Integrating crop and dairy production systems: Exploring different strategies to achieve environmental targets.

The integration between crop and livestock production systems (ICLS) at regional level is seen as a pathway for more sustainable food production. The objective was to assess the effects on farm structure, economic performance and environmental impact of an ICLS with varying constraints on agricultural emissions, changes in land use and a lower external input use as means to achieve environmental targets. A linear optimization model was used for economic optimization of ICLS under different scenarios for the case of crop and dairy production systems on sandy soils in the Netherlands. The model was combined with a farm nutrient balance and life-cycle assessment to determine the impact on nutrient surpluses and greenhouse gas (GHG) emissions. Environmental costs for society were calculated based on available prices for GHG emissions and nutrient surpluses. As a reference, specialized crop and livestock systems without integration were optimized. An economically driven ICLS under current Dutch policy without additional constraints was modelled. This strategy was economically interesting and increased gross margins, but the environmental costs for society were higher when compared to the reference systems without integration. Thereafter, four scenarios were modelled representing varying constraints as a means to achieve environmental targets. These scenarios were hypothesized to lower the environmental costs for society by targeting a reduction in agricultural emissions, lower external input use or changes in land use. Stricter constraints on greenhouse gas (i.e., a reduction of at least 30%) and ammonia (i.e., a reduction of at least 37%) emissions and de-intensification strategies (e.g., lower milk production per cow, reduced concentrate intake per cow and lower mineral N fertilizer use in the dairy sub-system) reduced gross margins of the ICLS up to €34,395 yr. Furthermore, it resulted in a substantial reduction in the gross margin for the dairy sub-system, while gross margins for the crop sub-system substantially increased. However, these scenarios reduced environmental impacts and associated costs for society substantially up to €60,045 yr. For a scenario with land use constraints (i.e., stricter constraints on area proportions for potatoes and sugar beets and an increase in the area used for permanent grassland) there were still economic benefits while there was also reduction in the environmental costs of production. The results help to further design and assess the potential contribution of ICLS to improve the sustainability of the current farming system.