Effects of Three Grassland Intensification Practices on Forage Production and Its Temporal Variability

Abstract

Grassland intensification practices including, overseeding with exotic species and P fertilisation (hereafter ‘overseeding’), the replacement of natural grasslands by sowing perennial pastures (‘perennial pasture’) and the replacement of natural grassland by winter–spring forage crop (‘forage crop’), are widely used to enhance production in livestock systems. Most studies have evaluated the effects of these practices on forage production in ungrazed experimental plots using non-comparable protocols. To our knowledge, few studies have jointly assessed the effect of different intensification practices on forage production and its variability under a standardised protocol across grazed commercial paddocks. We evaluated the effect of these three intensification practices on forage production across 45 commercial farms located in the temperate grasslands of Uruguay. We quantified the mean annual Enhanced Vegetation Index (EVI), a proxy for forage production and its inter- and intra-annual variability. We compared grazed paired paddocks, consisting of a natural grassland and one of the three intensification practices, and expressed the effect of each practice relative to natural grassland. Mean annual EVI increased by 2% with overseeding, 3% with perennial pasture and 9% with forage crop. Inter-annual variability increased by 6% with overseeding, 19% with perennial pasture and 24% with forage crop. Intra-annual variability increased by 8% with overseeding and 22% with perennial pasture. In summary, forage production increased slightly under all intensification practices and variability increased more markedly. These findings highlight that while forage production can be enhanced by intensification, increased temporal variability may represent a challenge under future scenarios of more frequent extreme climatic events.