Limited response to phosphorus fertilization in native South American grasslands across a productivity gradient despite low phosphorus concentrations in grassland herbage.

ABSTRACT.- Background and aims:Since 1750, the species-rich grasslands native to the Río de la Plata basin in southern South America have sustained low-input livestock production. Typically, these grasslands have low herbage phosphorus (P) concentration, and P deficiency in livestock is not rare. Worldwide, P fertilization is used to increase the productivity and nutritive value of grasslands, but it is unknown whether the Río de la Plata grasslands are limited by P availability.