Submitted to: ASAE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 7/17/2005
Publication Date: 7/17/2005
Citation: Gowda, P., Mulla, D.J. 2005. Environmental benefits of precision farming - A modeling case study. In: American Society of Agricultural Engineers Annual International Meeting Technical Papers, July 17-20, 2005, Tampa, Florida. Paper Number 051042. 2005 CDROM. Interpretive Summary: Precision agriculture is an approach that allows the rate of phosphorus fertilizer to a field to be varied in response to spatial pattern of soil P levels and soil pH. It is hypothesized that this approach maintains crop productivity while reducing the environmental impacts of fertilizers and increases farm profitability. However, this hypothesis has not been fully tested. This study compares predicted edge-of-the-field phosphorus losses with a variable rate versus a uniform P fertilizer application rate using a long-term climatic record. Results indicate that the variable rate application strategy could produce measurable reductions in off-site phosphorus losses on similar fields in comparison to a uniform application rate strategy.
Technical Abstract: In this study, we evaluated the environmental impacts of spatially variable versus uniform phosphorus fertilizer application rates on a 32-ha commercial corn field in Blue Earth County of southern Minnesota. In 1998, the phosphorus rates (0-39 kg/ha) were variably applied in accordance with measured surface soil pH and soil Bray P levels across 50 x 50 grid spacing. Surface runoff and tile drain leaching losses of sediment and phosphorus were measured using automated sampling systems. The Agricultural Drainage and Pesticide Transport (ADAPT) model was calibrated to measured water fluxes, and losses of sediment and phosphorus to surface waters. There was good agreement between measured and modeled water fluxes, sediment, and phosphorus losses. Using the calibrated model, a sensitivity analysis was conducted for both uniform and variable rate phosphorus application strategies using a 50-yr climatic record. Phosphorus losses for the variable strategy were significantly lower than losses for a uniform strategy.