More extreme and frequent drought periods reduced crop production and altered stable isotope ratios of C and N in plants

Climate change scenarios predict more frequent and intense drought periods for 2071–2100 in the most important and intensively used agricultural region of Austria, the Marchfeld. Current and predicted lower precipitation scenarios were simulated at a lysimeter station for 9 years. Plant biomass, nitrogen (N) and carbon (C) content, and δ¹³C and δ¹⁵N values of plant compartments were monitored in years 7–9. Aboveground biomass of cereals and grain yield decreased under the predicted scenario, while the quality of grain (% N) was unaffected. Weed and catch crops grown in winter were not affected or were even positively affected, possibly due to the accumulation of nutrients in the soil following the lower plant uptake in summer. Accordingly, low plant δ¹⁵N values were mainly attributed to the presence of higher proportion of mineral fertilizer in the predicted precipitation scenario. As expected, water stress significantly increased δ¹³C values in plants grown over summer, while this was not seen for plants growing over winter. Fertile agricultural soil might ameliorate but cannot outbalance the negative impact of more frequent and intense drought periods.