White-striped plastic mulch reduces root-zone temperatures during establishment and increases early season yields of annual winter strawberry

摘要

Early-season yields are critical to winter strawberry (Fragaria x ananassa Duch.) production in Florida and other winter and spring production regions around the world. Although advancing planting dates is a common practice to improve earliness, it can increase heat stress during establishment, especially on black plastic mulch. This problem could be addressed by adding a white center stripe to black plastic mulch. The white center stripe should cool the root zone during establishment while the black bed shoulders remain exposed to the sun to warm the soil during the winter. We conducted three field trials across two seasons to compare black plastic mulch (black mulch) to black plastic mulch with a white center stripe (white-striped mulch) using three cultivars (Florida Radiance, Florida Beauty, and Florida Brilliance). Bare-root transplants were planted on 26 Sept. in 2015 and 29 Sept. and 17 Oct. in 2016. Compared to black mulch, white-striped mulch reduced root-zone temperatures (10-cm depth) under the white stripe by up to 4.5 degrees C in November, while maintaining the same soil warming capacity on the bed shoulders throughout the growing season. White-striped mulch treatments resulted in increased growth, earliness, and yields, although the magnitude of improvement depended on cultivars and seasonal weather conditions. Early-season ambient temperatures were unusually high in the 2015-16 trial and the 2016-17 later-planted trial. In these two trials, white-striped mulch increased early yields by 20%-31% across cultivars. In the 2015-16 trial, white-striped mulch also increased canopy area by 11% during the early harvest period and root biomass by 26% at the end of the trial. Because late-season yields were unaffected in all trials, white-striped mulch only improved total yields for the second planting of 2016-17. By contrast, cultivar-specific effects were only observed for the first planting of 2016-17, in which white-striped mulch improved early and total yields of 'Florida Radiance' by 46% and 28%, respectively, compared to black mulch. Our results suggest that white-striped mulch is an easily implementable strategy for improving earliness of winter strawberry production in warm climates.