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 That’s according to new University of Illinois research showing
cover crop adoption reached 7.2% in 2021, up from just 1.8% a
decade prior. The finding is the result of sophisticated
satellite-based remote sensing efforts that accurately detected
cover crops across 140 million acres of cropland and tracked
their expansion over 20 years.
“It's impossible to do field surveys for the whole Midwest. And
so, remote sensing can provide a cost-effective approach for
cover crop detection. We can monitor every field from the very
beginning to the end of the year, giving us a clear idea of what
happened over time,” says Qu Zhou, the study’s lead author and a
doctoral student in the Department of Natural Resources and
Environmental Sciences (NRES), part of the College of
Agricultural, Consumer and Environmental Sciences at Illinois.
Zhou is supervised by Kaiyu Guan, associate professor in NRES,
founding director of the Agroecosystem Sustainability Center,
and senior author on the study.
The uptick in cover crop adoption comes against a backdrop of
increasing state and federal incentive programs, a statistically
significant driver, according to the study.
“We analyzed the area of cover crops in each year with that
year’s funding and we found that it's highly correlated. We also
checked the investments across different states, showing some
states have higher cover crop percentages that are related to
their funding investment,” says Sheng Wang, research assistant
professor in NRES and study co-author.
To understand the impacts of conservation policies, the team
first had to assess the extent of cover crop adoption across the
region, a technical challenge. On-the-ground surveys are
accurate, but are time-consuming and difficult to scale up.
Previous remote-sensing-based estimates of cover crops lost
ground-based accuracy in favor of greater spatial coverage.
However, the majority of remote-sensing studies focused on
smaller areas, such as single states, and couldn’t be reliably
scaled nationwide.
In the new study, Guan’s team developed a novel algorithm to
detect cover crops from space, integrating a detailed
understanding of cover crop growth with machine learning and
creating high-resolution maps for the entire Midwest region.
To the untrained eye, satellite vegetation data looks like a
massive green blur across the landscape. Figuring out which
greens actually represented cover crops was a matter of timing.
The researchers developed algorithms to watch for bare soils
turning green between April and May, when most cover crops are
actively growing, then for soils to emerge again once cover
crops were terminated and before cash crop growth began.
Once they locked on that particular pulse of green, avoiding
patchy or asynchronous greening that would indicate weed growth
in fields, the researchers developed dynamic thresholds to
identify signals of cover crops, as their growth varies from
region to region and year to year.
“We compared our satellite data with census data for 2012-2017,
and validated it against field-based data from almost all the
available sources we could find, including our partners, the
USDA Risk Management Agency (RMA) and Indiana Department of
Agriculture. So we are confident we were detecting cover crops
with high fidelity in our model,” Guan says. “Every study has
uncertainties, but I think this is so far the most certain
answer.”
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“Leveraging remote sensing and novel algorithms gives
us confidence that the federal crop insurance program is being
administered effectively,” says James Hipple, RMA senior physical
scientist and a co-author of the study. “Additionally, it helps us
better understand the impact of USDA’s efforts to support farmers
who implement cover crops. In recent years, USDA has stepped up its
support for this important conservation practice, including adding
premium benefits for producers who plant cover crops, a new
partnership with Farmers for Soil Health, increases in technical and
financial assistance for cover crop adoption, and added
flexibilities for haying, grazing and chopping cover crops.”
The most significant gains in cover crop adoption occurred in recent
years and were strongly correlated with the onset of cover crop
assistance programs. For example, funding for cost-share programs
increased from $5 million in 2005 to $156 million in 2018, with the
greatest rate of investment after 2015. Cover crop adoption doubled
across the region between 2017 and 2021.
Although 7.2% adoption represents a four-fold increase since 2011,
it’s still a very small percentage.
“From a policy perspective, we are overly reliant on cost-share
assistance for this practice, but we do see innovation,” says
co-author Jonathan Coppess, associate professor in the Department of
Agricultural and Consumer Economics, also part of the College of
ACES at Illinois. “For example, Illinois and Iowa have led the way
using a discount in crop insurance premiums for adopting cover crops
and both have proven popular at a relatively low cost. USDA
experimented with it as well recently. Much more innovation in the
policy is needed if we are to help transition to widespread adoption
and successful management of this practice. The policies need to
incorporate risk components and do more than merely cover a portion
of the cost.”
Cover crops represent a potential risk in terms of the spring
planting window, in which farmers must quickly terminate cover crops
and get cash crop seeds planted amid increasingly challenging
weather conditions. But perhaps more notably, if not managed
properly, cover crops can be associated with yield penalties
affecting cash crops in the following season. A recent Stanford
University-led study, which relied on Guan’s satellite imagery and
analysis of cover crops in the Midwest, indicated cover crops can
decrease corn yield by around 5%.
“At the moment, cover cropping remains something for innovators and
early adopters; it hasn’t taken hold as a common practice,” Coppess
says. “A big part of the problem is that adding cover crops to the
rotation is a systems change for the farmer and the fields. It adds
cost, risk, and management challenges, but important learning is
happening among innovators and farmers are gaining valuable
experience.”
The article, “Recent rapid increase of cover crop adoption across
the U.S. Midwest detected by fusing multi-source satellite data,” is
published in Geophysical Research Letters [DOI:
10.1029/2022GL100249]. This work was primarily supported by the USDA
Risk Management Agency (RMA), USDA National Institute of Food and
Agriculture (NIFA) Foundational Program awards, U.S. Department of
Energy's Advanced Research Projects Agency-Energy (ARPA-E) SMARTFARM
projects, and an NSF CAREER Award.
[Sources: Kaiyu Guan, Qu Zhou, Sheng
Wang, Jonathan Coppess, and Jim Hipple
News writer: Lauren Quinn] |
