Cover crop roots are an essential key to understanding ecosystem
services

Date:
August 13, 2020
Source:
Penn State
Summary:
To judge the overall effectiveness of cover crops and choose those
offering the most ecosystem services, agricultural scientists
must consider the plants' roots as well as above-ground biomass,
according to researchers who tested the characteristics of cover
crop roots in three monocultures and one mixture.



FULL STORY ==========================================================================
To judge the overall effectiveness of cover crops and choose those
offering the most ecosystem services, agricultural scientists must
consider the plants' roots as well as above-ground biomass, according
to Penn State researchers who tested the characteristics of cover crop
roots in three monocultures and one mixture.


========================================================================== "Almost everything that we know about the growth of cover crops is from measuring the above-ground parts and yet some of the benefits that we
want to get from cover crops come from the roots," said researcher Jason
Kaye, professor of soil biogeochemistry. "This study shows us that what
we see above ground is sometimes -- but not always -- reflective of the benefits below ground." Cover crops are widely used to increase the
quantity of organic carbon returned to the soil between cash crops such
as corn, wheat and soybean, as well as to limit erosion and to fix or
add nitrogen to the soil. Cover crop roots are known to play an essential
role in increasing soil organic carbon levels, Kaye noted, but the root
traits that impact carbon levels vary widely among cover crop species,
and this variation has yet to be characterized.

Recently, Kaye pointed out, cover crop mixtures have expanded in
popularity as a way to increase the diversity of cover crop benefits. His research group in the College of Agricultural Sciences has been conducting
a continuous experiment evaluating the effectiveness of various cover
crop mixtures since 2011.

In the latest study, conducted at Penn State's Russell E. Larsen
Agricultural Research Center at Rock Springs, recently published in
Renewable Agriculture and Food Systems, researchers evaluated cover crop treatments including monocultures of triticale, canola and crimson clover
as well as a five-species mixture dominated by those three species.

They tested the quantity, quality and spatial distribution of those
cover crop roots to learn about root-trait variation among species,
and how that variation impacts mixture design. They took root cores from
in-row and between-row locations to a depth of about 16 inches in both
fall and spring from cover crops planted after winter wheat.



========================================================================== Researchers also assessed cumulative carbon inputs for the entire rotation
to determine cover crop and cash crop root carbon contributions. They
measured the vertical and horizontal distribution of root biomass, the
ratio of root biomass to aboveground biomass -- known as the root-to-shoot ratio -- and related that to the amount of nitrogen in the plants to
determine how these parameters differed between cover crop treatments.

Cover crop mixtures increased total carbon inputs to soil because they simultaneously had high root and shoot inputs and they promoted higher
carbon inputs from corn crop residues, Kaye explained.

"The corn crop was more productive following the mixtures than following grasses, and while we harvest a lot of that productivity, some gets
left behind in residues," he said. "I think this is really interesting
because it shows that the effect of cover crops on soil carbon are not
just related to their own roots and shoots, but also how they affect
growth of the cash crops." The study revealed root trait differences
among the three important winter annual cover crops, canola, crimson
clover and triticale, lead researcher Joseph Amsili pointed out. The
research uncovered several important root traits, he added, including
the high root-to-shoot ratio and large production of between-row roots
for triticale, which is a hybrid of winter wheat and cereal rye.

"The five-species mix was associated with increased quantity and
distribution of roots compared to a crimson clover monoculture, which
shows the benefits of combining legumes that have limited root biomass
with brassica and grass species that produce greater root biomass,
but provide more nitrogen," said Amsili. Now an extension associate
in the Soil and Crop Sciences Section in the School of Integrative
Plant Sciences at Cornell University, he was a graduate student in the Department of Ecosystem Science and Management at Penn State when he spearheaded the research.

The study is important because the increased knowledge of cover crop
root traits it yielded improves the understanding of the linkages between
root traits and the services cover crops provide, Kaye explained. Going forward, he expects to find cover crops and design cover crop mixtures
that deliver unexpected ecosystem benefits and added boosts to cash
crops that follow.

"We'll now be able to think about what we want to occur in the soil
and then design mixtures that have the root traits that are best able
to provide those benefits," he said. "Advancing research on cover crop
root traits serves as a strong foundation for designing mixtures with complementary root traits. I envision that we will exploit lots of
different cover crop plants for different traits, both above and below
ground." This research was funded by the U.S. Department of Agriculture's National Institute of Food and Agriculture, Organic Research and Extension Initiative.


========================================================================== Story Source: Materials provided by Penn_State. Note: Content may be
edited for style and length.


========================================================================== Journal Reference:
1. Joseph P. Amsili, Jason P. Kaye. Root traits of cover crops
and carbon
inputs in an organic grain rotation. Renewable Agriculture and
Food Systems, 2020; 1 DOI: 10.1017/S1742170520000216 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200813155823.htm

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