The effects of ambient ozone (O 3) on wheat ( Triticum aestivum L.) varieties HUW 510 and LOK-1 were studied at recommended and 1.5 times recommended NPK under natural field conditions using open top chambers under varying NPK levels. Ambient O 3 was filtered out from air through charcoal filters for control plants (FCs), while non-filtered chambers received ambient O 3 (NFCs). Twelve hourly mean concentrations of O 3 varied from 10.3 to 110 ppb. Plants growing in FCs showed better growth performance and higher biomass accumulation compared to those in NFCs at both NPK levels. There were improvements in yield and its quality parameters in FCs compared to NFCs at both NPK levels with no significant difference in yield between FCs and NFCs at 1.5 times recommended NPK in LOK-1 and at RNPK in HUW 510. Nitrogen utilization efficiency increased in NFCs compared to FCs in both the varieties, but lower capability of N acquisition under ambient O 3 led to higher magnitude of reduction in yield of LOK-1 compared to HUW 510 at recommended NPK. The results clearly showed that 1.5 times recommended NPK alleviated the negative effects of ambient O 3 pollutant in LOK-1 variety whereas recommended NPK in HUW 510.
