Impacts of climate change on irrigated potato production in a humid climate

The impacts of climate change on the irrigation water requirements and yield of potatoes (Solanum tuberosum L.) grown in England have been assessed, by combining the downscaled outputs from an ensemble of general circulation models (GCM) with a potato crop growth model. The SUBSTOR-Potato model (embedded within the DSSAT program) was used to simulate the baseline and future irrigation needs (mm) and yield (t ha−1) for selected emissions scenario (SRES A1FI and B1) for the 2050s, including CO2 fertilisation effects. The simulated baseline yields were validated against independent experimental and field data using four reference sites. Probabilistic distribution functions and histograms were derived to assess GCM modelling uncertainty on future irrigation needs. Assuming crop husbandry factors are unchanged, farm yields would show only marginal increases (3–6%) due to climate change owing to limitations in nitrogen availability. In contrast, future potential yields, without restrictions in water or fertiliser, are expected to increase by 13–16%. Future average irrigation needs, assuming unconstrained water availability, are predicted to increase by 14–30%, depending on emissions scenario. The present ‘design’ capacity for irrigation infrastructure would fail to meet future peak irrigation needs in nearly 50% of years. Adaptation options for growers to cope with these impacts are discussed.