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

The South American Campos ecosystem 199
frequent on heavily grazed treatments, whereas the caespitose species
Andropogon selloanus and Elionurus candidus were commoner on lightly and
very lightly grazed paddocks. Plant groups that are independent of growth
habit, such as Paspalum paucifolium , Eragrostis neesii and Eryngium ciliatum ,
occurred on drier sites, while Andropogon lateralis , Eryngium horridum ,
E. elegans , Schizachyrium microstachyum and Baccharis trimera occurred on
sites with higher soil moisture levels, and were also sensitive to heavy grazing
.
An interesting issue was the tolerance of heavy grazing shown by
Coelorachis selloana and Piptochaetium montevidense , both low growing
with buds close to the soil. However, when FO is higher they grow along
with the height of the sward profile and remain as contributors to DM
production. The ability to adapt growth habit is also seen in the native
legume Desmodium incanum : it remains prostrate under heavy grazing,
but its branches rise to sward height when grazing is reduced. The legumes
Aeschynomene falcata , Chamaecrista repens , Stylosanthes leiocarpa , Trifolium
polymorphum and Zornia reticulata are associated with higher utilization
intensities, but need resting periods. Non-limiting FO management practices
on natural grasslands seem to be an ecologically efficient procedure to restore
and maintain grassland productivity in a sustainable manner.
FERTILIZING CAMPOS GRASSLAND
Fertilization in Argentina
In the past 30 years the Mercedes Research Station has evaluated the effects
of fertilizing natural grasslands on animal production in the Rocky Outcrops
region. Large increases in stocking rate , liveweight gain per animal and
annual beef production per unit area have been registered in all trials. The
first study showed that, with NPK fertilization , animal production increases
yearly, reaching 210 kg LW/ha/year by the third year, which represented a
138 percent increase over the control (Royo Pallarés and Mufarrege, 1970).
Subsequently, different N levels were applied to natural grassland , which
raised animal production in the third year to 254 kg LW/ha/year at 120 kg N/
ha/year (Mufarrege, Royo Pallares and Ocampo, 1981).
Phosphorus fertilization was evaluated for 11 years at the Estancia Rincón
de Yeguas. Average animal production on fertilized paddocks was 40 percent
higher, for the three stocking rates evaluated, with production levels that
rose to 188 kg LW/ha/year (Benitez, unpublished). In another eight-year
fertilization and stocking rate trial by Mercedes Research Station, production
reached 176 kg LW/ha/year at the higher stocking rate. The increase in total
animal production at the same individual performance level was 76 percent
(Royo Pallarés et al., 1998). Observed effects of phosphorus fertilization on
grasslands are increased forage production, a large increase in the phosphorus
content of the forage and increased legume cover.