Effects of nutrient (NPK) supply on faba bean response to elevated atmospheric CO2

Abstract

The effects of increased atmospheric CO2 on crop growth and dry matter allocation may change if nutrient supply becomes insufficient for maximal growth. 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 for faba bean, pot experiments have been carried out in two glass houses at ambient and doubled CO2 concentration. Bean plants were grown at different supplies of N, P or K. Doubling of atmospheric CO2 resulted in a strong increase (+100%) in total yield. This CO2 effect disappeared rapidly with increasing nitrogen, phosphorus or potassium shortage. Doubling of atmospheric CO2 resulted in no change in minimum nitrogen concentration and a nil to slight decrease in minimum phosphorus concentration in crop residues. Nutrient requirements to attain a certain yield level might change with a future increase in atmospheric CO2. However, such conclusions cannot yet be drawn because nutrient concentrations in seeds were not available.