Agriculture Reference
In-Depth Information
range in size from 1 to 7.5 ha, adjoin a number of different habitat types, and
have a variety of perimeter complexities. Regular sampling activities include
agronomic yields.
Biodiversity Gradient Experiment
The Biodiversity Gradient Experiment was established on the LTER main site
(Fig. 1.2) in 2000 to investigate the effect of plant species diversity across a gradi-
ent ranging from bare ground to 1, 2, 3, 4, 6, and 10 species. Small plots (9 × 30
m) are within four randomized complete blocks and are managed much like the
MCSE Biologically Based system (i.e., no synthetic chemical inputs). This experi-
ment reveals how crop species and rotational complexity affect yield, weed com-
petition, soil biogeochemical processes, microbial diversity, and other variables
(Gross et al. 2015, Chapter 7 in this volume).
Resource Gradient Experiment
The Resource Gradient Experiment was established on the LTER main site
(Fig. 1.2) in 2003 to investigate nitrogen and water constraints on crop yield.
MCSE annual crops (either corn, soybean, or wheat) are nitrogen-fertilized at
nine different rates and are either irrigated or rain-fed. Fertilizer rates differ by
crop; for corn the range has been 0 to 292 kg N ha
−1
and for wheat 0 to 180 kg
N ha
−1
. Soybeans are normally not fertilized (but were in 2012). Irrigation is
sufficient to meet plant water needs as predicted by weather and SALUS, a crop
growth model that calculates instantaneous water balance (Basso and Ritchie
2015, Chapter 10 in this volume). A linear move irrigation system applies water
0-3 times per week during the growing season depending on recent rainfall
and crop water need. Crops are otherwise managed as for the MCSE No-till
system. In addition to crop yield, greenhouse gas exchanges between soils and
the atmosphere are measured in various treatments (Millar and Robertson 2015,
Chapter 9 in this volume).
Living Field Lab Experiment
The Living Field Laboratory (LFL) was established on land just north of the
MCSE in 1993 to investigate the benefits of leguminous cover crops and compos-
ted dairy manure in two integrated systems compared to a conventional and an
organic agricultural system. “Integrated” refers to targeted, banded applications
of herbicide, reduced tillage, and stringent accounting of nitrogen inputs using
the pre-side-dress nitrate test (PSNT) or nitrogen analysis of composted dairy
manure. During the past 15 years, a crop rotation of corn-corn-soybean-wheat
has been compared to continuous corn where every entry point of the rotation
was present each year. A number of soil and crop variables were measured at the
LFL from 1993 to 2003 (Snapp et al. 2010); since 2006 the LFL has initiated new
studies including a perennial wheat project (Snapp et al. 2015, Chapter 15 in this
volume). The LFL was decommissioned in Fall 2014.
