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The fate of 15N labeled urea in a soybean-wheat cropping sequence under elevated CO2 and/or temperature

Lenka, Narendra Kumar, Lenka, Sangeeta, Mahapatra, Prabhakar, Sharma, Niharika, Kumar, Sanjeev, Aher, Satish B, Yashona, Dharmendra Singh
Agriculture, ecosystems & environment 2019 v.282 pp. 23-29
carbon dioxide, carbon dioxide enrichment, climate change, climatic factors, cropping sequence, crops, fertilizers, grain yield, harvesting, metabolism, nitrogen, seed yield, seeds, soil, soybeans, stable isotopes, temperature, total nitrogen, urea
Changing climate has direct linkage with growth and metabolism in plants and is likely to alter nitrogen (N) uptake from fertilizers. Hence, a field study was conducted using 15N labeled urea in micro-plots to study the effects of elevated CO2 and/or temperature on fertilizer-N use in a soybean-wheat cropping sequence. Crops were grown in open top field chambers (OTCs) under two CO2 (386 and 558–561 ppmv), two temperature (ambient, 1.4-1.5 °C above) and three N levels during 2017-18. The N treatments were 50, 100 and 150% of the recommended dose (N50, N100 and N150). Labeled (15N) urea (10% atom excess) was applied to soybean. Elevated CO2 and/or temperature showed significant effects on seed yield, total N uptake, fertilizer-N uptake, per cent N derived from fertilizer (Ndff) and per cent fertilizer-N use in the soybean-wheat crop sequence. Total N uptake in soybean significantly increased under elevated CO2 and/or temperature treatments, mainly due to higher N uptake in seeds. Effect of climate on fertilizer-N uptake and utilization in the soybean-wheat cropping sequence varied with level of N application. The 15N labeled fertilizer-N uptake and per cent fertilizer-N use was significantly higher under co-elevation of both CO2 and temperature at N100 and N150, but, was mostly similar among the climate treatments at N50. In the soybean-wheat crop sequence, 13–40% of the applied fertilizer was used, with significantly higher use with co-elevation of both CO2 and temperature. Out of the applied fertilizer, 20–51% got retained in the surface soil and 43–73% was traced in the soil-plant system. Significantly higher fertilizer-N use in the soybean-wheat crop sequence under co-elevation of CO2 and temperature indicates increasing role of fertilizer-N to harvest the CO2 mediated enhancement in grain yield under the future climate conditions.