Impact of nitrogen and weeds on glyphosate-resistant sugarbeet yield and quality.

摘要

The commercialization of glyphosate-resistant sugarbeet has changed weed management in sugarbeet. Many growers are delaying their initial herbicide application because glyphosate can control larger weeds, which allows weeds to compete with crops for nutrients. Greenhouse and field experiments were conducted to examine the effect of nitrogen (N) rate and the competitive ability of weeds on glyphosate-resistant sugarbeet. In the greenhouse at a 1:1 sugarbeet: weed proportion, sugarbeet was able to assimilate more N and produced more biomass than common lambsquarters or Powell amaranth. Field experiments however, determined N assimilation by weeds was 3 to 4 times greater than sugarbeet on a per hectare basis early in the growing season. Higher weed densities in the field may have been responsible for decreased N assimilation by sugarbeet. Highest sugarbeet root yields were always achieved at the highest N rates (134 kg and 67:67 N ha-1), and were greater when weeds were controlled early ( 2 cm tall). When weeds were not controlled prior to 8 cm, a 15% yield reduction was observed. Recoverable white sucrose per ha (RWSH) was highest at rates ≥ 100 kg N ha-1 in three of the four location by year combinations. RWSH was 8 to 16% lower if weeds were not controlled until they were 8 cm tall. Weeds prevent sugarbeet from utilizing available water, light, and nutrients, and should be controlled prior to 8-cm heights to avoid negative impacts on N assimilation, root yield and sucrose production.