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Oct 5, 2010, 4:37:20 PM10/5/10
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The pros and cons of Miscanthus --uses more water, leaches less
Published: Sep. 9, 2010

Source: Gregory F. McIsaac, 217-714-1835;gmci...@illinois.edu

URBANA — In the search for the perfect crop for biofuel production,
Miscanthus has become the darling to many. But in an effort to not be
charmed by its enormous potential for biomass production, researchers
at the University of Illinois are taking a careful look at the pros
and cons of its behavior in the field.

A recent study analyzed water quantity and quality in plots of
Miscanthus, switchgrass, corn, and soybeans and found that Miscanthus
used substantially more water, but reduced the potential for nitrogen
pollution to water bodies.

"We found that Miscanthus tends to dry out the soil much more than
corn, soybeans, or switchgrass later in the growing season," said Greg
McIsaac, environmental scientist in the College of Agricultural,
Consumer and Environmental Sciences. "This would likely reduce runoff,
stream flow and surface water supplies later in the summer and in
early fall, when streams are typically at their lowest. It could
reduce the amount of water available to those who are downstream in
late summer and early fall."

Switchgrass behaves like Miscanthus early in the growing season,
drying out the soil. It then goes into a reproductive mode and uses
very little water in the late summer and fall. McIsaac said that
Miscanthus's impact on water supply may be small if it is planted on
only a few acres in a watershed. "The severity of the impacts will
likely vary depending on the nature of the soils and climatic
conditions. In areas where water is in short supply, switchgrass may
be preferable, understanding that switchgrass creates much less
biomass than Miscanthus," he said.

"It will likely be in the farmer's economic interest to plant the most
productive crop, which may also use more water than their current
crops. When and where this occurs over significant areas, downstream
water users should consider how it is going to influence their water
supply. They may need to develop plans to address more frequent water
shortages, or perhaps attempt to influence the planting decisions
through incentives or policy. It is something to be aware of and plan
for if Miscanthus or a similar water-demanding crop becomes
economically attractive to farmers," he added.

The fact that both Miscanthus and switchgrass use more water early in
the growing season than corn and soybeans could be seen as a benefit
because flooding is often a problem that time of year. Drying out the
soil earlier in the spring would reduce runoff from spring rains, he
said, and thus reduce flood flows.

The study also looked at how nitrogen moves or "leaches" into the
ground water beneath the four crops. With corn and soybeans where the
field has tile drainage, the fertilizer and soil organic nitrogen gets
converted to nitrate which is highly soluble and moves with the water
to the tile drains. From there it moves out to the ditches and
streams, causing problems for drinking water supplies and contributing
to the hypoxia in the Gulf of Mexico.

The Miscanthus and switchgrass plots in the study received no added
fertilizer and grew vigorously without it.

Consequently, it wasn't surprising that the unfertilized Miscanthus
and switchgrass had much lower leaching than soybeans or fertilized

McIsaac explained that there are several factors at work, not just the
absence of applied fertilizers. "The roots in perennial grasses go
deeper into the soil. They're more extensive and they are active
earlier in the growing season — so if we had perennial corn, it might
behave more like these grasses. But even with soybeans, where we also
didn't apply fertilizer, the amount of leaching was almost as high as
with corn. So it's not just the absence of fertilizer, it's also the
perennial roots that retain more soil nitrogen."

"We did not apply fertilizer to Miscanthus or switchgrass because the
study was designed to look at a low-input biofuel," McIsaac said. "The
results showed that you can get high productivity without fertilizing
Miscanthus, at least for the first three to four years. It is likely
that if you apply fertilizer to Miscanthus and switchgrass, there
would be more leaching than what we saw in our study, with no
application. But because of the root activity, I would expect
fertilized Miscanthus and switchgrass to leach less than fertilized
corn. To be certain, this needs further study."

Miscanthus and Switchgrass Production in Central Illinois: Impacts on
Hydrology and Inorganic Nitrogen Leaching appears in the September-
October edition of the Journal of Environmental Quality. Authors in
addition to McIsaac are Mark B. David, and Corey A. Mitchell. Funding
for this research was provided by the C-FAR Strategic Research

News writer: Debra Levey Larson
phone: 217-244-2880; email: dla...@uiuc.edu

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