In NOcsPS cropping systems the abandonment of csPPP is likely to result in lower yield levels and especially increased yield variability. Crop simulation models allow to complement the limited data on crop losses to pest and upscale it. Additionally, they enable testing and evaluating scenarios for future and/or altered climatic, technological or cropping systems related conditions, e.g., NOcsPS conditions.

Process-based crop models like DSSAT-CROPSIM simulate the soil-plant-atmosphere-system, while they consider abiotic stress due to water and nutrient deficiency. For the robust integration of biotic stress a sufficient empirical experimental data base is required for crop model calibration and validation and the parameterization of specific pests and their yield (loss) effects.

The aim of this subproject is the spatiotemporal assessment of yield level and variability of winter wheat in NOcsPS cropping systems compared to conventional systems as well as NOcsPS using precision sowing. Additionally, changes in Nitrogen use efficiency (NUE) in NOcsPS cropping systems will be assessed.

It is expected that temporal yield variability as well as spatial differences increase significantly under NOcsPS. Yield variability and hence Nitrogen uptake variability result in reduced NUE and increased risk of N-leaching. Possible adaptations of the cropping system (precision sowing, cultivar choice, etc.) help to reduce yield variability; however variability is still significantly higher compared to conventional production. The adaptation options can be evaluated regarding their effectiveness for yield stabilization.

The project is divided into 3 work packages:

Work Program WP 1: Integration of damage mechanisms of relevant pests into DSSAT-CROPSIM
Building on an extensive field experiment data base (>200 site-years, csPS vs. NOcsPS bzw. No fungi vs. fungi) the crop model CROPSIM will be calibrated and validated to simulate the damage mechanisms of relevant pests.

Work Program WP 2: Assessment of yield level and yield variability in NOcsPS vs. conventional
The validated model is now applied to simulate the effects of abandonment of csPPP in virtual experiments. Simulation runs can be conducted for longer time series (e.g., 1990-2018) for both NOcsPS experiment sites as well as a variety of additional sites from different cropping regions.

Work Program WP 3: Effect of cultivar choice and precision sowing on yield level and variability
The impact of cultivar choice will be simulated in the model by considering differences in phenology and resistance to specific pests. The simulation of cultivar effects builds on a large database of cultivar trials and the AWECOS project.

Expected Results: The results of this project enable findings on the effects of NOcsPS as well as fertilizer strategies and stand formation (e.g. equidistant row spacing) on abundance, diversity and function of predatory flies and their prey organisms in winter wheat cropping systems. This pest-predator-relationship serves as indicator of possible changes in the functional biodiversity inside NOcsPS cropping systems.