Effects of free air CO ₂enrichment on root growth of barley, sugar beet and wheat grown in a rotation under different nitrogen supply

Elevated atmospheric CO2 concentrations [CO2] are known to change plant growth by stimulation of C3 photosynthesis and by reduction of transpiration of both C3 and C4 crops. In comparison to the information on above ground plant responses only limited knowledge exists on the response of root growth of arable crops to elevated [CO2] which is particularly true for temperate crop species under real field conditions. A free air CO2 enrichment (FACE) study (550 ppm at daylight hours) was carried out in a crop rotation of winter barley, sugar beet and winter wheat repeated twice in the course of six years on a sandy loam soil at Braunschweig, Northern Germany. Winter barley and sugar beet were included for the first time in a FACE study. A possible interaction with restricted nitrogen (N) supply was studied by fertilizing the CO2 treatment plots with adequate and 50% of adequate N supply...