World’s Soil Resources

Figure 12.6 Expansion of the agricultural frontier under rainfed conditions in the north of Argentina. Source: Viglizzo & Jobbagy, 2010.
It has been estimated that agriculture in Argentina during the 20th century decreased soil carbon stocks by
27-50 percent. The causes included the turning over of grasslands and prairie soils rich in organic C with mould
board and disc ploughs, and the loss of crop diversity (Studdert, Echeverría and Casanovas, 1997; Viglizzo and
Jobbagy, 2010; Sainz Rozas, Echeverria and Angelini, 2011; Caride, Piñeiro and Paruelo, 2012; Milesi Delaye et
al., 2013). The potential of no-till farming to increase soil organic C stocks is still under discussion. In a review
of 42 no-till vs plough till data sets from field experiments conducted in the Pampean region, Steinbach and
Álvarez (2006) concluded that a 2.76 Mg ha -1 organic C increase was observed in no-till systems compared with
tilled systems, with a relatively higher increase of organic C in areas of low organic matter level. However,
Álvarez et al. (2009) observed no significant change in topsoil organic C content after adoption of continuous
no-till in previously conventionally tilled loam, silty loam, and silty clay loam soils in well-managed farms of
the region.
No-till farming is considered to improve topsoil physical properties, especially when combined with suitable
crop rotations and pastures (Álvarez et al., 2014). However, the prevalence of soybean mono-cropping in the
Pampean and Chaco regions promoted unfavourable topsoil physical conditions such as laminar and massive
aggregation, shallow compaction and decreased infiltration rates (Sasal, Andriulo and Taboada, 2006; Álvarez
and Steinbach, 2009; Álvarez et al., 2009, 2014). These structural forms were found to decrease soybean yields
under rainfed conditions (Bacigaluppo et al., 2011).
Status of the World’s Soil Resources | Main Report Regional Assessment of Soil Changes
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in Latin America and the Caribbean