Agriculture Reference
In-Depth Information
Table 9.1. Description of the KBS LTER Main Cropping System Experiment (MCSE).
a
Cropping
System/Community
Dominant Growth Form
Management
Annual Cropping Systems
Conventional (T1)
Herbaceous annual
Prevailing norm for tilled corn-soybean-winter
wheat (c-s-w) rotation; standard chemical inputs,
chisel-plowed, no cover crops, no manure or compost
No-till (T2)
Herbaceous annual
Prevailing norm for no-till c-s-w rotation;
standard chemical inputs, permanent no-till, no
cover crops, no manure or compost
Reduced Input (T3)
Herbaceous annual
Biologically based c-s-w rotation managed to
reduce synthetic chemical inputs; chisel-plowed,
winter cover crop of red clover or annual rye, no
manure or compost
Biologically Based (T4)
Herbaceous annual
Biologically based c-s-w rotation managed
without synthetic chemical inputs; chisel-plowed,
mechanical weed control, winter cover crop of
red clover or annual rye, no manure or compost;
certified organic
Perennial Cropping Systems
Alfalfa (T6)
Herbaceous perennial
5- to 6-year rotation with winter wheat as a
1-year break crop
Poplar (T5)
Woody perennial
Hybrid poplar trees on a ca. 10-year harvest
cycle, either replanted or coppiced after harvest
Coniferous Forest (CF)
Woody perennial
Planted conifers periodically thinned
Successional and Reference Communities
Early Successional (T7)
Herbaceous perennial
Historically tilled cropland abandoned in 1988;
unmanaged but for annual spring burn to control
woody species
Mown Grassland (never
tilled) (T8)
Herbaceous perennial
Cleared woodlot (late 1950s) never tilled,
unmanaged but for annual fall mowing to control
woody species
Mid-successional (SF)
Herbaceous annual +
woody perennial
Historically tilled cropland abandoned ca. 1955;
unmanaged, with regrowth in transition to forest
Deciduous Forest (DF)
Woody perennial
Late successional native forest never cleared
(two sites) or logged once ca. 1900 (one site);
unmanaged
a
Site codes that have been used throughout the project's history are given in parentheses. Systems T1-T7 are
replicated within the LTER main site; others are replicated in the surrounding landscape. For further details, see
Robertson and Hamilton (2015, Chapter 1 in this volume).
~41 kg N ha
−1
to the atmosphere. These N removals represent the minimum amount
of N that must be replaced annually to avoid N depletion—the minimum because not
included are additional N losses by other pathways such as leaching and denitrification
(Fig. 9.1). Although a small amount of N is added as deposition (see Nitrogen
Deposition below), most N is replaced by either biological or industrial fixation of
atmospheric N
2
or by application of organic N fertilizers such as compost or manure.
