Agriculture Reference
In-Depth Information
Conservation Agriculture
Conservation agriculture is a broad term that considers many of the system design
principles evaluated here (Govaerts et al. 2009). This management approach shifts
the emphasis from conservation tillage practices to principles-based management
that emphasizes: (1) reduction in tillage to ensure disturbance remains below a set
percentage, (2) sufficient retention of residues to provide cover and protect soil
from erosive forces, and (3) diversified crop rotations that mitigate against pest
problems and ensure a mixture of residue qualities and heterogeneous root system
inputs belowground.
The success of permanent no-till management at the MCSE is illustrated by the
No-till system's high grain yields (~8% more than Conventional management) and
soil C gains (Table 15.3). It is notable that no-till was implemented with no increase
in fertilizer N inputs and only a modest increase in herbicide inputs compared to
conventional management. Energy inputs are substantially lower with reduced reli-
ance on tillage (e.g., 4.9 GJ ha
−1
yr
−1
in the MCSE No-till system compared to
7.1 GJ ha
−1
yr
−1
in the Conventional system, Table 15.2), despite modest increases
in herbicide use in No-till. Declining fossil fuel supplies and high energy costs
are important arguments for the adoption of conservation tillage equipment and
practices.
Published studies that have evaluated crop diversification and conservation till-
age have shown that only the combination of rotational diversity and reduced till-
age is an effective means to enhance soil C and N over the long term (West and
Post 2002, Govaerts et al. 2009). Overall, the MCSE showed that permanent no-till
management of a corn-soybean-wheat rotation was an effective means to modestly
improve a broad range of ecosystem services. It is important to note that this was
the only alternative practice that enhanced grain yield relative to conventional man-
agement, which may in large part explain the broad adoption of conservation tillage
practices. The reduction in number of field operations, leading to reduced fuel and
time requirements, may also play a significant role in farmer adoption. However,
adoption has not been universal nor, where it has been adopted, is it usually perma-
nent (Horowitz et al. 2010). This is particularly so among farmers who produce on
heavy (clayey) soils, or without ready access to herbicides. Another constraint to
continued and future adoption of no-till is the increasing number of weed species
that are evolving resistance to the primary herbicides used in no-till cropping sys-
tems (i.e., glyphosate), which threaten to reduce the longer-term viability of no-till
production practices (Johnson et al. 2009) or increase the use of older herbicide
chemistries that have greater potential for nontarget impacts and ecosystem dis-
services (Mortensen et al. 2012).
A first step in promoting conservation agriculture might include improved knowl-
edge about farmer adoption of management practices such as tillage and extended
cover. Policies that support innovative conservation practices might include instru-
ments that mitigate risk associated with adoption and adaptive research—these
could go far toward enhancing the adoption of conservation agriculture (Feinerman
et al. 1992). Innovative research will be required to support adoption by organic
farmers and smallholder farmers in developing countries, groups that have thus
