Effects of oxidants on soybean growth and yield in the Pakistan Punjab

Plants of soybean (Glycine max L.) were grown with and without the ozone pr otectant EDU (N-[2-{2-oxo-1-imidazolidinyl} ethyl]-n2 phenylurea) at a subu rban site, a remote rural site and a rural roadside site around the city of Lahore, Pakistan. The development and yield of the plants was determined i n two experiments - one immediately post-monsoon and one in the following s pring (pre-monsoon). Concentrations of nitrogen dioxide and photochemical o xidants were measured at each site. The effect on yield of EDU at the subur ban site (47 and 113% increase in seed weight per plant relative to the unt reated plants in the post- and pre-monsoon experiments, respectively) was s imilar to the effects of filtration on yield of soybean in a parallel open- top chamber study at the same site (77% increase relative to plants subject ed to unfiltered air for the pre-monsoon experiment). Effects of EDU on yie ld were greater at both rural sites than at the suburban site in both exper iments, and greater in the spring experiment (182% at the remote rural site and 285% at the rural roadside site) than in the post-monsoon experiment ( 94% at the remote rural site and 170% at the rural roadside site); oxidant concentrations were also greater at the rural sites than at the suburban si te, and greater in the spring experiment than the post-monsoon experiment. The results imply that ozone may be causing significant crop losses in rura l areas around Lahore; however, the geographical extent of the problem, and the implications for peri-urban agriculture around other cities of south A sia are uncertain. (C) 2001 Elsevier Science Ltd. All rights reserved.