Late Summer Intensive Grazing, an Alternative to Herbicide Application in Rangelands of the Flooding Pampa

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The Flooding Pampa harbors grasslands of high conservation value and provides grazing ground for extensive livestock production in uplands while lowlands are less productive. The Aboveground Net Primary Productivity (ANPP) of cool-season C3 grasses limits livestock production in this region. Consequently, two managements have been implemented to promote ANPP of these upland grasses, in contrast to the No Promotion (NP) traditional management with continuous stocking during the entire year: Herbicide Promotion (HP), and less commonly, Late Summer Intensive Grazing (LSIG). Here, we compare the effectiveness of LSIG as a potential alternative to herbicide application in promoting cool-season grass production and evaluate both short- and longer-term impacts on inter- and sub-annual ANPP. To this end, we integrated remotely sensed ANPP data from 2013 to 2019 with rainfall data from meteorological stations, field observations, and management information provided by farm managers. We found that in comparison to NP in uplands, both HP and LSIG successfully promoted ANPP during the cooler months (P < 0.05). However, under HP, this came at the expense of warm-season grasses and annual ANPP, to such an extent that upland annual ANPP under HP was reduced to similar values of the normally less productive lowlands. Our study showed that cool-season grasses can be successfully promoted with or without herbicide use, but HP leads to a longer-term degradation of forage resources. Contrary to HP, LSIG is a management that reconciles the dual goals of livestock production and grassland conservation in the Flooding Pampa.