Competition between sugarbeet and Sinapis arvensis and Chenopodium album, as affected by timing of nitrogen fertilization

Abstract

The effects of timing of N fertilization (early, standard or late) on competition between two sugarbeet cultivars (Ritmo, semi‐prostrate; and Rizor, erect) and two weeds (Sinapis arvensis and Chenopodium album) were studied over 2 years at Viterbo. In both years, time of N fertilization did not influence biomass, yield and yield quality of the weed‐free crop, but early N fertilization gave higher crop biomass reduction in the presence of S. arvensis and lower crop biomass reduction in the presence of C. album. Root and sucrose yield responded to competition in the same way as biomass. However, percentage reductions were higher, as both weeds affected harvest index. The two cultivars showed the same response to competition. At the weed densities studied, crop competitive ability was favoured by late N fertilization in the presence of S. arvensis and by early N fertilization in the presence of C. album. Crop competition only reduced seed production by C. album but lowered seed germination of both weeds.