Objectives

  • One of the objectives of this study is to determine if residue removal has a negative impact on soil properties.
  • We were also looking to establish a preliminary threshold of residue removal that could help reduce wind erosion in western Kansas.
  • A personal objective of mine for this project was to gain broader understanding about the biofuels industry.
  • Introduction

    With recent growth in world population, the demand for natural resources is ever increasing. At the same time, the build up of greenhouse gasses in our atmosphere has jump-started a search for renewable energy sources. One of these is biofuels. Biofuels are defined as any fuel that is made directly from organic matter. Corn stover has become a common feedstock for biofuels because it has a high cellulose content and perceived ubiquity in the United States.

    While residue has potential for biofuel production, the process could potentially harm the soil. In this study we have tested soil properties to better understand how different rates of removal affect those soil properties that govern wind erodibility.

    The model shown above displays how wind erosion works with different size soil particles. The large particles 'creep' across the soil surface. The medium size particles are carried short distances. This is called saltation. The small particles are picked up by the wind and are 'suspended' in the air. Suspension is a large problem in many parts of the world, especially in Kansas.

    The figures above are representative of The Dust Bowl that plagued the west in the 1930's. The photo on the left was taken on April 14, 1935. As shown, large dust storms formed clouds of dust that were inescapable. The Dust Bowl is a horrific example of what can happen if wind erosion is not managed in a sustainable way. The diagram to the right shows the areas that were most effected by The Dust Bowl. As you can see, western Kansas is among a large area that was plagued with dust storms between the years of 1935 and 1940.

    Materials and Methods

    This research was conducted at the Kansas State University-Northwest Research Extension Center in Colby, KS. Residue was removed from the plot in April of 2014. Studies like this always require repetition. Therefore, we removed the residue at each rate in three different plots. This gave us three treatments of 0, 25, 50, 75, and 100% removal. Each treatment represents a different removal rate that a producer might consider using when harvesting corn stover for fuel production.

    On June 2nd, 2014, we took a trip to Colby. We spend the day collecting data and soil samples. We took a lot of samples to test back in the lab. In the next few weeks I spent a lot of time testing the soil for different properties including, but not limited to:

  • Bulk Density
  • Water Content
  • Dry Aggregate Stability
  • Aggregate Size Distribution
  • Soil N,C, and P Content
  • Texture
  • Surface Roughness
  • I really enjoyed some of the tests because I had never done them before. For instance, Aggregate Size Distribution is found using the rotary sieve shown below. Soil is placed in a shoot on the right side of the machine. The shoot shakes the soil into the first sieve which only allows particles smaller than .42mm to pass through. The machine is called a rotary sieve because it slowly spins at an angle, allowing the soil aggregates to freely move through the machine until they reached a sieve that they can fit through. The aggregates then drop into the collection pans where they are weighed to find out the Aggregate Size Distribution.

    Another test that I really enjoyed was Texture Analysis. To find soil texture, we used the pipette method by Gee and Dani(2002). In this method, soil is suspended in a water and Sodium hexametaphosphate. The soil is then left to sit on a shaker overnight. In the morning the soil is transferred to a large graduated cylinder where it is left to sit for seven hours. Once the time is up, a sample of the soil suspension is taken using a vacuum pipette and transferred into a beaker. The beaker is then placed in an oven and dried for 12 hours. This beaker can be weighed once dry to find the clay content of the soil. The rest of the soil in the graduated cylinder is then wet sieved and dried. Once dry they are dry sieved and weighed out by size of the sand fractions.Those weights are then put into a spreadsheet that calculates silt, and sand content. The sand silt and clay percentages can then be input into the soil texture triangle shown below.

    Once all of the data was collected it was ran through a wind erosion prediction system called SWEEP. SWEEP is a model that is part of the Wind Erosion Simulation Models(WEPS). SWEEP takes the soil properties that were imputed into the model and predicts the amount of soil loss that could occur in wind erosion events.

    This data is then ran through a Statistical Analysis Software(SAS). This allows us to determine the differences between the treatments. These results help us to understand wind erosion, and how it is effected by different soil properties.

    Results

    Once all of our data was ran through SWEEP and analysed using SAS we could better understand how all of the tests we ran played a part in the big picture.

  • The 0% removal treatment had a significantly lower erodible fraction than the other removal rates, indicating greater erosion potential
  • The plots with more residue cover had a significantly higher water content than those of little or no cover.
  • Saltation threshold velocity decreased as residue removal increased, i.e., as more residue is removed lower wind speeds are required to initiate wind erosion.(below, left)
  • Modeling the data with SWEEP, no wind erosion was predicted for all treatments except for 100% removal. (below, right)
  • Conclusions

  • Removing all residue from the surface does increase the soils susceptibility to wind erosion.
  • Matching removal levels with inherent soil properties and climate minimizes erosion potential.
  • Leaving some residue cover over soil helps preserve soil moisture and add organic matter.
  • Discussion

    The two tables shown above are a great example of inconsistencies with modeling data. The saltation threshold velocity data clearly shows that there is a definite decrease of wind velocity needed to cause erosion at 50% residue removal and above. However, the soil loss predicted in the sweep model only shows soil loss for the 100% removal rate. This can be explained by the unpredictability of weather patters. The threshold velocity measures the soils erodibility in different wind conditions. The soil loss equation in SWEEP takes those velocity measurements and compares them to the weather patterns in the area. Since 100% removal has such a low threshold velocity the probability of experiencing a wind velocity that would cause a wind erosion event is much higher for 100% removal. However, there is a possibility of different weather patterns that would cause erosion events in the future.

    Residue removal is great in moderation. The benefits of using corn stover as a feedstock for biofuels are numerous, but as shown by this study, removing all residue from the soil can pose some issues. This study was done on a small area in west Kansas. Producers that are looking to sell their corn stover to energy companies should consider the type of land that they are dealing with. Moisture, soil type, and local weather patters are just a few factors that need to be considered when choosing a removal rate. If done in the right way, residue removal could be the next big thing in biofuel production. If done in the wrong way, the consequences could be very harmful to soil health. Once wind erosion has occurred, there is no way to get that soil back. Conserving the resources that we have should play a large role when considering options for renewable energy sources.

    About Me

    • My name is Abby Evans, I am a senior at South Dakota State University majoring in Agronomy with a certificate in Agricultural and Environmental Law.
    • I am originally from Ohio City, Ohio, where I grew up on a small grain farm.

    • In my free time I enjoy golfing, swimming, playing tennis, reading, painting, and spending time with my family and friends.
    • When I graduate from college in May of 2015 I hope to join the Peace Corps where I would like to teach sustainable agriculture to communities in West Africa. Upon completion of Peace Corps service I plan to attend graduate school to pursue a masters degree.

    Acknowledgements

    • This material is based upon work supported by National Science Foundation Grant: REU Site: Summer Academy in Sustainable Bioenergy; NSF Award No.: SMA-1062895, awarded to Kansas State University.
    • Yuxin He
    • DeAnn Presley, Associate Professor-Environmental Soil Science and Management, Department of Agronomy, Kansas State University
    • John Tatarko, Soil Scientist, USDA
    • Cathryn Davis

    References

    Gee, G.W., and O. Dani. 2002. Particle-size analysis: Part 4. Physical methods. In Methods of Soil Analysis, 255-293. SSSA Book Series No. 5. Madison, Wisc.: SSSA.

    Summer Experience

    • Moving to a new place is always difficult. When I found out I got the position in the Sustainable Energy REU, I was very excited but also pretty nervous. From day one I knew this was going to be a great summer. Our group of students bonded instantly and we began our journey in Manhattan.
    • When we weren't at work, or at a group function, we spent a lot of time together checking out the area and working out at the recreation center on campus.
    • We took a lot of interesting tours and saw some really cool places.
    • We spent a lot of time exploring Manhattan and taking trips on weekends. One weekend we went to Kansas City to see a Royals game. Over the 4th of July some of us went to Oklahoma. We even rented a cabin on Tuttle Creek Lake for a weekend.
    • This REU was a great experience that I will remember for the rest of my life!