Adaptation of water and nitrogen management to future climates for sustaining potato yield in Minnesota: Field and simulation study

The present study focuses on (i) evaluation of potato crop yield under present time slice (PTS) with recommended management of nitrogen (N) fertilizer and irrigation on sandy soils of Minnesota,USA (ii) simulation of potato productivity and nitrate leaching with the SUBSTOR DSSAT-potato model in a projected future climatic environment (2038-2067) and (iii) evaluation of alternative irrigation and N management strategies with the DSSAT model as adaptation measures to minimize climate change impacts. Ensemble global climate model output for each of three future mid-century (MC) 10-years time slices of crop growing season predicts increases in maximum temperature (T_max) of 0.7, 1.2 and 2.1°C; and in minimum temperature (T_min) of 0.6, 1.3 and 2.0°C in MC1 (2038-2047), MC2 (2048-2057) and MC3 (2058-2067), respectively, during the tuber bulking periods. Rainfall (RF) of 253.1mm in PTS decreased by 29.7, 16.7 and 6.5mm in MC1-MC3, respectively. Under the changed climate, simulations indicated decreases in potato yields of 19-29%, harvest index of 4-9% and water use efficiency of 22-32% compared with current irrigation and fertilizer rates (260mm irrigation, 270kgha^-1 N fertilizer). Potato yields could be sustained at present levels by increasing irrigation levels to 390mm, with 450kgha^-1 N in the years 2038-2047; and 326 and 390mm irrigation with 450kgNha^-1 in year 2048-2057. However, leaching losses in 2048-2057 would increase (relative to current losses) by 34-62%. In the years 2058-2067 yield in the region evaluated can no longer be sustained with increased N and irrigation levels and leaching losses would increase by 41-67%. Use of varieties tolerant to drought and heat or adapting alternative cultural practices will be required to maintain productivity.