2018 ASHS Annual Conference

The strawberry production season in Florida and many other winter production regions is characterized by excessive heat during fall establishment and cool, sometimes freezing, temperatures during peak production. To mitigate seasonal temperature extremes, new plastic mulch films that are white or metalized in the center and black on the shoulders have been recently developed. Our previous studies demonstrated that these striped plastic mulches improve fruit earliness, allowing growers to advance planting dates from October to September by reducing heat stress during transplant establishment. To characterize microenvironment modification by striped plastic mulches, we monitored several soil and canopy microenvironment variables during the 2017–18 winter strawberry growing season in Balm, FL. We evaluated entirely black plastic mulch (black mulch) against black plastic mulch with either a 51-cm wide white or aluminum center stripe (white-striped and metalized-striped mulch, respectively), using the short-day cultivar ‘Florida Radiance’. Bare-root transplants were established in raised beds on 28 Sept. 2017. Thirty harvests were performed from mid-November through February. White-striped and metalized-striped mulches increased the early-season marketable yield by 40% and 52%, respectively, and the total season marketable yield by 26% and 34%, respectively, confirming the beneficial effects of these mulches on strawberry yield and earliness. Root-zone temperatures measured at a 10-cm depth under both striped mulches were reduced by 3°C compared to black mulch throughout the hot afternoons of October and November. For the same time periods, crown tissue temperatures monitored over the striped mulches via a fine-wire thermistor showed a reduction of up to 2 °C compared to black mulch. Spectroradiometric measurements in the late season showed that even within a well-shaded canopy, photosynthetically active radiation reflected by the mulch surface increased by 349% for white-striped mulch and 302% for metalized-striped mulch compared to black mulch. Spectroradiometric measurements also showed that, compared to black mulch, white-striped mulch decreased the ratio of red to far-red light within the canopy, which may play a role in floral bud induction for short-day strawberry cultivars. In summary, the changes in microenvironments with striped mulches can be characterized by cooler soil and crown temperatures during establishment, increased potential light capture, and far-red light enrichment. These results demonstrate that striped mulches optimize microenvironments to a comparable extent and serve as a feasible strategy to improve yield and earliness for winter and spring strawberry producers.