Online

Bondeson, Finn A.

Civil and Environmental Engineering

2023

M.S.

Improper management of agricultural nutrients can have negative impacts on ecological and human health, notably through facilitating eutrophication in surface water bodies used for drinking water and recreation. Various management strategies can improve the outcomes of agricultural nutrient management, but some face operational and logistical challenges. This thesis provides analysis of two tools that can help practitioners improve their nutrient management strategies: a technical tool comprising an aerated composting and heat capture system and a spatial analysis tool offering methods to predict phosphorus-leaching potential from agricultural land at the watershed scale. The first study herein evaluates nutrient status and financial and energy cost for a pair of commercial compost windrows with and without forced aeration at full scale in a normal production setting. Compost treated with a forced aeration and heat capture system was deemed suitable for market in approximately 25% less time than a conventional, straddle turned windrow. Analysis of nitrogen (N) and phosphorus (P) dynamics throughout the study suggested that forced aeration likely reduced fugitive N losses via volatilization and denitrification, and P loss via leaching. During the active composting process, operational costs for force-aerated compost were 2.1 times more expensive and 5.5 times more energy-intensive than a conventional compost per m3. However, the energy and infrastructure cost offsets provided by the aeration and heat capture system could provide a net savings of $1.51 m3 finished compost. The second study herein presents a set of methods to predict and visualize soil P saturation ratio (PSR) and P mass balance of agricultural parcels across a watershed. A K-means cluster analysis was performed to aggregate agricultural parcels by soil texture, average slope, and crop type. Using a set of parcels encompassing approximately 20% of the watershed's agricultural land with known soil test and nutrient management parameters, predictions of PSR and P balance status of agricultural land across the watershed were made by cluster. This resulted in an average PSR of 0.0399 ± 0.0002 and an average P balance of 5.50 ± 0.22 kg P ha-1 yr-1. Results were used to visualize areas with potentially high P release potential; such visualizations could assist practitioners in nutrient management decision making.