Site specific impacts of climate change on crop rotations and their management in Brandenburg/Germany (2020.0)

Kersebaum K., Schulz S., Wallor E.

EGU2020-11783, (),

doi:10.5194/egusphere-egu2020-11783

Abstract

Climate change impact on crop production depends on the cultivated crop and its position within
crop rotations and on site conditions, e.g. soils and hydrology, buffering adverse weather
situations. We present a regional study across the federal state of Brandenburg/Germany based
on gridded climate data and a digital soil map using the HERMES-to-Go model. The aim was to
investigate defined crop rotations and common agricultural practices under current and future
climate conditions regarding productivity and environmental effects. Two contrasting GCMs (HAD
and MPI) were used to generate climate input for modelling for the RCPs 2.6 and 8.5.
5 different types of crop production were simulated by defining crop rotations over 4-5 years for
soil quality rating groups. While one rotation is comprised by the most common crops, another
rotation modifies the first one by introducing a legume followed by a more demanding crop. The
third rotation intends to produce higher value crops, e.g. potatoes than the first one, while the
fourth rotation has its focus on fodder grass and cereal production. Building on this the fifth
rotation replaces the fodder grass by alfalfa. All rotations are simulated in shifted phases to
ensure that each crop is simulated for each year.
Sowing, harvest and nitrogen fertilization were derived by algorithms based on soil and climate
information to allow self-adaptation to changing climate conditions. The crop rotations are
simulated under rainfed and irrigated conditions and with and without the implementation of
cover crops to prevent winter fallow.
We used the digital soil map 1:300.000 for Brandenburg with 99 soil map units. Within the soil
map unit, up to three dominant soil types were considered to achieve at least 65% coverage. 276
soil types are defined by their soil profiles including soil organic matter content and texture down
to 2 meters. Groundwater levels are estimated using the depth of reduction horizons as constant
values over the year, to consider capillary rise depending on soil texture and distance between the
root zone and the groundwater table.
In total each climate scenario contains about 148.000 simulations of 30 years. Beside crop yields
we analyse the outputs for trends in soil organic matter, groundwater recharge, nitrogen leaching
and the effect on water and nitrogen management using algorithms for automatic management.

Results indicate that spring crops were more negatively affected by climate change than winter
crops especially on soils with low water holding capacity. However, few areas with more loamy
soils and potential contribution of capillary rise from a shallow groundwater even benefited from
climate change. Irrigation in most cases improved crop yield especially for spring crops. However,
further analysis is required to assess if irrigation gains an economic benefit for all crop rotations.
Nitrogen leaching can be reduced by implementing winter cover crops. Soil organic matter is
assessed to decline for most sites and rotations. Only the rotations with multiyear grass or alfalfa
can keep the level, but not on all sites.