Get to know your soil

Photos of the 2017-2018 Agronomy in the Field cohort for Central Iowa at the ISU Field Extension Education Lab. Photos by Hanna Bates.

An education in soil sampling

Last week I attended Agronomy in the Field, led by Angie Reick-Hinz, an ISU field agronomist.  The workshop focused on soil sampling out in a field. The cohort learned a lot of valuable insight into not only the science of soil sampling, but also practical knowledge from out-in-the-field experiences.

Taking soil samples in a field is critical in making decisions about fertilizer, manure, and limestone application rates. Both over and under application can reduce profits, so the best decision a farmer can make is based on a representative sample that accurately shows differences across his/her fields.

What do you need?

  • Sample bags
  • Field map
  • Soil probe
  • Bucket

When do you sample?

After harvest or before spring/fall fertilization times. Sampling should not occur immediately after lime, fertilizer, or manure application or when soil is excessively wet.

Where do you sample?

Samples taken from a field should represent a soil area that is under the same type of field cultivation and nutrient management. According to ISU Extension, the “choice of sample areas is determined by the soils present, past management and productivity, and goals desired for field management practices.”* See ISU Extension resources for maps and examples for where in the field to take samples.

Most importantly…

Like with everything that happens out in the field, it is important to keep records on soil testing so that you can evaluate change over time and the efficiency of fertilizer programs. As we say at the Iowa Water Center, the more data, the better! The more we learn about the soils, the better we can protect and enhance them. Healthy soils stay in place in a field and promote better crop growth by keeping nutrients where they belong during rain events. Not only can we monitor soil from the ground with farmers, but with The Daily Erosion Project. These combined resources, with others, can provide the best guidance in growing the best crop and protecting natural resources.

Interested in Agronomy in the Field? Contact Angie Rieck-Hinz at amrieck@iastate.edu or 515-231-2830 to be placed on a contact list.

* Sawyer, John, Mallarino, Antonio, and Randy Killorn. 2004. Take a Good Soil Sample to Help Make Good Decisions. Iowa State University Extension PM 287. Link: https://crops.extension.iastate.edu/files/article/PM287.pdf

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Hanna Bates is the Program Assistant at the Iowa Water Center. She has a MS in Sociology and Sustainable Agriculture from Iowa State University. She is also an alumna of the University of Iowa for her undergraduate degree. 
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Identifying Indicators for Soil Health

Breaking down our knowledge of soil enzymes

Post written by Marshall McDaniel, Assistant Professor in the Department of Agronomy at Iowa State University

As mentioned in a recent Washington Post article, there is a zoo beneath our feet in the soil. There are three properties of the soil, which are physical, chemical, and the biological properties. The emphasis on soil biology is, in large part, what separates soil health from the concepts of soil quality and the physical properties of soil (also known as soil tilth).  After all, only something that is living can be healthy (or unhealthy).  Many soil organisms are like us humans in that they require carbon as their main source of food in order to grow and reproduce.  Extracellular enzymes are proteins produced by microorganisms in soil to acquire carbon and nutrients from soil organic matter.

The McDaniel Lab was one of five to receive the Soil Health Literature and Information Review Grants from the Soil Health Institute. We will do a quantitative literature review on two of these enzymes – beta-glucosidase and polyphenol oxidase.  Beta-glucosidase can generally be thought of as being used for easily broken down, or labile, forms of soil carbon, and polyphenol oxidase for recalcitrant carbon.  In other words, think of labile carbon as a buffet of ‘yummy and healthy’ food that is nutritious and easy-to-digest for soil microbes, while recalcitrant carbon can be thought of as the equivalent of broccoli stems to human digestion.  We want to manage soils so that there is a large amount of the ‘yummy and healthy’ soil carbon for microbes to eat, and less of the ‘broccoli stems’.

Where the enzymes come in is that soil microbes will produce more of the beta-glucosidase enzyme if there is more ‘yummy and healthy’ forms of carbon in the soil, because it helps them to metabolize this form of carbon.  Conversely, if all you have left in the soil are ‘broccoli stems’, then as a soil microbe you are going to produce more polyphenol oxidase to metabolize this difficult to break down source of food.  Therefore, the ratio of these two enzymes holds promise as a good biological soil health indicator since it is an index of supply-and-demand for ‘yummy and healthy’ microbe food over ‘broccoli stems’.

What does this have to do with water?

Soil health and water quality go hand in hand. Improved soil health has the potential to increase water infiltration, increase water holding capacity, decrease surface runoff, decrease soil erosion, increase nutrient retention in the soil for plants, and more. By improving understanding of our soil biology, we can both better serve our natural resources and crop production.

Summer Update from the IWC Graduate Student Research Grant Program: Emily Martin

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Post submitted by Emily Martin, MS Environmental Science student at Iowa State University

Intensive farming and heavy nutrient application in the Midwest coupled with an extensive subsurface tile drainage network frequently leads to excessive nutrients in surface waters. As a result, heavy amounts of nitrogen and phosphorus has become a critical issue for policy and water research.

In spring 2017, I was awarded funding in the Iowa Water Center Graduate Student Supplemental Research Competition for my project titled, “Enhancing phosphate removal in woodchip bioreactors.” This project is conducted under advisement of Dr. Michelle Soupir at Iowa State University. A bioreactor is a subsurface trench along the edge of the field that can be filled with a range of different carbon sources. They are identified as a practice to help mitigate nutrient loss to flowing water systems, and so they deserve further research to understand their full capacity to capture water nutrients.

The goal of the project is to evaluate the ability of woodchip bioreactors to remove phosphorous by adding biochar as a phosphate (P) amendment to bioreactors. Objectives of the study are (1) to assess the effectiveness of different amendments on P removal in bioreactors and (2) to analyze the effect of influent P on overall removal.

We broke the project down into two main parts: a P sorption study and a column study. We completed part one during the month of June using 18 different types of biochar. The biochar was made by Bernardo Del Campo at ARTichar using three different temperatures of slow pyrolysis, 400°C, 600°C, and 800°C. We used six different types of biomass provided by the BioCentury Research Farm and the City of Ames, which are: switchgrass, corn stover, ash trees, red oak, mixed pine, and loblolly pine. The goal was to test a variety of biomass to see which would perform best as a P amendment and under which pyrolysis conditions they would function best.

Biochar is made using a process called pyrolysis. Pyrolysis is the burning of plant materials in a low to no oxygen chamber in order to “activate” the carbon structures that exists naturally within plants. The highly structured form of carbon rings in plants is desired for its stability and potential to adsorb or bind with chemicals, including phosphate and nitrate. There are two main types of pyrolysis: fast and slow, which refers to the amount of time the biomass remains in the pyrolysis chamber. Fast pyrolysis can be used to create biochar, but the yield is lower than slow pyrolysis. The temperature of pyrolysis can impact how the biochar interacts with different chemicals. In order to test these effects, we used three different temperatures when making our biochar.

Results from the P sorption study showed a few patterns. The main take away is that none of the biochars we tested adsorbed P exceptionally well; however, of the biochars we tested, the following were our top five P adsorbers:

  1. Corn stover @ 800°C
  2. Loblolly pine @ 600°C
  3. Red oak @ 600°C
  4. Switch grass @ 800°C
  5. Mixed pine @ 400°C

Because none of the biochars performed well in our P sorption test, we had to make a decision for the second part of the project. We came up with two options: (1) find new biomass and run the P sorption test again, or (2) test how well all 18 biochars remove nitrate from water. We chose option two and have begun nitrate batch tests, which will run throughout July. The batch tests are being run in one liter flasks and are tested at 4, 8, 12, and 24 hours to simulate woodchip bioreactor residence times found in the field.

After the nitrate batch test is complete, we will analyze results and decide if we will move forward with option one and see how other biomasses perform in a P sorption test.

Check back later on to learn more about the progress of this project!

 

A Day at the Lake

Post submitted by Hanna Bates, Program Assistant at the Iowa Water Center

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Slideshow of the Iowa Water Center Board visit to the Iowa Lakeside Laboratory.

This week, the Iowa Water Center Advisory Board held their bi-annual meeting at the Iowa Lakeside Laboratory at Lake Okoboji in northwestern Iowa. The IWC advisory board started in 2006, and is made up of representatives from around the state (list of members provided below). This was the first meeting for several of our board members, so we covered IWC history to start off the meeting and spent time discussing current and upcoming IWC activities.  Staff members and the advisory board also visited the research field sites for Elizabeth Swanner, Assistant Professor in the Department of Geological and Atmospheric Sciences at Iowa State University.

Swanner’s research is funded by the Iowa Water Center’s competitive annual seed grant program. This grant program funds one faculty member at an Iowa college as well as graduate students. Swanner’s project titled, “The role of iron mobility from anoxic sediments in stimulating harmful algal blooms,” received funding in 2016 and renewed funding for 2017. During the visit, Swanner described the project and demonstrated how samples are collected during a pontoon boat ride. Her research is focused on evaluating the potential that iron is released out of lake sediments, thus stimulating the blooming of toxic cyanobacteria in Iowa’s lakes during the summers. You can read more about her research here.

Follow her research on twitter at @betsyswanner.

The Iowa Water Center Board Members

  • Larry Weber (Chair), Director of IIHR—Hydroscience & Engineering, University of Iowa
  • Marty Adkins, Asst. State Conservationist at the Natural Resources Conservation Service
  • Daryl Smith, Professor Emeritus of Biology at University of Northern Iowa
  • Mary Skopec, Executive Director of Lakeside Laboratory
  • Jon Nania, Supervisory Hydrologist at the Iowa Water Science Center at the USGS (replacing Kevin Richards as USGS Iowa Water Science Center representative)
  • Jon Tack,  Water Quality Bureau Chief at the Iowa DNR (replacing Bill Ehm as IDNR representative)
  • Jake Hansen, Water Resources Bureau Chief at the Iowa Department of Agriculture and Land Stewardship (replacing Jim Gillespie as IDALS representative)
  • John Lawrence, Iowa State University Interim Vice President for Extension and Outreach
  • James Reecy, Professor in the Department of Animal Science at Iowa State University (replacing Wolfgang Kliemann as ISU Vice President for Research representative)

We’d like to extend a special thank you to Mary Skopec for making the arrangements for our meeting at Lakeside Lab. We highly recommend trekking to Okoboji for a tour of the campus or to take one of Lakeside’s academic courses. Lakeside does a variety of outreach, too – so bring the entire family!

Soil – Agriculture’s Reservoir

Post submitted by Hanna Bates, Program Assistant for the Iowa Water Center

The soil is like a sponge that holds water so it is available when crops need it. Wetter soil at the surface prevents deeper infiltration and so water is lost as surface runoff. Not only this, but soil moisture is also a variable that influences the timing and amount of precipitation in a given area. This is due to the impact it has on the water cycle. This cycle circulates moisture from the ground through evaporation and plant transpiration to the atmosphere and back to the ground again through precipitation. Therefore, the amount of water stored in the soil can affect the amount of precipitation received during the growing season.

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Satellite imaging from the European Space Agency. The center figure depicts imaging derived from SMOS.

According to Hornbuckle (2014), “we enter each growing season ‘blind’ as to whether or not there will be enough soil moisture and precipitation to support productive crops.” If there were a way to document and record water storage in the soil besides field measurements, we would have a better ability to predict future weather patterns and therefore, make better field decisions. Satellite remote sensing tools such as the European Space Agency’s Soil Moisture and Ocean Salinity (SMOS) and NASA’s Moisture Active Passive (SMAP) can be used to take such measurements. Before these tools can be used to estimate water storage and improve weather and climate predictions, researchers must compare them to what is actually measured within the soil. This process of confirming accuracy of a tool is called validation.

A project led by Dr. Brian Hornbuckle, and funded by the Iowa Water Center in 2014, sought to improve and validate SMOS and SMAP in near-surface soil moisture observations of Iowa. Hornbuckle used a network of soil moisture measurements located in the South Fork Watershed as a standard to validate the accuracy of SMOS and SMAP. At each site, soil moisture and precipitation was measured.

Some of the results of this research project are presented in a 2015 article published in the Journal of Hydrometeorology.  Rondinelli et al. found that SMOS and the network of soil moisture measurements detect different layers of the soil. SMOS takes measurements of the soil surface while the network observes a deeper level of soil. These results will allow scientists to better evaluate the accuracy of measurements from SMOS and SMAP and ultimately enhance our understanding of the water content of the soil surface.  As noted earlier, it is this layer of the soil that determines how much precipitation is lost to surface runoff.

In a subsequent study published in 2016, Hornbuckle et al. published further results that indicate new ways of using SMOS. Researchers found that SMOS can be used to look at water in vegetation, as opposed to water in the soil.  Hence SMOS might be used in the future to observe the growth and development of crops, and perhaps estimate yield and the time of harvest as opposed to conducting field surveys from the ground. It also has the potential to measure estimates of the biomass produced during the growing season, which could be useful to reach bioenergy production goals.

Research like this demonstrates that a single tool can be used in multiple ways to better understand our landscape. Not only this, but preliminary studies of SMOS also show that it is important to verify the accuracy of tools before relying on them. Like all research, the work is not done to identify all the potential uses for SMOS and SMAP.  A new NASA grant, in partnership with the Iowa Flood Center, will help get researchers even closer to making satellite measurements a useful, scientific tool to understand water near the soil surface.

References

Hornbuckle, Brian K. “New Satellites for Soil Moisture: Good for Iowans!.” A Letter from the Soil & Water Conservation Club President (2014): 20.

Hornbuckle, Brian K. Jason C. Patton, Andy VanLoocke, Andrew E. Suyker, Matthew C. Roby, Victoria A. Walker, Eswar R Iyer, Daryl E. Herzmann, and Erik A. Endacott. 2016. SMOS optical thickness changes in response to the growth and development of crops, crop management, and weather. Remote Sensing Environment (180) 320-333.

Rondinelli, Wesley J., Brian K. Hornbuckle, Jason C. Patton, Michael H. Cosh, Victoria A. Walker, Benjamin D. Carr, Sally D. Logsdon. 2015. Different Rates of Soil Drying after Rainfall Are Observed by the SMOS Satellite and the South Fork in situ Soil Moisture Network. Journal of Hydrometeorology. April 2015.

 

View from my Windshield: Observations of soil erosion across Iowa

Post written by Hanna Bates, Program Assistant at the Iowa Water Center

For the past couple of weeks, I have been on the road across Iowa. These trips vary in their purpose, but one thing that remains the same is the evident erosion in the fields along my travels. Regardless of where I am – whether it is in the Loess Hills visiting family or in the Des Moines Lobe for a meeting – spring rains have revealed that there are deep cuts in the bare brown soils where lush, even soils used to be.

Cruse et al. (2016) writes:

“Topsoil thinning is closely linked to loss of crop production potential. Typical statewide average erosion rates have only a minor impact on crop yields in the subsequent year. However, cumulative effects are far more significant and contribute to a loss of state revenue that becomes much more important as time progresses.”

The simple fact is that without soil there would be no life. In Iowa, we have high quality soils that, along with some good science and great farmers, enable us to be the top producers in corn, hog, and egg production. This leads to the question: What may be the ultimate cost of this productivity?

Cruse et al. (2016) conducted a study to determine the effects of erosion on commodity yields and to gauge the future impacts on the agricultural economy in Iowa. Researchers studied seven farm sites in Iowa with cropping history and available yield maps. The Daily Erosion Project was used to estimate crop yield impact on soil depth from 2007-2014. The average state loss across those years was 5.7 tons of soil per acre per year. “Assuming a 2.2 bushel per acre corn yield loss across 14 million acres in a given year and a corn price of $4.00/bu, the next year’s crop production loss would equate to approximately $4.3 million total across this land area” (Cruse et al. 2016). There are informational resources and federal programs available for soil conservation practices, but with a short-term economic market system, there is little motivation to participate.

Cruse et al. (2016) writes:

“Short-term minor yield impacts on a per acre basis create little incentive for investing in short-term soil conservation strategies available for many farmland renters. However, as the cumulative effect compounds the economic effect over time, landowners that have longer term planning horizons are much better positioned to recover their financial investments in soil conservation practices.”

To put is succinctly, a loss of soil leads to a loss of productivity, which leads to a financial loss for the state. The impacts of the above findings on decision-making out in the field may be significant given the short-term mindset of our commodity market. Making present-day investments to maintain soils may pay off in the end when compared to short-term commodity gains from year-to-year. Other research has revealed that there is hardly a piece of land in Iowa that is exempt from the problem of erosion. According to Cruse et. al. (2006), soil erosion affects everyone although it is spatially and temporally variable. With 55% of Iowa farmland leased rather than owner controlled (Duffy et al. 2013), an investment in soil saving practices will require candid conversations and real partnerships between a tenant and landowner.

Overall, the first step in making a change is being knowledgeable about your surroundings. Next time you are on the road, look out in the field and really see where you are travelling. Then, compare that to what the data shows on the Daily Erosion Project. You may be surprised about what you learn.

References

Cruse, R., D. Flanagan, J. Frankenberger, B. Gelder, D. Herzmann, D. James, W. Krajewski, Kraszewski, J. Laflen, J. Opsomer, and D. Todey. 2006. Daily estimates of rainfall, water runoff, and soil erosion in Iowa. Journal of Soil and Water Conservation. 61(4): 191-199.

Cruse, Richard M., Mack Shelley, C. Lee Burras, John Tyndall, and Melissa Miller. 2016. Economic impacts of soil erosion in Iowa. The Leopold Center for Sustainable Agriculture. Competitive Grant Report E2014-17.

Duffy, Michael, William Edwards, and Ann Johanns. 2013. Survey of Iowa Leasing Practices, 2012. Iowa State University Extension & Outreach. File C2-15.

Daily Erosion Project goes International

This week Dr. Richard Cruse, Professor in Agronomy at Iowa State University and Director of the Iowa Water Center, was invited to speak at the Rendez-vous végétal 2017 in Quebec, Canada. He provided a presentation on the cost of soil erosion and introduced the Daily Erosion Project to an international audience of soil and water professionals.

Below is an article published in le Bulletin des agriculteurs, a publication on new agricultural technologies in Quebec.  The article is written by Nicolas Mesy, an agronomist and freelance reporter and photographer. Topics the article explores include soil loss in Iowa, the science behind the Daily Erosion Project, and how soil erosion assessments can be a tool in decision-making.

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