Agriculture Reference
In-Depth Information
dairy region, with alfalfa (
Medicago sativa
) being an important forage crop. Crop
yields in Kalamazoo County, which surrounds the KBS LTER site, are similar to
national average yields (NASS 2013a, b). The soils of the area are Typic Hapludalfs
of moderate fertility, formed since the most recent glacial retreat ~18,000 years
ago, and the climate is humid continental (1027 mm yr
−1
average precipitation,
9.9°C mean annual temperature).
In 1988 we established a cropping-systems experiment along a management inten-
sity gradient that, by 1992, included four annual and three perennial cropping systems
plus four reference communities in different stages of ecological succession. The annual
cropping systems are corn-soybean-winter wheat rotations managed in four different
ways. One system is managed conventionally, on the basis of current cropping practices
in the region, including tillage and, since 2009, genetically engineered soybean and corn.
One is managed as a permanent No-till system, otherwise identical to the Conventional
system. A third is managed as a Reduced Input system, with about one-third of the
Conventional system's chemical inputs. In this system, winter cover crops provide
additional nitrogen, and mechanical cultivation was used to control weeds until a 2009
shift to herbicide-resistant crops that allowed the use of the herbicide glyphosate for
weed control in soybean and corn. A fourth system is managed biologically, with no
synthetic chemicals (or manure) but with cover crops and mechanical cultivation as
in the Reduced Input system. This system is U.S. Department of Agriculture-certified
organic. The three perennial crops are continuous alfalfa, short-rotation hybrid poplar
trees (
Populus
var.), and conifer stands planted in 1965.
The successional reference communities include (1) a set of Early Successional
sites abandoned from cultivation in 1989 and undisturbed except for annual burn-
ing to exclude trees, (2) a set of Mown Grassland sites cleared from forest in 1960
and mown annually but never tilled, (3) a set of Mid-successional sites released
from farming in the 1950s and 1960s that is now becoming forested, and (4) a set
of late successional Eastern Deciduous Forest stands never cleared for agriculture.
Complete descriptions of each system and community appear in Robertson and
Hamilton (2015, Chapter 1 in this volume).
Delivering Ecosystem Services
We identify five major ecosystem services that our annual cropping systems could
potentially provide: food and fuel, pest control, clean water, climate stabilization
through greenhouse gas mitigation, and soil fertility. These services are provided to
differing degrees in different systems and interact in sometimes unexpected ways.
In many respects, however, their delivery comes in bundles that can be highly
complementary.
Providing Food, Fuel, and Fiber
Without question, the most important ecosystem service of agriculture is the pro-
vision of food; fiber; and, more recently, fuel. To an ever-increasing extent, we
are dependent on high yields from simplified, intensively managed row-crop