Agriculture Reference
In-Depth Information
under rototiller, manual hoeing, harrowing, and postemergence herbicide, and 35%
under preemergence herbicide. The use of agroforestry systems for coffee produc-
tion, still mostly experimental, may lead to higher soil quality for coffee production.
3.2.5 p
lantation
f
oreStS
Clearing the Cerrado vegetation for agriculture has always resulted in a variable
amount of dead tree stems that were mostly short (<15 m long) and so twisted that
they could not be used in sawmills. Using these stems and small woody residues
for charcoal production in rustic, earthen ovens was an obvious alternative, and this
became a common activity by landless workers, becoming widespread with large
land use conversion. After 1950, the demand for wood charcoal by large iron-and-
steel plants in Minas Gerais spiked, and it soon became obvious that the native
Cerrado vegetation could not meet the high demand. Thus, large-scale forest plan-
tations with fast-growing
Eucalyptus
spp. started spreading, supplying wood not
only for charcoal but also, more recently, for pulp-and-paper industries. Many small
plantations were also established for on-farm use as fences, fuelwood, and building
works. Large forest plantations with
Pinus
spp. also became common in some south-
ern Cerrado areas for diverse uses such as timber, resin, and pulp production. All
forest plantations in the Cerrado occupied 3.1 million ha in 2002 (Sano et al. 2010) or
about half of the total reforested area in Brazil. Although
Eucalyptus
and
Pinus
for-
ests are planted in every type of Cerrado soil, due to high land prices, they are gener-
ally established on marginal lands, that is, degraded pastures, eroded Haplustoxes,
unfertile Quartzipsamments, and sometimes, hilly or rocky areas. Other plantation
forests were initially poorly adapted to Cerrado conditions and thus had low yields,
but after decades of genetic improvement, these plantations are highly competitive
with other regions of Brazil, where
Eucalyptus
productivities are among the highest
in the world.
When not established on degraded pastures or croplands,
Eucalyptus
and
Pinus
stands are planted after clearance of native vegetation. Soil preparation typically
involves heavy harrowing of the entire area, but often only in the planting row, fol-
lowed by digging pits with shovels or hoes for the seedlings. Liming is not tradition-
ally done, and fertilization is mostly restricted to <1 Mg rock phosphate ha
-1
and
~100 kg ha
-1
of soluble P and NPK mixed in the pit, before and sometimes after
planting (Zinn et al. 2011). Weed control is done chemically or by hand or mechani-
cal hoes, but after the second year, most stands grow so high that shading precludes
weed growth. The management of
Eucalyptus
plantations depends on the industrial
purpose: plantations for charcoal are typically established with genetically heteroge-
neous, seed-produced trees, which are cut by age 6 to 7 years and allowed to sprout as
coppice stands, which are cut again after additional 6 to 7 years (Zinn et al. 2011), and
sometimes allowed to grow a third, low-production cycle. Conversely, plantations for
pulp and paper use highly selected, productive clone seedlings, which are cut at ages
5 to 7 years and replanted. Pine stands are typically formed only by seeds and use
much less fertilizers and inputs than
Eucalyptus
plantations; also, they are harvested
at ages 15 to 20 years and then replanted. For both species, pesticide use in the field is
generally low or null, as pests and diseases are prevented by resistance traits selected
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