Trade-offs between agronomic yields and sustainability in winter wheat cropping systems under climate change mediated by soil organic matter content

Empirical data is key to anticipate the impact of future climatic conditions on cropping systems and develop land management strategies that are sustainable while ensuring food security. Here, the combined effects of projected increases in temperature, atmospheric CO2-concentrations, solar irradiation and altered precipitation patterns on winter wheat cropping systems were investigated using an Ecotron. Experimental plant-soil systems were subjected to three different meteorological conditions representing a gradient of ongoing climate change implementing the weather patterns of the years 2013, 2068, and 2085 respectively. In each climate, wheat plants were grown in soil monoliths from two differentially managed agricultural fields where one historically received twice as much organic matter (OM) as the other. Yields in the low-OM systems consistently increased across the three years and exceeded yields of the high-OM system notably in the future climates. Limited plant growth in the high-OM systems was possibly linked to increased nutrient immobilization in more complex belowground soil food webs and stronger plant-microbe competition. Moreover, modelling indicated lower CO2 and N2O-emissions for the low-OM systems in all climates, while reduced risk of nitrate leaching may make the high-OM systems more environmentally friendly. Together, these results support potential sustainability benefits of regenerative OM management, but also highlight areas of improvement, such as refinement of management practices to facilitate plant nutrient uptake and reduce greenhouse gas emissions. As shorter wheat growth cycles were observed in the future climates, one lever to replenish and mobilise soil nutrients and break disease cycles could be diversifying crop rotations and cover crops. Moreover, in both here studied soil types the wheat plants developed natural coping mechanisms against environmental stressors, such as enhanced root growth and increased levels of proline and silicon. Unravelling the molecular mechanisms that trigger such inherent plant defences is a further interesting target for breeding future crops.