Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: November 12, 2006
Publication Date: N/A
Technical Abstract: The interaction between nitrogen application rate and carbon assimilation in potato strongly affects growth and developmental rates. Two consecutive experiments were carried out in the summer of 2005 in six sunlit, controlled environment plant growth chambers with six nitrogen application rates and two levels of CO2, 740 umol mol-1and 370 umol mol-1. The six nitrogen treatments were 2, 4, 6, 8, 11 and 14 mmol L-1 of N. Whole plant canopy photosynthesis, light interception, and transpiration were recorded at 5 and 15 minute intervals. Elevated CO2 increased tuber and root weight, but not above ground biomass in all N treatments. The differences in total biomass between the two CO2 treatments increased as N rate increased. The leaf, stem and tuber nitrogen contents in all N treatments were lower and the carbohydrate content higher at elevated CO2 than at ambient. Nitrogen rate and elevated CO2 increased the number of secondary and tertiary branches. An analysis of nitrogen uptake showed that only about 10 to 35% of N uptake was via passive N uptake (in the transpiration flow) for ambient CO2. The percentages varied from 45 to 70% for the elevated CO2. In both cases, the amount of N taken up with transpiration increased as N concentration increased. Overall, tuber yield in plants grown at elevated CO2 had a greater response to increasing nitrogen application than did plants grown at ambient CO2 levels.