Principles of Soil Management in Neotropical Savannas - Principles of Sustainable Soil Management in Agroecosystems - page 60

Cerrado region supplies more than a third of Brazil's grain and cattle production and
>90% of cotton ( Gossypium herbaceum L.) and wood charcoal (Resck et al. 2008).
The relatively sparse population of the Cerrado, higher only than that in the Amazon,
not only demonstrates its short settling time but also the high productivities achieved,
critical to feed Brazil's mostly urban population and also a large export market.
Thus, neotropical savannas are important biomes for which a large, multifaceted
research has been conducted in many countries and institutions. With the focus of
this volume being on soil management, the objective of this chapter is to discuss the
Brazilian Cerrado, its principal soils, land use systems, potential and challenges, and
the effects of its ever-increasing importance to global agriculture and food markets.
3.1.1 M ain S oilS of the C errado and S oil f orMation f aCtorS
Land use and soil management systems in the Cerrado are primarily determined
by soil type and topography, not only due to their obvious influence on mechaniza-
tion, fertilization, and irrigation practices, but also because soil and relief themselves
result from other important environmental controls. It is out of the scope of this
chapter to provide a thorough review of soil genetic processes in the Cerrado, but
some important aspects are pertinent to be discussed prior to describing the major
soil types. The physical environment of the Cerrado and its control on soil genesis
and properties can be briefly described by means of the five state factors of soil for-
mation (Jenny 1941).
The most important soil parent materials would be deceptively easy to predict
because the Cerrado occupies most of the Brazilian Shield, composed of the Archean
and Proterozoic (>540 M years B.P., often >1 billion years) granites and gneisses.
However, this shield is covered by thick (>1000 m depth in some areas), extensive
Proterozoic marine sediments, often metamorphosed as shale and quartzite, and, to
a lesser degree, by limestone. Recently, deposited sediments of variable texture are
also common, more notably on the São Francisco river basin, and “lateritic” covers
are also widespread. There are significant areas covered by Cretaceous (145-65 M
years B.P.) basalt flows (especially in the Paraná river basin), mafic intrusions, and, to
a lesser degree, ultramafic rocks. The disparate nature of these parent rocks strongly
determines soil depth, mineralogy, texture, and fertility (Zinn et al. 2007a), which
are discussed in detail for each of the principal soil types. However, it is important
to note that most parent rocks are poor in nutrient cations and phosphate, and even
basalts and limestones are often highly weathered, thus resulting in a majority of
Cerrado soils being inherently nutrient-poor and acidic.
Time of soil formation is seldom accounted for in neotropical savannas, since
most of this biome is characterized by soils developed from very old rocks. However,
its importance is vividly expressed in special cases, such as in some recent fluvial
deposits, or on freshly denuded erosional surfaces. Nonetheless, due to the pre-
weathered nature of most parent rocks, the time state factor most often controls only
soil depth and horizonation, with little effect on inherent soil fertility except for shal-
low eutrophic soils developed over recently exposed limestones and basalts.
Topography exerts a major regional control through climate: ~73% of the Cerrado
area occurs between altitudes of 300 and 1100 m, with 22% below 300 m (Adámoli