Sustainable Soil Management Is More than What and How Crops Are Grown - Principles of Sustainable Soil Management in Agroecosystems - page 359

and management intensive and relatively complex to learn and implement. They
are dynamic systems, offering farmers many possible combinations of practices
to choose from and adapt, according to their local production conditions and con-
straints (Kassam et al. 2009; Godfray et al. 2010; FAO 2011b; Pretty et al. 2011).
The development of SCPI requires building on the core principles and practices
outlined above as the production base and finding ways to support and self-empower
producers to implement them all, through participatory approaches and stakeholder
engagement. In addition, SCPI must be supported by coherent policies, institutional
support, and innovative approaches to overcome any barriers to adoption. Monitoring
and evaluating the progress of change in production system practices and their out-
comes at the farm and landscape levels are critical.
One of the main criteria for ecologically sustainable production systems such as
CA is the maintenance of an environment in the root zone to optimize conditions for
soil biota, including healthy root function to the maximum possible depth. Roots are
thus able to function effectively and without restrictions to capture plant nutrients
and water as well as interact with a range of soil microorganisms beneficial for soil
health and crop performance (Uphoff et al. 2006; Pretty 2008). In such systems with
the above attributes, there are many similarities to resilient “forest floor” conditions
(Kassam et al. 2009). Maintenance or improvement of SOM content and soil struc-
ture and associated porosity are critical indicators for sustainable production and
other ecosystem services.
A key factor for maintaining soil structure and organic matter is to limit mechani-
cal soil disturbance in the process of crop management. For this reason, no-tillage
production methods—as practiced, for example, in CA—have in many parts of the
world been shown to improve soil conditions, reduce degradation, and enhance pro-
ductivity. However, as a stand-alone practice, the elimination of tillage would not
necessarily lead to a functioning sustainable production system. This requires a set
of complementary practices to enable a functioning soil system as well as the whole
agroecosystem to deliver a range of ecosystem services.
The contribution of practices that implement the technical principles of CA—
including mulch cover, no-tillage, legume crops, and crop rotations—in important
ecosystem services is shown in Table 14.1 and Figure 14.1a and b. Even where it is not
possible to install all desirable practical aspects in the production system at the same
time, progressive improvements toward those goals should be encouraged. However,
for any agricultural system to be sustainable in the long term, the rate of soil erosion
and degradation (loss of organic matter) must never exceed the rate of soil formation
(though the steeper the slope, the greater the danger that this could happen). In the
majority of agroecosystems, this is not possible if the soil is mechanically disturbed
(Montgomery 2007). For this reason, the avoidance of mechanical soil disturbance
can be seen as a starting point for sustainable production. Once it has been brought
into good physical condition, no further tilling of the soil is therefore a necessary
condition for sustainability but not a sufficient condition. For SCPI, including eco-
system services, other complementary techniques are required as mentioned already,
of which the practices related to the above three CA principles constitute the bare
minimum for ecological sustainability (FAO 2011b).