Assessing Ozone impacts on arable crops in South Asia: Identification of suitable risk assessment methods to improve crop biotechnology

This study has applied a number of different O3 risk assessment methods in South Asia to assess the extent and magnitude of O3 risk to crops and investigate how appropriate different methods are in identifying local environmental conditions and crop physiological traits that might alter crop sensitivity to O3. Concentration based methods are used in combination with tools and datasets tailored for South Asian conditions to investigate O3 impacts on wheat, rice, soybean and potato. Relative yield losses are substantially smaller (0.1 to 11.5 %) than those found in previously conducted global modelling studies (3 to 30 %) which is attributed to the improved resolution of the O3 photochemical model and crop distribution datasets used in this South Asian analysis. For the first time O3 flux based risk assessment methods are also applied for wheat in India. The stomatal conductance component of this flux method has been parameterised for Indian wheat based on available crop physiology data. Comparisons show that flux based methods tend to estimate larger relative yield losses than concentration based methods (16 % compared to 0.6 to 11.5 % for India). There are also differences in the spatial pattern of estimated risk though both methods clearly identify the Indo-Gangetic Plains as a high O3 risk region. The co-variation in O3 concentrations, crop distribution (both growth periods and geographical location), local meteorology (especially temperature and VPD) and crop physiology are all important in determining flux estimated O3 sensitivity. Finally, the flux based method is used to assess phenological traits (sowing times and maturing periods) introduced in new Indian wheat cultivars. This highlights the importance of crop phenology in determining O3 sensitivity as a function of both O3 concentration and environmental conditions and emphasises the potential application of flux based approaches as a tool capable of informing future crop biotechnology efforts.