|Rotz, Clarence - Al|
Submitted to: Agricultural Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2007
Publication Date: 5/15/2007
Citation: Corson, M.S., Rotz, C.A., Skinner, R.H., Sanderson, M.A. 2007. Adaptation and evaluation of the integrated farm system model to simulate temperate multiple-species pastures. Agricultural Systems. 94(2):502-508. Interpretive Summary: Many dairy or beef producers in the northeastern US graze their cattle on pasture but rely on just one of several grass species to provide forage. Recent field research has shown that mixtures of more than one forage species -- a grass plus a nitrogen-fixing legume, for example -- often can improve the yields or lessen the environmental impacts of pastures. Computer simulation provides a tool to predict the effects of multiple-species pastures under a wide variety of management strategies and weather conditions. A whole-farm simulation model was modified to allow prediction of multiple-species pastures. This model will help its users estimate the effects of multiple-species pastures on environmental impacts and profitability of Northeastern dairy or beef farms.
Technical Abstract: Whole-farm simulation provides a tool for predicting the effects of farm management strategies on farm productivity and profitability. One such model, the Integrated Farm System Model (IFSM), was modified to allow representation of up to four forage species coexisting in a pasture mixture. The model was calibrated to simulate net herbage accumulation (NHA) observed during six periods of a 2002 experiment in a 3-species pasture in Pennsylvania composed of orchardgrass (Dactylis glomerata L.), white clover (Trifolium repens L.), and chicory (Cichorium intybus L.). Sensitivity analysis showed that predictions of NHA were most sensitive to both chicory and orchardgrass partitioning of photosynthate to shoot and specific leaf area, as well as chicory photosynthetic efficiency. The model was evaluated against 2003 data of NHA, crude protein (CP), and neutral detergent fiber (NDF) obtained from the same experiment. The model usually predicted CP within +/-2%, NDF within +/-19%, and period-specific NHA within +/-37%, underestimating total annual NHA by 19%. Given the generality and realism required of IFSM, the degree of precision in the modified pasture submodel seems acceptable for achieving IFSM’s primary goal of comparing the effects of different management scenarios on divergent farm types over many years of weather.