Sustainable grazing strategies for semi-arid rangelands of central Argentina

DISTEL, R.A.

Sede Boqer, Israel

Conferencia; Second Drylands, Deserts and Desertification Conference; 2008

Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev

The central-east part of Argentina (36-40’ S 62-66° W) is occupied by rangelands, which cover an area of 10 million ha. Climate is temperate-semiarid. Mean annual temperature is 15°C, and mean annual precipitation 400 mm (30% interannual coefficient of variation). Fire has been a natural phenomenon in these rangelands. Soils are sandy-loamy. Potential vegetation physiognomy is open shrubland. Dominant woody species are Prosopis caldenia, P. flexuosa, Larrea divaricata, Condalia microphilla and Chuquiraga erinacea, whereas dominant herbaceous species are Poa ligularis, Stipa clarazii, S. tenuis, and Piptochaetium napostaense. Before European colonization, large herbivores were scarce. Since colonization, the area has been grazed by sheep and cattle. Presently, rangelands are in regular or poor condition. Overstocking, interacting with drought and fire exclusion is considered the main cause of deterioration. Rangeland deterioration is evidenced in the replacement of palatable grasses by unpalatable grasses or annual species, increases in woody species density, bare soil formation, loss of soil, reduced forage productivity, and reduced carrying capacity. Recovery of these rangelands requires proper management of stocking rate, grazing, and fire. A sound strategy would be to adjust stocking rate of breeding herds to the carrying capacity for a semi-drought year (precipitation around 20-30% below the annual mean). The excess of forage in normal or wet years could be used to fatten culled animals, for growing stockers, or it could be used as fuel for burning. Continuous grazing should be replaced by rotational grazing, to allow palatable grasses to recover from defoliation through appropriate rest and to improve the spatial utilization of rangelands. Since unpalatable grasses and woody species appear to be more sensitive to fire than palatable grasses, prescribed burning could be used for controlling undesirable species. These strategies, in combination with proper management of breeding cows, are being applied on a private ranch (3,400 ha) since 1999. Results showed increases in weaning percentage (from -60 to 80%) and meat production (from —12 to 20 kg meat ha-1 year-1), and improvements in rangeland condition.