Drought–flood abrupt alternation events increase soil nitrogen loss via surface runoff in a typical grain base in China

Northern Anhui Plain, China. This study analyzed the nitrogen (N) mitigation (N storage in soil, plants, and surface runoff) under drought–flood abrupt alternation (DFAA) in summer maize farmland systems based on field experiments. Soil N loss due to DFAA in the summer maize planting area of the Northern Anhui Plain was simulated based on the critical threshold obtained from the field experiments. The experimental results showed that DFAA events reduced soil N storage and plant N storage by 14.9 % and 54.1 % compared to the control systems, respectively, while N storage in the water component of surface runoff in the DFAA treatments was 54.1 % higher. Numerical simulations revealed that the proportions of average annual soil N loss in topsoil were 14.98–19.58 % from 1964 to 2017 and 10.22–22.75 % from 2020 to 2050 in the study area. The highest average annual soil N loss shifted from the southwestern to the central and southeastern Northern Anhui Plain. The highest soil N loss in the hypothetical natural scenario was 49.0 % and 46.7 % lower compared to historical and future scenarios, respectively. The findings indicate that DFAA has significantly negative impacts on water quality. The quantitative analysis provides a reference for developing targeted regulation measures for the Northern Anhui Plain facing compound extreme events. • Drought-flood abrupt alternation (DFAA) reduced the soil N storage around 14.9 %. • DFAA increased soil N loss in surface runoff (water part) by 54.1 %. • Soil N loss in surface runoff is 31.4 % higher in the future. • The highest soil N loss was higher by 45 % than that in natural conditions.