Ultraviolet-B radiation and nitrogen effects on growth and yield of maize under Mediterranean field conditions

The effects of an increase in UV-B radiation on growth and yield of maize (Zea mays L.) were investigated at four levels of applied nitrogen (0, 100, 200 and 300 kg ha-1 of N) under Mediterranean field conditions. The experiment simulated a 20% stratospheric ozone depletion over Portugal. Enhanced UV-B and N deficiency decreased yield and total biomass production by 22¯49%. High UV-B dose reduced yield, total biomass and growth of Nfertilized maize plants but did not affect N-stressed plants to the same extent. The response of grain yield to N was smaller with enhanced UV-B radiation. The underlying mechanisms for these results are discussed.