Paper Reviewed
Carvalho, J.M., Barreto, R.F., Prado, R.M., Habermann, E., Martinez, C.A. and Branco, R.B.F. 2020. Elevated [CO2] and warming increase the macronutrient use efficiency and biomass of Stylosanthes capitate Vogel under field conditions. Journal of Agronomy and Crop Science 206: 597-606.

Pastures remain a major food source for livestock in many regions, especially in rain-fed locations throughout tropical and subtropical zones. So it is of no surprise that there have been a number of studies examining the potential impacts of climate change on pasture species. The latest to do so comes from Carvalho et al. (2020). As their contribution to this subject, the team of six Brazilian researchers evaluated "the nutrient content, nutrient accumulation, nutrient use efficiency and growth of Stylosanthes capitata exposed to elevated CO2 and temperature under field conditions." S. capitata is a widely cultivated C3 pasture species of "high nutritional value, digestibility and high seed yield" that is also "considered resistant against drought and diseases, adapting well to low-fertility and acid soils."

The field study was conducted at the Ribeirão Preto Campus of the University of São Paulo (São Paulo, Brazil) during the late autumn/early winter season. Treatments included two atmospheric CO2 levels (ambient and ambient plus 200 ppm) and two temperatures (ambient and ambient plus 2°C). CO2 enrichment was applied using the FACE design during daylight hours only and warming was achieved using infrared heaters.

The results of the study revealed that warming along induced "no effects on macronutrient content, but increased the accumulation of nitrogen, potassium, calcium, magnesium and Sulphur, the nutrient use efficiency and root dry mass." In contrast, elevated CO2 alone "had no effect on most of the parameters evaluated." However, when combined, elevated CO2 and warming "improved the nutrient accumulation, nutrient use efficiency and whole-plant growth more than under isolated conditions of elevated CO2 or warming."

Commenting on these observations, Carvalho et al. write that the increased nutrient use efficiency and dry mass gain observed in the combined temperature and CO2 treatment "suggests that these plants may have increased productivity in the future of climate change without requiring increased fertilizer rates currently applied" (emphasis added). And that, of course, would represent a significant savings in time and money to achieve the same or greater S. capitata production without fertilizer application.