Effects of Elevated CO2 Level and N and P Supplies on two Winter Wheat Varieties in the Early Developmental Stage

Two winter wheat varieties were grown in growth chambers under controlled environmental conditions at two atmospheric CO2 concentrations (375 and 750 ppm) and different soil nitrogen and phosphorus levels. Data on plant height, tiller number, leaf number, leaf area, shoot and root dry weight were recorded in the 6th week after planting. The plants responded positively to CO2 enhancement for most of the parameters examined, producing more root and aboveground biomass. Low soil nitrogen concentrations decreased the influence of CO2 enrichment, while nitrogen at above-optimum levels tended to suppress growth. High CO2 concentration, however, had stimulating effects at inhibiting nitrogen doses. There was a shift in optimum soil N for the shoot dry weight due to the doubling of atmospheric CO2. In this young developmental stage the effect of phosphorus was not as pronounced as that of nitrogen, though P interacted with N at the highest N concentration where a positive relationship was found which moderated the inhibiting effects.