Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 11, 2008
Publication Date: July 1, 2008
Citation: Garcia, A.M., Veith, T.L., Kleinman, P.J.A., Rotz, C.A., Saporito, L.S. 2008. Assessing manure management strategies through small-plot research and whole-farm modeling. Journal of Soil and Water Conservation. 63(4):204-211. Interpretive Summary: Manure management strategies are evaluated at the plot-scale but are implemented by producers at field and farm scales. Plot study data were used to test and improve the prediction of phosphorus loss due to manure application in a farm-level model. The model predicted less soluble phosphorus loss when broadcast manure was incorporated. This work can aid producers and decision-makers in comparing long term risks of whole-farm management strategies.
Technical Abstract: Whole-farm models, such as the Integrated Farm Systems Model (IFSM) are valuable in assessing environmental impacts and economic risks of management practice changes. However, due to the numerous sources of variation within the natural system, controlled research to quantify environmental effectiveness of management practices is often confined to lab- or plot-scale experimentation. The ramifications of incorporating event-based, plot-scale experimental information into a farm-scale model to investigate the impact of manure management strategies at field-level were investigated. Scenarios were established in IFSM to replicate a plot-scale experiment by Kleinman et al. (2006) as accurately and precisely as possible. Three dairy manure application methods (control, broadcast, and incorporated) were evaluated on two soils (low and high runoff potential) found in the Eastern Allegheny Plateau and Mountains region of Pennsylvania. Besides input of physical and climate data such as precipitation, soil properties, and land use cover; the curve number, an IFSM input, was back-calculated to match the water balance to the change in surface cover and roughness. Observed and simulated soluble and sediment-bound phosphorous loads and concentrations were compared visually and by percent change from the control condition. IFSM results were found to compare well visually to the experimental results with the low runoff soil replicating observed values more closely than the high runoff soil. Average annual environmental and economic risks for the farm were simulated for the same scenarios. Soluble phosphorus losses were found to decrease with manure incorporation by 50 and 80% for the low and high runoff soils respectively. However, net return also decreased by 11 and 5% respectively. This study provides quantitative results in an initial step to evaluate and up-scale plot-level information to the farm-scale, thus enabling more confidence in addressing the environmental risks of whole-farm nutrient management through "what-if" scenarios. This work suggests opportunities for future work in simulating the field-scale effects of tillage systems and other manure management technologies such as manure injection.