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

The South American Campos ecosystem 205
of grasslands (Brougham, 1959; Parsons, Carrëre and Schwinning, 2000). For
Paspalum notatum , responses to N and FO were observed reaching LAI values
of 9.4, which is high for this kind of plant.
With low N, the pasture is more prostrate and less exposed to animal defoliation.
With increased FO , grazing is more selective, leaving more residues
that contribute to regrowth. With frequent grazing and low N there are smaller
leaves with low LAI values, less light interception and lower DM production.
Increasing N promotes faster LAI recovery, which in the higher FO promotes
a faster regrowth start, with higher LAI at the end of the regrowth period.
Therefore there is higher radiation interception, higher carbon sequestration ,
higher forage production and higher efficiency of applied N.
Green DM of the grassland is produced from the grazing stubble , which
increases according to the net AR of the regrowth period, which is increased by
the action of N. The effect of management has been well documented, because
Boggiano (2000) observed available DM increases of 1 000 kg/ha for each 35
days of regrowth, as this is the response to lighter grazing on fertilized grasslands.
The low LLS makes difficult to maintain high LAI values, while low FO ,
with low LAI , consistently show less leaf length and less final length. Higher
grazing intensity leads to reduced forage production, lower forage accessibility
for grazing animals and consequently lower intake.
In terms of plants and pastures, with low FO and poor N status, the priority
is to accumulate dry matter in stolons and roots, preserving meristems and
increasing the proportion of stolons in total aerial biomass, so as to supply the
demands of the next growth period. At intermediate FO, stolon biomass is maximal
and root biomass minimal. This topic requires more study. Stolons cannot
be grazed, so Paspalum notatum and its biological forms show greater cover on
grazed grassland . Defoliation and shading alter the carbon supply to plants and
increase the proportion used for leaf production, while factors that reduce meristem
activity (N, moisture) promote higher carbon accumulation in the roots
(Lemaire, 1997). Careful use of N increases the capacity of natural grasslands to
sequestrate carbon from the atmosphere, storing it in permanent plant structures
for growth, organ and tissue development , DM production, and consequently
livestock feeding. Better performance tends to reduce methane emissions and
the litter that, with animal dejections, constitute the main source for renovation
and increment of soil organic matter. This enrichment of the environment
promotes favourable conditions for microfauna, which form part of the fertility
chain of predator fauna, hence contributing to environmental health, nutrient
recycling and strengthening of life expression in natural grassland.
IMPROVEMENT TECHNIQUES
Over-seeding
This technique for introducing valuable forages to the sward has been
evaluated for a long time. Many forages, mainly winter legumes, have been