "Green Giant" arborvitae (Thuja standishii × plicata 'Green Giant') may be considered heat tolerant and adaptable to various soil types yet can be sensitive to high RZT and reduced moisture level. For example, "Green Giant" arborvitae grew larger and produced more root biomass in white containers compared to black containers due to extended exposure to RZT over 38 • C [17]. In the same study, peatmoss-amended substrate resulted in larger plants due to increased volumetric water content (VWC) compared to pine bark alone.…”

Transpiration increases under high‐temperature stress: Potential mechanisms, trade‐offs and prospects for crop resilience in a warming world

“…Such unnatural soil temperatures are routinely observed in horticultural nurseries under ‘normal’ air temperatures and, as a result, could be expected to be higher in experiments where high‐temperature stress treatments are applied. To counteract such effects, it has been recently found that using light‐coloured or white pots containing substrate mixtures maximizing soil volumetric water content could help reduce root zone temperature by up to 7–8°C (Witcher, Pickens, & Blythe, 2020a, 2020b). Deploying field‐based experimental set‐ups : conducting in situ studies where the above‐mentioned environmental drivers are closely monitored will be particularly valuable to evaluate hypotheses and outcomes obtained based on controlled‐environment approaches.…”

“…Such unnatural soil temperatures are routinely observed in horticultural nurseries under 'normal' air temperatures and, as a result, could be expected to be higher in experiments where high-temperature stress treatments are applied. To counteract such effects, it has been recently found that using light-coloured or white pots containing substrate mixtures maximizing soil volumetric water content could help reduce root zone temperature by up to 7-8 C (Witcher, Pickens, & Blythe, 2020a, 2020b.…”

Horticultural Crop Response to Different Environmental and Nutritional Stress

“…The effect of environment conditions (temperature, rainfall, altitude, soil types, hail) [5][6][7][8][9], nutritional strategies [5,6,[10][11][12][13][14], water (stress, salinity) [5,8,12,15], container substrate of cultivation [16] on yield, yield traits and quality were analyzed in different crops in an open field [8,9,13,14,17] and greenhouses [5][6][7][10][11][12]15,16].…”