TheImprovement ofTropical and Subtropical Rangelands

182 IMPROVEMENT OF TROPIOAL AND SUBTROPIOAL RANGELANDS
spp. through aerial seeding. Initially, S. laumiliB and superphosphates
were distributed shortly before the rainy season over roughly plowed
seed beds, from which all timber had been mechanically cleared,
windrowed, and burned. In 1974, S. Ia.mw was superseded by S.
laamata (Verano), as the latter ~ reeiatant to anthracnose (Colletotrielaum
gloeoqorioides), as well as being more productive and
competitive. S. le.hr. (Seca) was mixed with the Verano eeed at
a ratio of 1 kg to 3.5 kg, as Seca is better adapted to areas of the
pasture with heavier soils. The stylo seed was not treated, and hard
seeds were broken down through natural weathering.
From 1973 onwards, efforts were made to reduce coetI of establishment
by eliminating capital-intensive clearing operatioDl, and
aerially sowing into open savannah with no prior treatment other
than burning or heavy grazing just before sowing. Plowing was eliminated
after clearing the II&vannahs in 197~1976, and the stylo seed
and superphosphate rates were reduced from 1977 onwards. All of
the methods have resulted in atylo-dominant Pastures, but the times
required to reach dominance have varied: 1 year on cleared and cultivated
areasj 2 years on uncleared areas at high rates of seed and
superphosphatej and 3 years when only 1 kg per hectare ofseed and
60 kg per hectare of superphosphate were spread.
Heavy grazing (more than one animal unit per 2 hectare) immediately
after lOwing is essential for obtaining good establishment of
stylo. Cattle selectively graze native gruaes in preference to stylo
during the first 2-3 months of the growing season, and this greatly
increases the competitive ability of the stylo seedlings when compared
with lightly grazed or ungrazed situatioDl. Stylo dominance
in the pasture increases with increased stocking rates. In Australia,
improved pastures carry about 10 times more cattle than native
pastures. (Edye and Gillard, 1984)
REfERENCES
Abernathy, G. H. and C. H. Herbel. 1973. Bnuh eradicatin" buin piUin"
and Hedinl machine for arid to ..miarid ranpland. JoVl'fllll 0/ Rant.
MfJnGI.mmt 26:189-192.
Alvares-Cordero, E. and C. M. McKell. 1979. Stem cuninc propacation of
big lacebrulh (Art.miM tridentata Nun.). JoVl'fllll 0/ &tag. MfJnGIcmmt
32:141-143.
Ansona Interacency Ran,e Committee. 1977. 7Yac U" o/Firt on Ariama
Ran,clandl, C. F. Pace and C. E. Granfelt, Coord. Publication 4, Forest
Service, U.S. Department of Agriculture, Fort Collins, Colorado, USA.