CSS205 Service Learning Project Soil-pit Maintenance and Deep Immersion Learning B - Sunday, October 2nd 12-4pm

Soil Pit Maintenance and Deep Immersion Learning: Group B

Project Description: You will learn about soils close-up in a small team with Dr. Jay Noller at the helm. You will be participating in the annual maintenance of our soils teaching pits and will get dirty. You will learn more than you ever thought possible! Tools provided.

Mission: To learn about and maintain soil teaching pits for the benefit of students and researchers in the Department of Crop and Soil Sciences.

Goals:

• Think about various factors that affect erosion of soil pits
• Think about the overland flow of water near the pit focusing on how proximity of the road affects the pit
• Dig into the side of the pit to build the terrace
• Dig windows into the sides of the pit to make analysis of horizons easier

Group Members:

• Natalie Allen
• Nathan Azevedo
• Ryan Forsyth
• Robert Hoffman
• Matt Pittam
• Vince Taylor

I. Connecting With The Soil

On October 2nd, 2011, we traveled back in time more than 70,000 years.  Along the way we witnessed epic floods, huge icebergs, and thousands of years of human history.  Our guide Dr. Jay Noller showed where the icebergs melted and left "kettle holes" the size of a football field.  He also illustrated the effect of three series of floods that occurred around 70,000, 40,000 and 15,000 years ago.  The most remarkable fact about our trip however, was the design of the vessel that we traveled in.  Most people would call it a hole in the ground.

We were exploring two of Oregon State University's "soil pits."  A soil pit is, indeed, a hole in the ground.  However, if you know what you are looking at it can reveal many of the events and activities that have taken place in that area throughout human history and beyond.  OSU uses the pits to teach hundreds of students per year how to study the soil.  Our team was in the pits to wage a battle against erosion.  Any time you dig a hole in the ground, Mother Nature does her best to fill it back up again.

The first pit was in Hyslop Field.  This pit had some "tile drainage" in place to keep it from filling with water from the bottom.  However, it was also built next to a road which funnelled water in from the top.  Our job was to build a "terrace" to keep that side of the pit from caving in.  The second pit was in Oak Creek.  Our job in this pit was to cut "windows" into the walls to make the soil horizons easier to view.

II. How Does Soil Make This Project Work?

Why do we use soil pits to learn about soils?

Soil pits are dug by soil scientists, researchers, and students for several reasons. Soils are a four dimensional complex habitat, and studying them from the surface yields only a fraction of the wealth of information contained within. By digging a soil pit we are able to expose a window to the soil horizons within a given sol profile. Every soil on the planet exhibits a different soil profile, and thus different soil horizons with different physical, chemical, and biological properties. However, the horizons in all soils share some similar characteristics, and form as the result of similar processes based on five factors.

Characteristics of Soil Horizons:

• Variable thickness across the soil profile
• Generally oriented parallel to the ground surface
• Uppermost horizons exhibit the most change
• Lowermost horizons are the most similar to the soil’s parent material 

Processes Influencing the Formation of Soil Horizons:

• Physical weathering
• Biogeochemical weathering 

Five Factors Influencing the Formation of Soil Horizons:

1.  Parent Materials
2.  Climate
3.  Biota
4.  Topography
5.  Time 

These characteristics and processes result in the formation of soil horizons within a profile that can be generally categorized from top to bottom as the O, A, E, B, and C horizons. Depending on the extent of the processes described above and the influence of the five soil forming factors, some of the horizons may or may not be present. The figure below shows all of the generalized soil horizons that one might find when excavating a soil pit. The figure also indicates the type of material that one can expect to find in each soil horizon.

Image From: The American Farmer

The two soil pits that we visited for out project were both dug within the Woodburn soil series. Woodburn soils are an extensive series of silt loams that occur throughout the Willamette Valley. The soil pit at Hyslop Farm is characteristic of Woodburn soils on 0-3% slopes, and the soil pit near Oak Creek is characteristic of Woodburn soils on 3-12% slopes. The following describes a typical Woodburn soil profile based on the horizons presented above, and includes details characteristic of all Woodburn soils.

The following photos show the actual profiles from the two soil pits that we performed maintenance on. Just because the general soil profile above shows the typical horizons found in Woodburn soils, it does not mean that you will always find them all represented at every site. 

Hyslop Farm Soil Pit:

Oak Creek Soil Pit:

Terracing To Prevent Erosion:

Soil erosion is a natural process that involves the transport of materials via wind, water, ice, or gravity downslope. Certain amounts of erosion are normal and healthy for ecosystems, and are closely linked to processes within the hydrologic cycle, and in the formation of soil (pedogenesis). However, excessive amounts of erosion due to anthropogenic (human) influences can be detrimental due to the loss of soil, river sedimentation, and the transport of harmful toxins. Typically, when humans alter the natural landscape through actions such as vegetation removal, land use change, and road building the likelihood of increased erosion becomes a reality. The following video shows how large amounts of soil can be moved quickly during the erosion process. 

Soil Erosion After Rain. YouTube. LiveSoaresSeverino. September 1, 2006

Terracing is a soil conservation practice used to prevent erosion. When rainfall is allowed to run unchecked down an un-vegetated slope it will pick up and move loosely aggregated portions of the soil and transport them downward with the power of gravity. This process is characterized by backcutting of the slope being eroded, and the accumulation of sediment at the base of the slope. Terraces are highly effective for reducing erosion by increasing the amount of rainfall that soaks into the ground, therefore preventing overland flow of water and sediment down a slope. In fact, during a terracing study of four watersheds by Spomer et. al. in 1972, it was found that terraced hillslopes changed both the path that water flowed downslope, and the amount of erosion that occurred. In the study all of the watersheds experienced the same amount of water yield annually (7 inches). However, in the terraced fields the water yield was primarily base flow (through the soil), whereas in the un-terraced fields it was surface runoff.  Furthermore, the study indicates that the amount of soil eroded on un-terraced watershed was orders of magnitude greater than on terraced watersheds. During the study period from 1964 – 1970 the un-terraced watersheds averaged 25 tons per acre per year of eroded sediment while the terraced watersheds averaged only 3. (Spomer et al. 1973)

The practice of terracing was first developed in agriculture, and is thousands of years old. The exact origin of the practice is unknown, but many cultures have employed the practice including the Babylonians, the Inca, and groups from Southeast Asia. While typically used on a large scale for agriculture, the benefits of terracing are equally valid for modern landscape design, or even soil pit maintenance. The first image below shows a traditional terraced landscape used in Asia for the cultivation of rice. Without the terraces it would be impossible for farmers to flood their rice paddies annually during harvest. 

Image From: Destination 360

This image shows the use of terraces to create landscaping beds on a steep hill. Without the terraces there would not be enough soil on the hillslope to plant trees, flowers, and shrubs.

The following images show the terraces constructed in the Hyslop soil pit. Without these terraces to prevent erosion, backcutting of the slope would have eventually reached the road behind the soil pit, and washed it down the slope. 

References:

Spomer, RG. Shrader, WD. Rosenberry, PE. Miller, EL. 1973. Journal of Soil and Water Conservation, Vol. 28, No. 3.  http://www.ars.usda.gov/sp2UserFiles/Place/36221500/cswq-t1792-spomer.pdf

The American Farmer. Agriculture and Soil Management. http://wisander.wordpress.com/agriculture-and-soil-management

Destination 360. Banaue Rice Terraces. http://www.destination360.com/asia/phillipines/banaue-rice-terraces

III. Possible Improvements via Soil Management

Just finishing the terrace

One of the major problems with the first soil pit we visited was erosion. The problem was that so much erosion had occurred that it was starting to wash away part of the pit wall and take out the edge of the road. In order to remedy this problem we built a terrace along the pit wall next to the road. The purpose of the terrace was to prevent water runoff from washing away more soil and therefore keeping the road intact.

A drain tile leading right into the soil pit

Dr. Jay Noller looking up at our new terrace

The second pit however was extremely over grown by vegetation. In order to remedy this problem we cut and dug out some of the surrounding vegetation and created windows so small groups of students could look at the soil horizons.

Soil Pit 2

Different types of soil management have the potential to improve this project and the longevity of the soil pits in a number of different ways. One way that our team thought of was to test out different methods for preventing erosion. A few possibilities include planting shrubbery or ground cover around the edges of the pit to help hold the soil in place, or creating wind breaks to help reduce the chance of wind moving the soil during the drier seasons. One that seemed the most practical to our group for the first soil pit was to construct surface runoff barriers. This method involves building small walls with bricks or stones to help keep surface water runoff from running into the pits. Both pits had drain tiles around them however we noticed that they seemed to be running into the pits which seemed to be counterproductive because the drain tiles would be collecting water from the surrounding area and draining it into the pit. Extending the life of a soil pit could be achieved in a number of ways some of which we have mentioned above a few other options are to put in temporary shoring when the pit is not in use to help prevent filling in, another option would be to build the pit in a controlled environment to help regulate precipitation, runoff and vegetation. We also thought it would be interesting to see how man affects soil so in order to do this we came up with the idea to modify half a soil pit by farming, fertilizing, or adding organic matter while the other half of the pit is left untouched. Although this could take a few years for future students to be able to see the affects we feel that it would be extremely beneficial to this project.

IV. What Did We Learn?

Erratic

Well hotdog, what didn’t we learn!  Our team went on an exploration of the soil-pits and came away with a plethora of knowledge ranging from kettle holes to plant roots.   Our journey of learning began with an introduction to the history of the soil formation in Willamette Valley.  The richness and the productiveness of the Willamette Valley are indebted to long history of flooding.  There are nearly 40 recorded floods that have flowed through the valley.  Our team was able to see evidence of the last three floods in distinct horizons of each soil-pit.  The most recent flood dating back 15,000 years ago is the well-known Missoula flood, which has had a huge impact on the valleys productiveness.  The former glacial Missoula Lake gushed out water toward the Pacific Ocean and swept away the rich Washington top-soils down the Columbia River Gorge.  Yet, before reaching the Pacific Ocean the waters were redistricted and backed up into the Willamette Valley. The sediment rich waters and large chucks of glacial ice settled in the valley.  It took about two weeks before the waters drained, leaving 3-5 inches of rich pulse.  The large fragments of transported ice sunk into the soil and made hug depression known as kettle holes.  Evidence of flooding was seen at both soil-pit sites and we even identified pieces of an erratic transported from the flood. 

Soil-pit 1

The A horizon is approximately 15, 000 years old and has a sharp clear boundary, illustrating evidence of plowing, thus making the horizon an Ap horizon.  Horizon B has an age of 40,000 years with an enrichment of clay, making it a Bt horizon. Finally, we have a C horizon dating back 70, 000 years.    

V. Broader Impact

The broader impact of soil pit maintenance is entirely centered upon education. Soil pits are used around the world to educate people ranging from farmers, professors, engineers, and students like us.

For example, programs like the soil science program at OSU have been using soil pits to develop the minds of young soil scientists, farmers, and engineers.  Soil pits give students a hands on opportunity to learn about the soil profile, horizons, texture, color and view the importance of soil factors like porosity, bulk density, chemical composition, and water storage capacity. But students aren’t the only ones learning about soil. Professors and researchers from around the world use soil pits for producing soil surveys, conducting studies on soil management, moisture retention, drainage, and determining the soils role as a habitat and its effect on the surrounding environment. Engineers also use soil pits to evaluate soils for future landscape projects and to determine the soils limitations and capabilities concerning their construction projects. Lastly, farmers use soil pits to learn about the growth of your food. Farmers dig pits to monitor soil productivity, examine roots and compaction, and to determine the nutrients and water available to their crops. For instance an article titled “Dig Soil Pits To Assess Strip-Tilled Fields” talks about digging soil pits to see if roots are developing or being stopped by tractor and till caused compaction

VI. Soil Maps and Aerial Photographs

Oak Creek Area of Interest:

Bashaw makes up the majority of the soil in this AOI, at 25.7% for flooded 0 to 3% slopes and 25.7% for nonflooded 0 to 3% slopes, other major components including Woodburn, Amity, Concord, Holcomb, Helmick, and Willamette making up the remainder. Bashaw is a Very-fine, smectitic, mesic Xeric Endoaquerts. It’s parent material is clayey alluvium derived from basalt. Primary uses include growing spring grains, and pasture. Sedges, rushes, grasses, scattered ash, willows, and other trees and shrubs are the natural vegetation. It is frost-free for 165 to 210 days with an annual precipitation of 40 to 60 inches.

Hyslop Farm Area of Interest:

Woodburn Silt Loam is a fine-silty, mixed, superactive, mesic Aquultic Argixerolls. It comes from a parent material of Silty glaciolacustrine deposits. This is the primary soil series making up over 90% of our AOI. It is a moderately drained non-flooding soil, used for growing berries, orchards, cannery crops, grain, hay and pasture land. Native vegetation is Douglas-fir, oak, and grass. Mean annual precipitation is 40 to 50 inches, with a frost-free period of 165 to 210 days.

Conclusion

The goal of Deep Immersion was learning about soil close-up. Getting dirty is a great way to learn about soil and really understand the differences between the various soil horizons. This project involved thinking about how water flows through the area around the pits, and what impacts this has on the pits. The purpose behind the project was digging into the soil and building a terrace to help prevent erosion of the walls of the soil pits. This prevents the road from washing into the pit and allows the pit to continue to be used as a valuable resource for learning about soils.