Submitted to: Soil and Water Conservation Society Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 7/20/2006
Publication Date: 10/13/2006
Citation: Garcia, A., Veith, T.L., Rotz, C.A., Kleinman, P.J. 2006. Comparison of Plot Studies and Farm Simulations for Different Manure Management Strategies [abstract]. Soil and Water Conservation Society Proceedings. p. 27. Interpretive Summary: An interpretive summary is not required.
Technical Abstract: The USDA-NRCS Conservation Effects Assessment Project (CEAP) calls for evaluation of current and novel agricultural management procedures with regard to both environmental and economical effectiveness. As agricultural management decisions are ultimately made and implemented by the producers, it is appropriate to assess effectiveness at the farm-scale. Whole-farm models, such as the Integrated Farm Systems Model (IFSM) are valuable in assessing environmental impact. In particular, IFSM is a continuous model capable of simulating the influence of management practices on nitrogen and phosphorous accumulation and loss to the environment while accounting for production changes and economic impact. However, due to the numerous sources of variation within a natural system, controlled research to quantify environmental effectiveness of management practices is often confined to single-event studies at the field- or plot-scale. This paper explores the validity of comparing management practice impacts measured in plot-level studies to those obtained using a whole farm model, such as IFSM. Our premise is that the whole farm model can quantify realistic environmental impact at the hands of the producer. In addition, the whole farm model readily provides production and economic information necessary for making sustainable management decisions. The comparison framework includes determining appropriate scaling techniques that enable validation and proper interpretation of IFSM's whole farm predictions based on plot-level observations. These scaling techniques must be spatial, up-scaling physical characteristics of 2m x 1m plots to whole farms; temporal, permitting comparison of discrete observations with continuous simulations; and management-based, relating field- and farm-size management processes with plot-sized treatments. The chosen comparisons estimate the impact of manure management strategies on phosphorous surface transport. The following manure management scenarios were simulated: surface manure application, manure incorporation, and three application rates. Normalized concentrations of simulated soluble phosphorous in runoff and sediment-bound phosphorous were compared to observed plot-study results. Soluble and sediment-bound particulate phosphorous reduction trends in surface runoff were similar between observed and simulated results for given changes in manure management. The study demonstrates the importance of plot-studies in validating and improving farm-scale modeling efforts. It also highlights limitations of expanding plot-level conclusions to larger scales. By using measured data to strengthen confidence in IFSM's ability to represent the environmental impact of various manure management practices, we are increasing the tools available to extension agents and producers to easily and more accurately assess both environmental and economic effects of the conservation practices they recommend and choose.