Carbon dioxide and/or temperature elevation effect on yield response, nutrient partitioning and use efficiency of applied nitrogen in wheat crop in central India

Despite several implications of excessive nitrogen (N) use on environment, information on effect of elevated carbon dioxide (CO2) and/or temperature on recovery and use efficiency of applied N are limited. Hence, this field study was carried out for three consecutive seasons of wheat crop during 2016-17 to 2018-19 in Open Top Field chambers (OTCs) under four climate conditions, viz. ambient, elevated CO2 (similar to 550 mu mol mol(-1)), elevated temperature (similar to 2.0 degrees C above ambient) and co-elevation of both CO2 and temperature. Interaction of climate and year was found non-significant (P > 0.05) for the studied parameters, but, significant effect of climate was observed in most of the parameters except straw N uptake. Pooled data analysis of three consecutive crop years indicated CO2 elevation significantly enhancing above ground biomass and grain yield and also N uptake in grain. The CO2 mediated grain yield response was to the extent of 15% (P < 0.0001) as compared to ambient, however, the yield advantage was partly offset with co-elevation of temperature. Elevation in CO2 produced 16% higher total N uptake than ambient. Co-elevation of CO2 and temperature showed a higher N uptake by about 10% as compared to ambient. In absolute terms, 25 and 15 kg ha(-1) of additional N uptake was observed under elevation of CO2, and with co-elevation of temperature, respectively. Agronomic (AE(N)) and physiological N use efficiency (PEN), recovery of applied fertilizer N (REN) and partial factor productivity (PFPN) were significantly higher under CO2 elevation. Co-elevation of temperature caused significant depletion in REN and PFPN compared to CO2 elevation. The three years' study clearly indicated significant advantage in yield and recovery of applied fertilizer N with CO2 elevation, at the cost of significantly higher N uptake. Significantly higher N removal and trend of declining soil mineral N content under elevated CO2 indicates possible N mining and N limitations may constrain the long-term plant response to CO2 elevation. The study has significance in N management for sustaining productivity and maintaining soil nutrient pool under changing climate.