Environmental Impact Assessment of Tractor Guidance Systems Based on Pasture Management Scenarios

Abstract

HighlightsTractor guidance (TG) reduced the overlaps and gaps during fertilizer and herbicide applications.Production gains with TG on were 2.7% to 6.5% relative to TG off; however, fuel consumption increased.A 5% increase in yield is needed to make tractor guidance environmentally remunerating.Abstract. The use of auto-guidance on tractors and self-propelled machinery improves agricultural production efficiencies by reportedly avoiding negative environmental impacts from over-applying fertilizers and herbicides. Environmental impacts from auto-tractor guidance systems have not been systematically quantified and are difficult to assess at the farm system level. Therefore, this study uses a life cycle-based assessment to quantify the environmental impacts of deploying tractor guidance (TG) over a range of fertility rates, fertilizer 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 absolute 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% to 12% reduced environmental impacts across all impact categories relative to non-GPS enabled technologies. Future research should be focused on actual yield-based responses from TG, as well as field emissions, operator experience, and resulting water quality. Overall, yield gains were crucial for improved pasture-based system sustainability when using TG because TG results in fewer gaps and overlaps, thereby resulting in greater input use across pasture landscapes. Consequently, more targeted applications of inputs during production may lead to fewer nutrients in water systems and more sustainable production of food. Keywords: Auto-guidance, Forage systems, Life cycle assessment, Poultry litter, Precision agriculture, Small farms.