Effects of nutrient (NPK) supply on sugar beet response to elevated atmospheric CO2

The effects of increased atmospheric CO2 on crop growth and dry matter allocation may change if nutrient supply becomes insufficient. Increased atmospheric CO2 may also cause changes in maximum dilution of nutrients in plant tissue and hence, in the minimum nutrient concentration levels and the maximum yield-nutrient uptake ratios of crops. To study these effects of increased CO2 for sugar beet (Beta vulgaris L.), pot experiments have been carried out at ambient and doubled CO2 concentration. Beet plants were grown for four monthes at different supplies of N, P or K. Doubling of ambient CO2 resulted in a moderate increase in total yield (+24%) and beet yield (+34%), however this CO2 effect disappeared with increasing nutrient shortage (in particular nitrogen). CO2 doubling did not result in significant changes in the minimum nutrient concentrations in leaves and beets.