Sustainable Soil Management Is More than What and How Crops Are Grown - Principles of Sustainable Soil Management in Agroecosystems - page 352

degraded soil structure as indicated by soil surface sealing, low mesoporosity (pores
of diameter <60 µm), unstable soil aggregates, and low SOM content, all of which
reduce water infiltration and soil water retention (Elliott 1986; Fabrizzi et al. 2005),
creating a harsh environment for crop growth. Notably, after a long period with con-
ventional tillage, a hard plow pan forms, which prevents water infiltration and results
in a lower soil water storage capacity, increased runoff, and erosion. Dust storms
have increased considerably in recent years (Zhang et al. 2004; Wang et al. 2006).
CA using no-till can improve soil water storage once the hard plow pan is broken
through subsoiling or ripping. Soil residues cover and no or minimum tillage can
reduce evaporation and promote soil water infiltration by mitigating the direct attack
of rainfall and decreasing soil crusting. The decomposed roots can form the chan-
nels in the soils, thereby reducing runoff and increasing soil water infiltration. A
positive effect of CA in conserving soil water has been proved in demonstration sites
established in dryland areas of China (Wang et al. 2008; He et al. 2008, 2009a,b,
2011).
14.4 NURTURING SOILS AND LANDSCAPES
AS LIVING BIOLOGICAL SYSTEMS
Alongside the concern for soil erosion and the destruction of soil structure and soil
life caused by frequent and intensive tillage has been the growing understanding of
the important role soil life and soil biology play in the maintenance of soil health. In
the 1940s, Eve Balfour referred to this in terms of “the living soil” as being a neces-
sary condition for healthy crops, environment, and people (Balfour 1943; Primavesi
1984). According to Doran and Zeiss (2000):
Soil health is the capacity of soil to function as a living system with ecosystem and land
use boundaries, to sustain plant and animal productivity, maintain or enhance water
and air quality, and promote plant and animal health.
According to Peter Trutmann, quoted in FAO (2008), this emphasizes a unique
property of biological systems, since inert components cannot be sick or healthy.
Management of soil health thus becomes synonymous with management of the liv-
ing portion of the soil to maintain essential functions of soil to sustain plant and
animal productivity, maintain or enhance water and air quality, and promote plant
and animal health. According to David Wolfe, quoted in FAO (2008), healthy soils
maintain a diverse community of soil organisms that help to control plant disease,
insect, and weed pests; form beneficial symbiotic associations with plant roots (e.g.,
nitrogen-fixing bacteria and mycorrhizal fungi); recycle essential plant nutrients;
improve soil structure (e.g., aggregate stability) with positive repercussions or soil
water and nutrient holding capacity; and ultimately improve crop production.
In this context, ongoing supply of carbon-rich organic matter for soil organisms is
essential, from which they source both energy and nutrients. Examples of manage-
ment practices for maximizing soil health include maintaining vegetative cover of the
land year-round to increase organic matter input and minimize soil erosion, more reli-
ance on biological as opposed to chemical approaches to maintain crop productivity