Cover crop and soil quality research presentations

Four research talks and one poster from the 2014 ASA-CSSA-SSSA annual meeting are available for viewing online. The research addresses the effect cover crops, manure application, and crop rotation on carbon, nitrogen, and water cycling and storage.

Building resilience: Effect of long-term crop rotation on soil water characteristics (Sarah Collier)

Long-term tillage, rotation, and perennialization effects on particulate and aggregate organic matter (Anna Cates)

Assessing benefits of radish as a cover crop (Megan Chawner)

Winter rye cover crop and forage comparison following corn silage in south central Wisconsin (Jaimie West)

Assessing greenhouse gas emissions of dairy manure from tannin in feeding trials (Claire Campbell, poster)

UW Field Day Tour Focuses on Greenhouse Gases and Crop Management

Tour examines viability of greenhouse gas reductions in Wisconsin agriculture.

MADISON, Wis. – The University of Wisconsin-Extension and UW-Madison invite farmers, agronomists, crop consultants, agri-business, governmental agencies, as well as the general public, to attend a special session on greenhouse gases and crop management at the Agronomy/Soils Field Day at 8 a.m. Aug. 27 at the Arlington Agricultural Research Station on Highway 51 about 5 miles south of Arlington. The field day includes greenhouse gas tours at 8:30 a.m. and 10:30 a.m. where you can see first hand how greenhouse gases are collected across different Wisconsin cropping systems, hear about recent research discoveries and learn about the applications of this research.

Agriculture contributes almost 10% of the greenhouse gas emissions in the US, with nitrous oxide and methane being the primary greenhouse gases from agriculture. Agricultural soil management contributes 75% of the nitrous oxide emissions in the US and 34% of the methane emissions in the US come from livestock and manure. Thus, the emphasis in agricultural research has been to identify management practices that can reduce nitrous oxide and methane losses. Reduction in greenhouse gas emissions are often considered an indicator of sustainability.

Several agriculture-led efforts are underway to reduce these emissions. For example, the Innovation Center for U.S. Dairy signed a memorandum of understanding with the U.S. Department of Agriculture (USDA) Secretary Tom Vilsack to reduce greenhouse gas emissions from dairy 25% by the year 2020. Additional efforts, such as the 25×25 Coalition, are spearheading efforts to increase renewable energy production in the United States and reduce greenhouse gas emissions.

“Our current research at UW is focused on understanding what the baseline losses are, how much they vary from year to year and how different cropping systems and management practices affect those losses,” said Matt Ruark, a UW-Extension specialist and assistant professor of soil fertility and nutrient management at UW-Madison. “We are also interested in assessing the emissions in relation to the production. Depending on the agricultural system being evaluated, the emissions may be calculated per gallon of milk, per bushel of grain or per energy produced.”

The University of Wisconsin is part of three large efforts in agricultural climate change mitigation and adaption:, and the Great Lakes Bioenergy Research Center. Both and (website under construction) are multi-disciplinary and multi-state projects funded by the USDA. The Great Lakes Bioenergy Research Center is funded through the U.S. Department of Energy. is led by the University of Wisconsin and in partnership with the Innovation Center for US Dairy and includes quantification of greenhouse gas emissions to improve models, assessment tools and user tools. These and other tools are currently being beta-tested and may be available and promoted soon for use to quantify effects of management across the supply chain.

“The quality of these tools and our understanding of how agriculture can help mitigate effects of climate change are grounded in the quality of the research conducted at the Arlington Ag Research Station,” Ruark said. “Another important aspect to this research is to assess all the co-benefits or trade-offs that come with a reduction in greenhouse gas emissions. We do not want to sacrifice profitability, water quality or soil quality in the process.”


UW-Extension, which receives the third largest amount of federal grants in the UW System, serves Wisconsin families, businesses and communities statewide through offices in all 72 Wisconsin counties and three tribal nations, continuing education services through all 26 UW System campuses, the statewide broadcasting networks of Wisconsin Public Radio and Wisconsin Public Television, and entrepreneurship and economic development activities by county throughout the state.

Contact: Matt Ruark,, 608-263-2889

Discovery Farms Field Days (8/11 and 8/28)

8112014DryRunFieldDayFlyerTwo field days are being hosted by the UW Discovery Farms program. The first is on August 11, 2014 in New Richmond, WI. Dr. Ruark will be presenting on nitrogen fertilizer efficiency, with a specific emphasis on nitrogen uptake in corn grain and corn silage. Additional presentations include an update on a Discovery Farms watershed project in Dry Run Watershed and residue and cover crop management to reduce runoff. Check out the flyer here. A dinner is included.


The second field day on August 28th is in Westby, WI, where Dr. Ruark will also be presenting on nitrogen use efficiency.

Notes from the Nitrogen Summit: The unseen nitrogen

The most common problem for farmers and crop consultants when determining an optimal nitrogen (N) rate for corn is that they never truly know if and by how much they “over” applied their N fertilizer. Under-application of N is readily seen in corn plants through classic N deficiency symptoms of yellowing of the midrib on lower leaves, likely resulting in reduced yields ( There are a few metrics used to determine if N was over-applied, such as the corn stalk nitrate test ( and end-of-season soil nitrate test. These tests require extensive sampling, only pertain to corn, and the relationship between stalk or soil nitrate values and crop yield are not well documented in Wisconsin. What I suggest here is the use of nitrogen use efficiency (NUE) calculations as simple metrics that can be used to understand how efficient you are (and can be) with N fertilizer.

The partial nutrient balance. One way that farmers and crop consultants can “see” the unused nitrogen is through nitrogen use efficiency calculations. There is no one specific calculation that is the true NUE, but instead the term NUE represents a suite of calculations that each have a specific meaning. The simplest calculation is the partial nutrient balance (PNB), which is the amount of N removed in the grain divided by the N applied ( A PNB of 1 (or slightly less) is considered ideal (i.e. system sustainability). If the value is much less than one, then this indicates there are opportunities for improvement. The PNB is a calculation that can be done by all growers on a field-by-field basis as long as they know their yield and the amount of N applied. Based on average N concentrations from corn samples analyzed at the University of Wisconsin Soil and Plant Analysis Laboratory, 0.70 lb-N is removed with 1 bu of corn grain (at 15.5% moisture). Therefore, multiplying 0.70 by the yield (bu/ac) gives an estimate of the amount of N removed. This calculation can also be used to “see” a simple N budget for the field (N input vs. N output) by subtracting the N removal from the N applied; if it is negative, more N was removed than what was applied. If it is positive, this is the amount of N remaining in the soil system. However, a lot of this N can still be tied up in the crop residue and for many systems there is a limit on how close we can get this value to 1. More accurate PNB values can be determined if the actual N concentration of the grain is known.

The value of the zero-N check strip. To get a sense of how much N is available from the soil, we can use the amount of N taken up by the corn plant (ears, stalks, and leaves – the entire above ground biomass) when no fertilizer is applied. This will involve cutting a whole plant at ground level, drying, and analyzing for total N; this is obviously not a standard sample practice. This value (total N uptake in unfertilized corn) can then be subtracted from the N in the above ground biomass from fertilized corn and then divided by the amount of N applied to give us the apparent crop recovery efficiency (RE). It is called the “apparent” crop recovery efficiency because we aren’t using the N taken up in root biomass and we are making assumptions about the fate of the applied N. In this case a value of 1 would indicate that the increase in N uptake from unfertilized to fertilized was the same as the amount of N applied (this is an unrealistic system). Snyder and Bruulsema (2007) provide some context, stating that values of 0.5 to 0.8 represent corn systems under best management practices. So, the value of the zero-N check strip allows you to know how much of your N was “needed” by the crop. This is in contrast to the partial nutrient balance calculation, which doesn’t indicate anything about crop need of the fertilizer, only the N balance of your soil and cropping system.

Recovery efficiency verifies the need of the fertilizer. Different soils will supply different amounts of N. For example, in an N rate trial conducted in 2011, corn fertilzied with 150 lb/ac of N at the Lancaster Agricultural Experiment Station had a RE of 63% while corn grown at the Arlington Agricultural Experiment Station had a RE of 28%. This indicates that would want to thing about altering our N rates at Arlington because less than 30% of the N that was applied was taken up. At Lancaster, we may not be able to improve much as nearly 70% of the N applied as take up by the plant.

Comparing the RE and the PNB. A stark contrast between these two calculations can be seen with irrigated sweet corn in the central sands in 2011. Yields without N were incredibly low, leading to RE of 88%, while the PNB was only 43% (150 lb/ac of N was used in this example). The 43% PNB is quite low, indicating a lot more N is applied to the system than is removed. However, a large percentage of the N applied ended up being taken up by the crop. Thus, for sweet corn on sandy soil, the PNB alone doesn’t tell the whole story regarding efficiency and fate of the N applied.

Overall, you’ll notice that I’ve used a lot of terms like “estimate” and “apparent” throughout the past few paragraphs. These calculations are not meant to be the last word on how efficient you are with your N fertilizer, but simply provide a tool for farmers and crop consultants to assess the current state of their N management. These measures need to be conducted across many growing seasons to get a range of efficiency values across different rainfall patterns. But, if we can make the “unseen” nitrogen “seen”, this will give both farmers and consultants more confidence with continuing their current N management plan or identify fields on which improvement strategies are warranted.

For more information on nitrogen use efficiency calculations see For more general information on nitrogen in soil check out Soil and Applied Nitrogen (

Cows Save the Planet – interview

Matt Ruark was recently on the radio on a show called Viewpoints, talking about the new USDA funded project to reduce GHG emissions from dairy, as well as to adapt dairy to changes in climate. Viewpoints is a radio magazine, which address real world issues. The current segment, titled “Cows save the planet” also includes an interview with Judith Schwartz, author of Cows Save the Planet.  

Take a listen to Cows Save the Planet: Reducing greenhouse gases on the farm (July 21)

One correction: US dairy contributes 0.2% of global greenhouse gas emissions, not 2%. US dairy contributes 2% of the US greenhouse gas emissions and 25% of the US agricultural emissions.


The future of Extension presentations?

…well maybe not just yet. But this video demonstrates how new technology can provide scientists with new ways for exploring and presenting data. The content of the video also touches on issue that are related to crop production and soil science. We live in world that has become wealthier and healthier in the past half decade. This is in part due to improved crop and soil management. However, with this increase in wealth and health comes an increase in food demand. As we move forward, the great challenge for agricultural and soil scientists’ is contained within that interactive graph. We must produce food sustainably in order to keep the world population from reverting back to the poor and unhealthy section of the graph.

Frontiers of Soil Science Workshop

A publication from the National Academies of Science was released from the 2005 Frontiers of Soil Science Workshop. This was an excellent workshop that covered all aspects of soil science research as well as the future and importance of soil science research. There were five graduate students invited to attend:
Amy Brock, University of Nevada, Las Vegas
Daniel Clune, Cornell University
Josh Heitman, Iowa State University
DeAnn Ricks Presley, Kansas State University
Matt Ruark, Purdue University
It was a great experience for all of us. And we have had a lot of success since then. Check out the great research these other scientists are conducting!

The passing of Norman Borlaug

Dr. Norman Borlaug passed away September 12, 2009 at the age of 95.  As a young scientist, I looked up to Dr. Borlaug, not only for the scientifc advancements he initiated, but also because of his ability take these advancements from test plots to entire continents, regarless of the polictical issue of the time.  I spent 6 years working in Borlaug Hall at the University of Minnesota and got to shake his hand once when he visited Purdue University.  As we reflect on the life and achievements of Dr. Borlaug, we must also think about this century’s challenges as it relates to food production and environmental sustatinability.

For more information and interesting articles about Dr. Borlaug, check out the following links:

San Francisco Chronicle

The Economist