Effect of Ambient Gasess on Respiration of Soil Supporting Four Crops in Central Saudi Arabia

This study was conducted at four localities (Maseef, Naseem, Oleya and Industrial City) in Riyadh city, KSA to determine the effect of increased tropospheric gases on responses of in situ soil respiration (Rs) of wheat (Triticum aestivum L. cv. Giza 68), broad bean (Vicia faba L. cv. Lara), kidney bean (Phaseolus vulgaris L. cv. Giza 3) and pea (Pisum sativum L. cv. Perfection) rhizosphere soil. These plants were grown to a full-season in pots to recieve four air quality localities treatments. Daily mean of O₃, SO₂, NO₂ and CO₂ concentrations were recorded by portable gas analyzers in the center of studied localities. The Rs values were measured monthly before seed germination, during all growth stages and after harvesting (October, December, February, April and June) at three times during the day (morning, noon and afternoon) for each stage. The maximum values recorded for O3 in mid June, 2007 were 39, 77, 95 and 166 nL L^-1, in Maseef, Naseem, Olea and Industrial City localities, respectively. Significant decreases in Rs were observed for all polluted localities in compared Maseef site (less polluted). The greatest decreases in Rs were found at Industrial City followed by Naseem and Oleya. More reductions in Rs were observed for the Industrial City treatments during flowering and grainfill stages, while normal respiration at Maseef area was recorded. This study concluded that O₃ injury can reduce the R_s by decreasing the activities and reactions in soil supporting plants.