A probabilistic assessment of climate change impacts on yield and nitrogen leaching from winter wheat in Denmark

Abstract

Abstract. Climate change will impact agricultural production both directly and indirectly, but uncertainties related to likely impacts constrain current political decision making on adaptation. This analysis focuses on a methodology for applying probabilistic climate change projections to assess modelled wheat yields and nitrate leaching from arable land in Denmark. The probabilistic projections describe a range of possible changes in temperature and precipitation. Two methodologies to apply climate projections in impact models were tested. Method A was a straightforward correction of temperature and precipitation, where the same correction was applied to the baseline weather data for all days in the year, and method B used seasonal changes in precipitation and temperature to correct the baseline weather data. Based on climate change projections for the time span 2000 to 2100 and two soil types, the mean impact and the uncertainty of the climate change projections were analysed. Combining probability density functions of climate change projections with crop model simulations, the uncertainty and trends in nitrogen (N) leaching and grain yields with climate change were quantified. The uncertainty of climate change projections was the dominating source of uncertainty in the projections of yield and N leaching, whereas the methodology to seasonally apply climate change projections had a minor effect. For most conditions, the probability of large yield reductions and large N leaching losses tracked trends in mean yields and mean N leaching. The impacts of the uncertainty in climate change were higher for loamy sandy soil than for sandy soils due to generally higher yield levels for loamy sandy soils. There were large differences between soil types in response to climate change, illustrating the importance of including soil information for regional studies of climate change impacts on cropping systems.

Effect of temperature and precipitation on nitrate leaching from organic cereal cropping systems in Denmark

“…The climatic effects highlighted in this study are in accordance with model-based studies of climate change impacts on N leaching from cereal cropping systems in Denmark (Børgesen and Olesen, 2011;Patil et al, 2012). For instance, Patil et al (2012), using the FASSET model to evaluate the sensitivity of winter wheat yield and soil N losses to stepwise changes in mean and variance of climatic variables in Denmark, showed an increase in mineral N leaching from winter wheat with increasing temperature, in particular for sandy loam soil at temperature increases above 2 • C. They also found higher simulated soil mineral N concentrations after crop harvest in summer and, therefore, higher risk of NO 3 N leaching during autumn and winter, which was ascribed to less N uptake by the crop and increased mineral N in soil profiles.…”

“…With increased temperatures, soil organic matter turnover increases and this potentially increases available soil mineral N, thus amplifying the risk of N leaching (Børgesen and Olesen, 2011). Moreover, we believe that changes in air temperature will also involve changes in planting and harvesting times as well as in fertilization rates and strategies (Doltra et al, 2014), which will also affect nitrate leaching.…”

Temperature and precipitation effects on wheat yield across a European transect: a crop model ensemble analysis using impact response surfaces

“…Other aspects that would need to be taken into account if making projections of yield impacts under climate change, such as the effect of increasing atmospheric CO 2 concentration, are deliberately not included in the analysis. IRSs have been applied in previous sensitivity studies of climate change impacts on permafrost (Fronzek et al 2011), hydrology (Hanasaki et al 2007, Wetterhall et al 2011) and crop yield (Luo et al 2007, Børgesen & Olesen 2011. The approach was found to be effective for the visualisation and rapid evaluation of model sensitivities across a wide range of combinations of climate changes that are not specific to individual projections from climate models.…”

“…Of the few systematic sensitivity studies that have been conducted, most focus on changes in average (mean or median) yields (e.g. Børgesen & Olesen 2011, whereas an additional key consideration for farmers is the reliability of the harvest from year to year, which is addressed in only a few studies (Luo et al 2007, Challinor et al 2010, Iizumi et al 2011.…”

“…The approach was found to be effective for the visualisation and rapid evaluation of model sensitivities across a wide range of combinations of climate changes that are not specific to individual projections from climate models. Further, in combination with projections of climate variables represented probabilistically, the approach can be applied to estimate the likelihood of exceeding a given impact threshold, such as a critical level of yield (Børgesen & Olesen 2011).…”