Grasslands of the World.pdf - Disasters and Conflicts - UNEP

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Plate 11.10b
A grassland dominated by Paspalum dilatatum . Winter (flooded) view.
Grasslands of the world
30 kg DM/ha/day in December and January. Scarce winter production is caused
by the depletion of cool-season grasses caused by continuous overgrazing of
domestic cattle after windmills and fences were introduced 100 years ago.
The dominance of warm-season grasses and loss of nitrogen fertility further
prevent the establishment of cool-season grasses every autumn . Low winter
productivity limits the carrying capacity and determines the production system
of the area: cow-calf operations. Almost 3.5 million cattle roam the 6 million
hectares of the Flooding Pampas , exporting 2 million calves annually to be
raised on pastures in cropland or feed yards. Annual secondary production
may be estimated at 90 kg/ha.
Winter productivity may be significantly increased by hard early autumn
grazing or herbicide spraying of the warm-season grasses, followed by nitrogen
fertilization . This promotes the establishment and growth of Lolium
multiflorum , an excellent quality exotic grass that thrives well in intermediate
communities . Phosphate fertilization may also increase cool-season grass production
by promoting the density of herbaceous legumes Lotus tenuifolius and
Trifolium repens that enrich soil nitrogen through fixation.
Cropland Pampas cultivated pastures
The most renowned Pampas is the sector extending in a circle around the
Flooding Pampas . Constituting the main cropping area of Argentina , with
77 percent of the cattle stock and 70 percent of the human population, it
contains the major cities and industrial development . The original tussock
grasslands are now rainfed croplands producing soybeans, maize, wheat
V. ALEJANDRO DEREGIBUS AND MARTIN F. GARBULSKY