Are soybean yields getting a free ride from climate change?

Abstract

Soybean yields are often indicated as an interesting case of climate change mitigation due to the beneficial effects of CO₂ fertilization. In this paper we econometrically study this effect using a time series model of yields in a multivariate framework for a main producer and exporter of this commodity, Argentina. We have to deal with the trending behavior of crop yields trying to identify which variables are the long-run determinants responsible of the observed trend in soybean yields. With this aim we adopt a partial system approach to estimate subsets of relationships due to climate, technological and economic factors. Using an automatic selection algorithm we evaluate encompassing of the different equilibrium correction models. We have found that only technological innovations due to new crop practices and the use of modified seeds explain soybean yield in the long run. Regarding short run determinants we have found positive effects associated with the use of standard fertilizers and also from changes in atmospheric CO₂ concentration which would suggest a mitigation effect from global warming. However, we have also found negative climate effects from periods of droughts associated with La Niña episodes, high temperatures and extreme rainfall events during the growing season of the plant.