Abstract
Studies on crop response to light quality (red (R) to far-red (FR) light ratio) often recommend early weed removal to reduce the effects of shade avoidance responses on crop yield. However, it is unclear whether crops are able to distinguish reflected light quality of kin from that of nonkin. We evaluated the response of sugar beet (Beta vulgaris L.) to reflected FR light from sugar beet, common lambsquarters (Chenopodium album L.), Kentucky bluegrass (Poa pratensis L.), alfalfa (Medicago sativa L.), and bare soil (control) under outdoor conditions in 2016 and 2017. Treatments were completely randomized with 10 replications per treatment. The study methods ensured there was no direct resource competition. The reflected R:FR of plant species ranged from 0.06 (common lambsquarters) to 0.24 (sugar beet) compared to 0.7 for the bare soil. In 2016 and 2017, there were 2 to 4 more leaves in the sugar beet surrounded by soil compared to sugar beet surrounded by neighboring species. There was up to 47, 57, 43, and 23% reduction in sugar beet leaf area, shoot dry weight, root diameter, and root dry weight, respectively, due to reflected R:FR light from neighboring species. Sugar beet did not respond differently to reflected light quality of kin compared to nonkin.