Sustainable Soil Management Is More than What and How Crops Are Grown - Principles of Sustainable Soil Management in Agroecosystems - page 346

late 1940s and 1950s, and the development of herbicide technology made no-tillage
farming possible, and the practice began to spread in the United States in the 1960s,
and in Brazil, Argentina, Paraguay, and Australia in the 1970s. In 1973, Shirley
Phillips and Harry Young published the topic No-Tillage Farming , the first of its
kind in the world, and this was followed in 1984 by the topic No-Tillage Agriculture:
Principles and Practices by Phillips and Phillips (1984).
The modern successor of no-till farming—now generally known as conserva-
tion agriculture (CA)—goes much further as elaborated in Section 14.4. It involves
simultaneous application of three practical principles based on locally formulated
practices (Friedrich et al. 2009; Kassam et al. 2011a): minimizing soil disturbance
(no-till seeding); maintaining a continuous soil cover of organic mulch of crop resi-
dues and plants (main crops and cover crops including legumes); and cultivation of
diverse plant species that, in different farming systems, can include annual or peren-
nial crops, trees, shrubs, and pastures in associations, sequences, or rotations, all
contributing to enhance system resilience.
14.3.3 e xamPleS of l arge -S cale a gricultural S oil D egraDation
Examples of large-scale agricultural soil degradation from different parts of the
world appear to share several common experiences as can be seen from the cases
of South America, China, and Australia presented in the following sections. These
cases reflect contrasting agricultural environments ranging from the tropical and
subtropical environment with summer rainfall in Brazil, to subtropical environment
with winter precipitation in Western Australia, to temperate environment with win-
ter precipitation in northern China from east to west.
14.3.3.1 Brazil
Although in South America there is a diversity of soil types and ecologies, the domi-
nant croplands are found on Oxisols, Ultisols, and Alfisols situated for the most part
in tropical and subtropical climates. Usually, in undisturbed conditions, these soils
have good physical properties (deep, well-drained, stable aggregates, and rapid water
infiltration), but they have low natural soil fertility as reflected by low activity clay,
acidity, high aluminum content, high phosphorus fixation, and low base saturation.
These soils represent one of the world's biggest agricultural soil reserves. Therefore,
understanding the risk of soil degradation associated with mismanagement is cru-
cial. The dominant weather characteristics result in high intensity rainfall, especially
in the spring and summer seasons, which lead to high risk of water erosion and
nutrient leaching. Other processes associated with the weather characteristics are
the fast organic matter turnover due to higher soil temperature and moisture, which
favors microbial activity year-around. Further, there is also the potential to produce
high amounts of biomass due to the high solar radiation reaching the land surface. In
most humid ecologies, it is possible to design intensive cropping systems with at least
two crops per year accompanied with a diversity of cover crops to fill up the autumn
season window (Amado et al. 2006).
Until the 1960s, the agricultural features in South America were those of a
predominantly subsistent agriculture with land use change from native vegetation