New Jackson lab manuscript on plant-associated soil microbes

The Randy Jackson lab has released a new manuscript titled “Bioenergy cropping systems that incorporate native grasses stimulate growth of plant-associated soil microbes in the absence of nitrogen fertilization”.


The choice of crops and their management can strongly influence soil microbial communities and their processes. We used lipid biomarker profiling to characterize how soil microbial composition of five potential bioenergy cropping systems diverged from a common baseline five years after they were established. The cropping systems we studied included an annual system (continuous no-till corn) and four perennial crops (switchgrass, miscanthus, hybrid poplar, and restored prairie). Partial- and no-stover removal were compared for the corn system, while N-additions were compared to unfertilized plots for the perennial cropping systems. Arbuscular mycorrhizal fungi (AMF) and Gram-negative biomass was higher in unfertilized perennial grass systems, especially in switchgrass and prairie. Gram-positive bacterial biomass decreased in all systems relative to baseline values in surface soils (0–10 cm), but not subsurface soils (10–25 cm). Overall microbial composition was similar between the two soil depths. Our findings demonstrate the capacity of unfertilized perennial cropping systems to recreate microbial composition found in undisturbed soil environments and indicate how strongly agroecosystem management decisions such as N addition and plant community composition can influence soil microbial assemblages.

You can read the manuscript here (PDF).

More Sustainable Feedstock for Ethanol

Picture: Researcher Gregg Sanford stands before a plot of giant miscanthus at Arlington.


Perennial crop yields can compete with corn stover, study suggests
By Mark E. Griffin

A six-year Great Lakes Bioenergy Research Center (GLBRC) study on the viability of different bioenergy feedstocks recently demonstrated that perennial cropping systems such as switchgrass, giant miscanthus, poplar, native grasses and prairie can yield as much biomass as corn stover.

The study is significant for addressing one of the biofuel industry’s biggest questions: Can environmentally beneficial crops produce enough biomass to make their conversion to ethanol efficient and economical?

Since 2008, research scientists Gregg Sanford and Gary Oates, based in the lab of CALS agronomy professor Randy Jackson, have worked with colleagues at Michigan State University (MSU) to cultivate more than 80 acres of crops with the potential to become feedstocks for so-called “second-generation” biofuels, that is, biofuels derived from non-food crops or the nonfood portion of plants. They’ve grown these crops at the CALS-based Arlington Agricultural Research Station and at MSU’s Kellogg Biological Station.

“We understand annual systems really well, but little research has been done on the yield of perennial cropping systems as they get established and begin to produce, or after farmland has been converted to a perennial system,” says Oates.

To find out basic information about how well certain crops produce biomass, Sanford and Oates tested the crops across two criteria: diversity of species, and whether a crop grows perennially (continuously, year after year) or annually (needing to be replanted each year).

Highly productive corn stover has thus far been the main feedstock for second-generation biofuels. And yet perennial cropping systems, which are better equipped to build soil quality, reduce runoff, and minimize greenhouse gas release into the atmosphere, confer more environmental benefits.

Corn, when grain is included, proved to be most productive over the first six-year period of the study at the Wisconsin site, but giant miscanthus, switchgrass, poplar and native grasses were not far behind. At the MSU site, where soil is less fertile, miscanthus actually produced the same amount of biomass as corn (grain included) in the experiment, with poplar and switchgrass within range.

“All of this means that, at large scales and on various soils, these crops are competitive with corn, the current dominant feedstock for ethanol,” Sanford says.

Now in the midst of the study’s eighth year, Sanford says the study will continue for the foreseeable future.

“We know that perennial systems can prevent negative impacts such as soil erosion and nitrate leaching, and that they also provide habitat for native species that provide beneficial ecosystem services,” Sanford says. “But there are still a lot of questions we want to answer about soil processes and properties— questions that take many years to answer.”

Study Suggests Perennial Crop Yields Can Compete with Corn Stover

A six-year Great Lakes Bioenergy Research Center (GLBRC) study on the viability of different bioenergy feedstocks recently demonstrated that perennial cropping systems such as switchgrass, giant miscanthus, poplar, native grasses, and prairie can yield as much biomass as corn stover.

The study is significant for beginning to address one of the biofuel industry’s biggest questions: can environmentally beneficial crops produce enough biomass to make their conversion to ethanol efficient and economical?

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MIRG and Pasture Productivity

Do pastures under management-intensive rotational grazing (MIRG) differ from grasslands under other management in terms of forage quality and quantity, carbon sequestration and biological soil activity? Researchers at the University of Wisconsin-Madison set out to answer these questions and discover some of the reasons behind differences in pasture productivity. They compared MIRG to continuous grazing, mechanically harvested forages, and unmanaged grassland similar to land enrolled in the Conservation Reserve Program (CRP). Their findings indicate that MIRG may provide a higher quality and quantity of forage, and more potential for carbon sequestration, compared to the other management systems.

Full document here: CIAS Research Brief 95

“Second generation” Feedstocks Reduce Greehouse Gas Emissions

Left photo by James Tesmer, Right photo by Gregg Sanford.

Left photo by Andrew Dean, Right photo by Gregg Sanford.

Scientists at the University of Wisconsin–Madison and Michigan State University (MSU) report today that emissions of the potent greenhouse gas nitrous oxide (N2O) can be reduced significantly by replacing annual biofuels feedstocks, such as corn, with second-generation, perennial feedstocks such as switchgrass.

“If we are going to add second-generation biofuel crops to the landscape, we need a better sense of how they’ll impact ecosystem processes such as greenhouse gas emissions,” says Gary Oates, research scientist in the Great Lakes Bioenergy Research Center (GLBRC) Sustainability group and the paper’s lead author.

The study, published in the journal Global Change Biology–Bioenergy, compares eight different biofuel cropping systems planted at both UW–Madison’s Arlington Agricultural Research Station and MSU’s Kellogg Biological Research Station.

So-called “first-generation” biofuel crops in the study include corn, soybean, and canola, which need to be replanted each year. Second-generation crops include switchgrass, miscanthus, poplar, a mixture of native grasses, and a prairie mix. These perennial crops require an “establishment phase” after planting, a few years during which they settle into a “production phase.”

“We understand annual systems like corn really well but, up till now, little research has been done on perennial N2O emissions during that establishment phase, when farmland has just been converted to a perennial system,” says Oates.

Emissions data collected during the first three years of the long-term experiment indicate that cumulative N2O emissions from fertilized second-generation cropping systems were 57% lower than emissions from first-generation systems. In addition, cumulative N2O emissions from unfertilized second-generation cropping systems were 85% lower compared to first-generation systems.

If second-generation biofuel crops can meet productivity needs with fewer fertilizer inputs, the study suggests, they have the potential to dramatically reduce N2O emissions compared to the first–generation crops used for almost all of today’s biofuel production.

But the researchers also conclude that the relationship between N2O flux and environmental conditions is not generalizable across numerous and varied cropping systems, indicating that the computer models currently used to predict N2O emissions, especially for perennials, need improvement.

“We’ve definitely gained a better understanding of biofuel cropping systems, but the underlying mechanisms driving N2O production remain elusive,” says Randy Jackson, co-leader of GLBRC’s Sustainability research group. “The amounts of water, nitrogen, and carbon in the soil are clearly important but we have more work to do.”

The first phase of the analysis used data collected between 2009 and 2011. Researchers are now in the process of analyzing an additional three years of data collected during the production phase of the perennial systems. A primary focus of the current work is gaining a better understanding of the genetic make-up of the soil’s microbial community and how knowledge of that genetic make-up might be used to predict N2O emissions for biofuel cropping systems.