Modelling climate impacts on crop yields in Belgium

In the last 2 decades, Belgium has experienced more monthly extremes than in any other decade since observations began in 1833. During the past 60 yr, yields have increased, on average, by 0.1 t ha(-1) yr(-1) for winter cereals, 0.4 t ha(-1) yr(-1) for potato and 0.6 t ha(-1) yr(-1) for sugar beet. A total of 60 to 74% of the variability in yields between 1960 and 2008 was explained by meteorological variables. Multivariate analysis showed significant statistical relationships between yield and vapour-pressure deficit, temperature and growing season length, and water logging and drought. These variables were therefore included in a new regional dynamic crop model (REGCROP) developed to assess climate impacts on regional arable crop production. Nash-Sutcliffe model efficiencies were between 0.68 and 0.84 between simulated and observed national yields for the period 1960-2008. REGCROP was subsequently run for 3 climate change scenarios and 3 typical Belgian soils (clay, loam and loamy sand) and climate impacts were compared with historical weather impacts (1960-1989). Higher temperatures increase crop development and shorten the growing season. Strong projected changes in seasonality affect cumulative drainage for both winter and summer crops and result in a drier water balance regime with climate change. Average yield losses of 12 to 27% were simulated for sugar beet and 23 to 44% for potatoes owing to drought and heat stress. Projected losses for winter cereals are 5 to 12%, mainly owing to waterlogging, whereas yield increases up to 6 or 7% are projected as a result of temperature increases and favourable vapour-pressure deficits.