Agriculture Reference
In-Depth Information
The Organic system produced 1370 kg ha
−1
yr
−1
less grain than the Integrated
Conventional system, but resulted in substantial gains in soil C (820 kg ha
−1
yr
−1
)
and reduced nitrate leaching losses by 42 kg N ha
−1
yr
−1
(Table 15.3). Increasing
crop diversity in the LFL Organic system did not further improve these biogeo-
chemical benefits (Snapp et al. 2010b).
In the MCSE, the gains in soil C with Biologically Based (Organic) manage-
ment were higher than those obtained under No-till management (Table 15.3), but
less than those associated with set asides or planting a perennial crop (Grandy and
Robertson 2007, Piñeiro et al. 2009). The 50% reduction of nitrate leaching in the
Organic system at the LFL was a significant achievement.
Designing Sustainable Agricultural Systems
KBS research highlights some of the trade-offs involved in developing row-crop
systems that are more sustainable—more profitable, more environmentally benign,
and more socially acceptable: in short, those that deliver a more desirable mix
of ecosystem services (Robertson and Harwood 2013, Syswerda and Robertson
2014). Evidence from KBS and elsewhere (Robertson et al. 2007; Snapp et al.
2010a, b) shows that all services cannot be maximized simultaneously in agricul-
tural systems; consequently, it is necessary to set priorities. Presently, priorities
are set largely by markets and government policies that incentivize production and
allow environmental costs to be externalized to society as a whole. Understanding
trade-offs, especially with respect to yields, is an essential first step for incentiv-
izing additional services. To the extent that most farmers' first priority is staying in
business (Swinton et al. 2015b, Chapter 13 in this volume), the cost of providing
any service that reduces farm profitability must be borne by society. This is par-
ticularly true for those services perceived primarily as a public good—greenhouse
gas mitigation and water quality, for example. For services perceived to have local
value—soil C storage as it affects soil fertility and crop diversity as it affects pest
suppression, for example—costs are more willingly borne by the farmers (Swinton
et al. 2015b, Chapter 13 in this volume). For example, biologically based row-crop
management is shown at KBS LTER to improve soil C storage and water quality,
but at the expense of reduced yields in cereals. Making up the yield difference rep-
resents the cost of providing these services.
The relationships between yield and other ecosystem services are complex.
Management practices are commonly bundled within systems, so it can be dif-
ficult to prescribe one practice alone. In the MCSE No-till system, for example,
the benefits of low soil disturbance come with a need for greater herbicide use.
Within the Reduced Input and Biologically Based systems, the duration of living
plant cover is high, providing water quality and soil C benefits, but soil disturbance
is also high. These systems also have enhanced rotational diversity that promotes
biological N fixation, reducing the requirement for N fertilizer inputs, but more
fossil fuel is required to plow under the cover crop, kill weeds, and enhance residue
contact with soil to promote the mineralization and release of nutrients in concert
with crop demand.
