Environmental impact assessment of tractor guidance systems based on pasture management scenarios

Authors: Ashworth, Amanda; PUTMAN, BEN - University Of Arkansas; Kharel, Tulsi; THOMA, GREG - University Of Arkansas; SHEW, AARRON - University Of Arkansas; POPP, MICHAEL - University Of Arkansas; Owens, Phillip

Submitted to: Journal of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2022
Publication Date: 5/26/2022
Citation: Ashworth, A.J., Putman, B., Kharel, T.P., Thoma, G., Shew, A., Popp, M., Owens, P.R. 2022. Environmental impact assessment of tractor guidance systems based on pasture management scenarios. Journal of the ASABE. 65(3):645-653. https://doi.org/10.13031/ja.14930.
DOI: https://doi.org/10.13031/ja.14930

Interpretive Summary: Tractor guidance (TG) is a precision agriculture tool that enables more spatially precise applications of seed, fertilizer, and agrochemicals when compared to field operations conducted without global positioning system (GPS) guidance. In-depth field studies and subsequent environmental analyses are lacking but necessary for identifying TG environmental outcomes, prior to best management practice designation. Further, the majority of TG adoption has occurred on large-to-mid sized row crop farms with TG adoption among small-scale forage and cattle producers being largely non-existent, with research on its environmental enumeration is needed. Therefore, researchers set out to assess the environmental consequences of pasture management with and without the use of TG. This study combines experimental data collected during field trials on pasture systems with environmental assessments to quantify the potential environmental costs and benefits of performing pasture management operations, and to evaluate these effects for an average year of pasture management with and without TG. Researchers found that TG reduced the amount of areas in the field that had overlaps and gaps during herbicide and fertilizer applications. Overall, this study found that TG resulted in 8-12% fewer environmental impacts across all impact categories relative to non-GPS enabled technologies, although yield improvements under TG were crucial for enhanced environmental outcomes. Therefore, precision agriculture tools like TG may improve environmental sustainability, even in pasture systems that are not currently adopting these technologies.

Technical Abstract: The use of auto-guidance on tractors and self-propelled machinery helps to improve agricultural production efficiencies by reportedly avoiding negative environmental impacts from over-applying fertilizers and herbicides. Although, environmental impacts from auto-tractor guidance systems have not been systematically quantified and are difficult to assess at the systems-level. Therefore, this study uses a life cycle assessment (LCA) to quantify environmental impacts of employing tractor guidance (TG) over a range of fertility rates, sources (organic and inorganic), equipment, and pasture crops through scenarios based on in-field data (collected with and without TG). The use of TG reduced gaps by 7.6% and 10.1% and reduced overlaps by 32.5% and 4.2% during herbicide and fertilizer application, respectively. Estimated production gains with TG-on ranged from 2.7 to 6.5% over the baseline (TG-off), however, tractor fuel consumption increased when TG was employed. There was high uncertainty for productivity gain estimates, however, under scenario testing with an assumed 15% yield gain, TG resulted in 8-12% reduced environmental impacts across all impact categories relative to non-GPS enabled technologies. Yield gains are therefore crucial for pasture-based system sustainability when using TG, and TG results in less overlaps and gaps across pasture landscapes. Consequently, more targeted applications of inputs during production may lead to fewer nutrients in water systems, more sustainable production of food, and assumedly greater producer profitability.