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

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Grasslands of the world
TABLE 5.9
Winter performance and yearly liveweight gain for two treatments on natural grassland .
Treatment
LWG winter
period
kg/day/head
1997
Year
1998
liveweight/ha/year
1999
P fertilization 0.615 151 219 267
P fertilization + over-seeding 0.695 173 245 302
tested and also seeding methods, previous grassland management , fertilization
levels, over-seeding, grazing management , etc. Rarely do the introduced species
persist for more than three years due to strong competition from native species.
Despite this, when some winter species become established, animal production
increases are large. Higher productivity has been obtained recently in a threeyear
grassland improvement trial. Preliminary results of two treatments are
shown in Table 5.9 (Pizzio, unpublished).
The most interesting results from this trial are the excellent animal performance
in winter , which exceeded 0.6 kg/day when normally there is no gain at this
season, and the year-on-year productivity increases.
This experiment considered some factors not previously evaluated:
(1) a higher level of phosphorus fertilization in comparison with previous
research, which brought the phosphorus content in grass above 0.22 percent,
which had not previously been recorded; (2) a sward structure that offered a
good quantity of green, easy-to-graze grass; and (3) a diverse and desirable
botanical composition , that offered good quality green feed in winter , with
species such as red clover , Lotus cv. Rincón, ryegrass and oats. These factors,
with others, allowed the animals to harvest a large quantity of high quality
of forage in the available grazing time, to attain performance similar to those
from sown pastures.
Legume introduction
The need to improve the primary production and quality of Uruguayan
grasslands led to legume introduction using minimum- or no-tillage techniques,
as a way to increase secondary production. Correcting soil P deficiencies is a
crucial element in this process (Bemhaja and Levratto, 1988; Berretta and
Formoso, 1993; Berretta and Risso, 1995; Risso and Berretta, 1997; Bemhaja,
1998). The study of anthropogenic factors provides an understanding of
various aspects of induced vegetation succession, which contributes to success
in the application of the technology. To make a proper improvement in natural
grasslands, the following must be considered:
• Vegetation sward as botanical composition defines the quality of the grassland ,
related to productive types , vegetative types and growing cycle.
• Soil type , topography, stoniness, drought and erosion risks, drainage, etc.
• Grazing objective for the improved paddock: cattle , sheep , fattening,
weaning, etc.