This chapter explores SALUS (Systems Approach to Land Use Sustainability), a process-based crop model designed to simulate interactions between soil, climate, genetics and agronomic management, focusing on their effects on crop growth and yield, soil organic matter and nitrogen dynamics. SALUS explores how different components of an agricultural field system interact and influence plant growth and soil nutrient dynamics. A particular strength is its ability to simulate multiple years of a cropping system. The chapter explores how the model works in terms of: genetics; soil and carbon dynamics; and soil, weather, and agronomic data. The chapter includes three case studies showing the use of SALUS: to evaluate optimal locations for bioenergy crop implementation while quantifying both productivity and environmental impacts; to determine optimal variable rate fertilizer applications; and to assess the long-term impact of differing tillage practices across the US Midwest.