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Location: Horticultural Crops Research

Title: Above- and below-ground microclimate of grow tubes in an organic mulch-incorporated, raised bed system for blueberry

item Tarara, Julie
item Chaves, Bernardo
item Strik, Bernadine

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2013
Publication Date: 11/15/2013
Citation: Tarara, J.M., Chaves, B., Strik, B.C. 2013. Above- and below-ground microclimate of grow tubes in an organic mulch-incorporated, raised bed system for blueberry. HortScience. 48:1363-1369.

Interpretive Summary: Grow tubes are plastic cylinders that blueberry growers place over new plants to improve the establishment of the bushes in their first year on the farm. The grow tubes raise temperatures inside them, which promotes growth. However, they also reduce the light that reaches the plant, which can retard growth. In a field in which young blueberries with grow tubes were grown on organic mulch, we measured the temperature of the air, the mulch, and the soil inside the tubes and outside. Air temperatures were much higher inside the tubes than outside. The temperature of the organic mulch was lower inside the tubes because there was less sunlight to warm the mulch surface. Soil temperatures did not differ between inside the grow tubes and outside of a tube. Because of these temperature differences, grow tubes should promote the growth of the shoots and leaves of young blueberry plants but are not expected to have an effect on the growth of roots.

Technical Abstract: Grow tubes are well established in forestry and are gaining attention in establishing some woody perennial crops. To date, microclimate descriptions have addressed the above-ground environment, but a mulched raised bed system with organic mulch-incorporated soil requires both above- and below-ground microclimate to be quantified. We measured the microclimate of commercially used, non-ventilated translucent and non-ventilated opaque grow tubes in a model crop of blueberry (Vaccinium corymbosum L.) grown on sawdust-mulch covered raised beds formed from sawdust-incorporated tilled soil. The differences in air temperature between tubes and ambient were consistent with those reported in the literature. Air temperature in translucent tubes was up to 19.7 C higher than ambient. Differences in vapor pressure deficit were largely a function of differences in air temperature between tubes and ambient rather than actual vapor pressure. Stem temperatures were highest outside of the tubes due to radiation load. The surface temperature of ambient sawdust mulch (maximum 53 C) was up to 14 C above that in the translucent tube and 20 C above that in the opaque tube. The largest gradients in the bed system were between the loose dry mulch and the soil-mulch interface. The presence of a grow tube did not influence soil temperature or its daily amplitude at 15 cm below the surface—the native tilled soil. Temperatures associated with the opaque tubes were between ambient and those in the translucent tubes. The temperature data indicate that both opaque and translucent unventilated grow tubes should influence shoot and crown growth but may have little influence on root growth in this shallow-rooted plant.