In NOcsPS cropping systems, the abandonment of csPPP is likely to lead to lower yield levels and, more critically, increased yield variability due to uncontrollable biotic stress. Additionally, due to climate change, extreme weather events—such as drought, heat waves, frost, and waterlogging—are expected to become more frequent and intense. These factors will further reduce both yield stability and crop quality. However, empirical evidence on the interaction of biotic and abiotic stress, their spatiotemporal dynamics and their influence on yields and in particular NUE is still lacking. Since fertilizer production and nitrous oxide emissions are responsible for around three-quarters of the total greenhouse gases from cereal production (Feike et al., 2020; Riedesel et al., 2022), this is also highly relevant for improving the climate change mitigation potential of NOcsPS systems. In this regard, resistant varieties are an important key to securing yields and resource use efficiency as well as low emissions in NOcsPS systems.

The aim of this research project is to evaluate the individual and interactive effects of biotic and abiotic stress in NOcsPS cropping systems in a changing climate throughout Germany and to identify NOcsPS favorable regions in order to support the exploitation of the potential of NOcsPS as a sustainable cropping system.

More specifically we will evaluate the following hypotheses:

• Effects of biotic and abiotic stressors on crop yields are not fully additive
• Variability in stress impacts is driven by differences in crops, pathogens, environmental factors, and geographic regions
• Incorporating resistant crop varieties enhances yield stability and environmental sustainability in NOcsPS systems
• Climate change amplifies the interaction between biotic and abiotic stress, increasing challenges for NOcsPS systems

The work is divided into four different work packages:

WP1: Spatiotemporal assessment of yield loss, NUE and GHG emissions due to biotic stress in five cereal crops

German-wide long-term data on disease occurrence caused by fungal pathogens in relevant cereals will be used to assess the spatiotemporal dynamics of yield losses and the effects on nitrogen use efficiency and greenhouse gas emissions due to biotic stress. Different spatial aggregation levels will be employed in the analysis (e.g., large-scale agricultural regions, soil-climate zones, etc.), allowing the identification of favorable or unfavorable regions for NOcsPS cropping systems.

WP2: Evaluate individual and combined effects of biotic and abiotic stress on yields, NUE and GHG emissions in NOcsPS cereal cropping systems

Using dynamic weather indices (WI), the yield losses and effects on nitrogen use efficiency and GHG emissions due to abiotic stress (heat, drought, waterlogging, heavy rainfall, frost, etc.) will be assessed. The analyses will compare fungicide-free and fungicide-treated variants over the past decades, using relevant diseases and abiotic stressors (WI) as covariates in mixed models. The focus will be on how biotic and abiotic stressors influence outcomes individually, sequentially, or through additive or multiplicative interactions.

WP3: Crop resistance as a key to yield security, N-use efficiency and climate change mitigation in NOcsPS cropping systems

Using mixed models, the infestation-yield loss relationships for three variety types (susceptible, intermediate, and resistant) will be described for each crop species × disease combination. The models will be applied to historical infestation data, and the spatiotemporal analyses in WP1 & WP2) will be extended to include the aspect of variety resistance, implemented for the three variety types. The contribution of variety resistance to securing yield, nitrogen use efficiency, and the carbon footprint will be assessed nationwide in comparison with conventional farming.

WP4: Assessment of biotic × abiotic stress effects in NOcsPS systems under climate change

Nationwide daily weather data from the climate scenarios of the DWD core ensemble will be used to assess changes in the occurrence of biotic and abiotic stress under climate change (1971–2099). All relevant weather indices (WI) from WP2 will be calculated nationwide for this purpose. Additionally, infestation risk models will be employed to assess infestation risk under future climate scenarios. The corresponding covariates for biotic and abiotic stress will be incorporated into mixed models to assess the changes in biotic and abiotic stress effects on yields, NUE, and GHG emissions in NOcsPS systems under climate change.