Agent-based modelling applied to nitrogen and phosphorus assessment in agroecosystems

In Uruguay, dairy production is essential for the country and is under scrutiny due to the environmental impacts it can cause. Impacts are primarily the result of inefficient management practices which lead to an excessive use of nutrients —mainly nitrogen (N) and phosphorus (P)— and their surplus flow into the environment, affecting soil, groundwater, and rivers. In this context, this paper explains research that has generated new knowledge for Uruguay's dairy sector to achieve more sustainable production by understanding which farm management practices maximize nutrient efficiency while reducing environmental damage. The research used a multi-methodology approach for the case study of a typical Uruguayan dairy farm by applying the Nutrient Budget Method and developing an Agent-Based Model (ABM) called Nitrogen Phosphorus Management (NPM). Nutrient budgeting is a valuable and straightforward method for analyzing farm data and evaluating all the nutrient inputs and outputs. However, it has some visual and research limitations that can be complemented with suitable agent-based modeling. The ABM modeling approach enables the analysis of the model’s agents in space and time, capturing the agroecosystem’s heterogeneity. Through their combined application, the research results demonstrate that, along with the use of correct management practices, it is possible to improve nutrient efficiency, and, in this way, dairy production systems can be less dependent on external nutrient inputs. The main findings indicate that nitrogen biological fixation, pastoral diets, cow stocking rates, and phosphorus accumulation in soils are key management variables that affect nutrient efficiency and environmental impacts.