Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/1999
Publication Date: N/A
Interpretive Summary: Many strawberry growers use black plastic mulch over drip irrigation systems to control water supply in the root zone, warm the soil in spring, control weeds with less herbicides, and keep fruit clean. In previous work, we developed a red plastic mulch that keeps those benefits and also reflects a light wavelength ratio that acts through the natural growth regulating phytochrome system within growing plants to direct more new growth to the developing fruit. The colored mulch technology has been licensed to industry and it is now marketed as Selective Reflective Mulch (SRM). In the present 2-year study, strawberry plants were grown over SRM-Red versus standard black plastic mulch at the USDA-ARS Coastal Plains Research Center near Florence, SC, and on a commercial strawberry farm near Johnston, SC. Yields were higher and berries were larger over the red mulch each year at each location. The percentage increase in strawberry fruit size over the new red versus the standard black mulch was greater than the percentage increase in tomato fruit size over the red versus black mulches in the previous study. The greater size response of strawberry fruit may have occurred because the strawberries developed closer to the red reflecting surface than the tomatoes. We are presently analyzing strawberry fruit that developed and ripened over red versus black plastic mulches for nutrient and flavor components.
Technical Abstract: Plastic mulches are frequently used in raised-bed culture of strawberry (Fragaria x ananassa) to conserve water, control weeds with less herbicides, and keep fruit clean. The most commonly-used plastic mulch color is black. We hypothesized that a specially formulated red plastic mulch that reflects a higher far-red to red photon ratio could regulate photosynthate allocation enough to increase yield of strawberry. Yields over the red plastic were compared with those over standard black plastic in field experiments at a research center and on a commercial strawberry farm. Yield per plot and size per berry were greater over the red than over the black plastic at both locations. The yield advantage of red mulch relative to black occurred whether the red plastic was placed directly over the soil or over a layer of black plastic which blocked light from the soil surface. We conclude that strawberries were larger over the new red plastic mulch because reflected light affected phytochrome-mediated allocation of more photosynthate to developing fruit.