Soil Analysis Lab: Sampling, Classification, and Evaluation

AET AP ES – Soil Analysis Lab Portions of this lab were from excerpted 2019 National Math + Science Initiative, Dallas, Texas. All rights reserved. Visit us online at www.nms.org. AP®* is a trademark of the College Entrance Examination Board. The College Entrance Examination Board was not involved in the production of this material. Used with permission. 1 Soil Lab Purpose: Students will sample and classify soil collected from the Academies of Loudoun campus. Students will understand how soils are classified by texture, how soil nutrient levels are assessed, how to analyze a soil triangle, and how to evaluate soil fertility. Objectives: 1. Collect soil sample as instructed during class. 2. Determine soil classification using GIS data. 3. Analyze soil texture based on its qualitative and quantitative physical characteristics. 4. Classify a soil sample by texture using a soil triangle. 5. Determine levels of pH, nitrogen, potassium, and phosphorus in a soil sample. 6. Evaluate the soil’s overall fertility and drainage characteristics. Materials (per group of 3-4 students): • Core sampler • A variety of unknown soil samples (1-quart size bag per group) • Distilled water (1 gal per class) • Ruler • Electronic balance • Plastic cups or weighing trays • Nitrile gloves (optional) • 250 mL beaker • 100mL Plastic Graduated Measuring Cylinder • One plastic spoon • RapiTest soil test kit • Paper towels • Cling Wrap • Masking Tape • Waste soil bucket *Do not dispose of soil in the sink! Use the bucket provided in the classroom to collect waste soil. Background Information: Soils differ greatly in their texture and chemical characteristics, influencing land use decision making. Soil texture determines water availability and permeability, and the pH and nutrient content determines crop-growing potential.

AET AP ES – Soil Analysis Lab Portions of this lab were from excerpted 2019 National Math + Science Initiative, Dallas, Texas. All rights reserved. Visit us online at www.nms.org. AP®* is a trademark of the College Entrance Examination Board. The College Entrance Examination Board was not involved in the production of this material. Used with permission. 2 Soil texture refers to the proportion and size of the soil’s constituent particles and can be determined quantitatively in the lab. It can also be estimated quickly and qualitatively by evaluating the “feel” of the soil in the field. Coarse-textured (sandy) soils: loose and single-grained. The individual grains can be seen readily or felt. Squeezed, when dry in the hand, it will fall apart when the pressure is released. Squeezed, when moist, it will form a cast, but will crumble when touched. Medium-textured (loamy) soils: has a relatively even mixture of sand, silt, and clay. However, the clay content is less than 20 percent. A loam is mellow with a somewhat gritty feel, yet fairly smooth and highly plastic. Squeezed when moist, it will form a cast which can be handled quite freely without breaking. Fine-textured (clay) soils : usually forms very hard lumps or clods when dry and is quite plastic. It is usually very sticky when wet. When the moist soil is pinched between the thumb and fingers it will form a long, flexible “ribbon.” A clay soil leaves a “slick” surface on the thumb and fingers when rubbed together with a long stroke and a firm pressure. The clay tends to hold the thumb and fingers together with its stickiness. Sand is the largest and coarsest of the particles and creates fewer but larger air spaces in the soil. Due to these air spaces, sandy soils usually percolate quickly, drain quickly and hold very little water. They have low fertility due to the low availability of water and their low nutrient levels. Sandy soils feel and sound gritty. Sand particles can easily be seen by the naked eye. Silt can barely be seen with the naked eye. It feels soft and smooth with a flour-like texture. Silt is a medium sized particle with more but smaller air spaces than sand. These air spaces allow for good water availability and fertility. Clay is the smallest of the particles and cannot be seen even when using an ordinary microscope. The particles are multilayered and contain many elements. These soils are sticky in nature and make a long ribbon when rubbed between two fingers. There are many tiny air spaces between the clay particles. The smallness of the spaces causes clay soils to percolate slowly or not at all. Oversaturated clay soils will not percolate at all. While the pore spaces in clay soils are tiny, the total amount of pore space is greater than in any of the other particle types. Clay soils can hold a large quantity of water. Because clay soils can hold water quite well, they allow only slow water movement and contain many elements necessary for plant growth. Soils can be comprised of any mixture of one, two or three of these soil particle types, giving it a unique texture that can be used to classify the soil into one of many different categories, using a Soil Texture Triangle (see figure 2).

AET AP ES – Soil Analysis Lab Portions of this lab were from excerpted 2019 National Math + Science Initiative, Dallas, Texas. All rights reserved. Visit us online at www.nms.org. AP®* is a trademark of the College Entrance Examination Board. The College Entrance Examination Board was not involved in the production of this material. Used with permission. 3 Soil texture is directly related to the percolation rate of a soil in the size of air spaces and surface area of the soil particles. For example, sand is the largest of the soil particles; therefore, it has the largest surface area of the soil particles. Percolation is usually quick in sandy soils. The faster the percolation rate, the more permeable the soil will be (generally). Rate of percolation determines how land can be used. Soils with slow percolation rates would be difficult to drain, causing problems with a septic system, for example. Alterations in the septic system, or of the soil itself, would be required. Soil structure refers to the tendency of soil particles to cluster together and function as soil units called aggregates. Aggregates or crumbs contain mostly clay, silt and sand particles held together by a gel-type substance formed by organic matter. Aggregates absorb and hold water and nutrient better than individual particles, also influencing chemical reactions in the soil. Another major benefit of a well-aggregated soil or a soil with good structure is its resistance to damage by falling raindrops. When hit by falling rain, the aggregate stays together as a water absorbing unit, rather than separating into individual particles. When aggregates on the surface of soil dry out, they remain in a crumbly form and permit good air movement. However, dispersed soil particles run together when dry and form a crust on the surface. The crust prevents air exchange between the soil and atmosphere and decreases plant growth. The process and benefits of aggregation is applicable mostly to fine- and medium-textured soils. Organic matter or humus also plays an important role in soil structure. Soil is a living medium with a great variety of living organisms. Living organisms excrete cell or body wastes which become part of the organic content of soil. Further, the microbes of the soil and the remains of larger plants and animals decompose or decay into soil-building materials and nutrients. People who garden and/or farm generally find it useful to add organic materials to the soil. Popular sources of organic matter for soil amendments are peat moss, leaf mold, compost, livestock manure, sawdust and others. Some important benefits of organic matter in soil include supplying nitrogen and other nutrients to the plants, holding water to protect against drought, furnishing food for soil organisms, minimizing leaching and stabilizing soil structure. Pre-Lab: Take this Soil Practice Test. VA Envirothon Soils Quiz A copy of your test with answers will be emailed to you. 1. What was your score? ________________________________________________________________ 2. What was the hardest question? _______________________________________________________________________________________ _______________________________________________________________________________________ 3. What was the easiest question? _______________________________________________________________________________________ _______________________________________________________________________________________

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AET AP ES – Soil Analysis Lab Portions of this lab were from excerpted 2019 National Math + Science Initiative, Dallas, Texas. All rights reserved. Visit us online at www.nms.org. AP®* is a trademark of the College Entrance Examination Board. The College Entrance Examination Board was not involved in the production of this material. Used with permission. 4 Part 1: Soil Sampling and Preparation 1. Collect the soil sample from the school campus. Draw a vicinity map and identify the sample location as well as possible (e.g., coordinates, approximate distance from building, direction). 2. Remove extraneous top layer leaves, pine needles, sticks, etc. before collecting core sample. 3. Observe your sample before removing it from the sampler. Do you see any layers? Different colors? Write your observations here. _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ 4. Save your sample in a labelled plastic bag for later analysis. Part 2: Soil Classification/Web Survey 1. Go to https://logis.loudoun.gov/weblogis/ 2. Enter the Academies of Loudoun address under the Search tab. 3. Go to the Map tab and toggle on the following under LandRecords. Make sure the main heading is selected in addition to the subheadings. 4. Select the Environment heading and subheadings as shown. 5. Soil Description and Characteristics (may need to check details under the Metadata tab): a. Mapping Unit Number: b. Name: c. Slope: d. Soil Characteristics: e. General Development Potential: Part 3: Qualitative Analysis of Soil Texture 1. Use the spoon to remove 3-4 heaped spoons of soil and place it on a paper towel. 2. Carefully remove as much organic material (leaves, twigs, roots, etc.) as possible, to create a clean soil sample 3. Watch this video Soil Texture Instructional Video

AET AP ES – Soil Analysis Lab Portions of this lab were from excerpted 2019 National Math + Science Initiative, Dallas, Texas. All rights reserved. Visit us online at www.nms.org. AP®* is a trademark of the College Entrance Examination Board. The College Entrance Examination Board was not involved in the production of this material. Used with permission. 5 4. Using the procedure demonstrated in the video and in the flowchart below, evaluate the soil’s texture by “feel”. Figure 1. Source: https://content.ces.ncsu.edu/extension-gardener-handbook/1-soils-and-plant- nutrients .

AET AP ES – Soil Analysis Lab Portions of this lab were from excerpted 2019 National Math + Science Initiative, Dallas, Texas. All rights reserved. Visit us online at www.nms.org. AP®* is a trademark of the College Entrance Examination Board. The College Entrance Examination Board was not involved in the production of this material. Used with permission. 6 Qualitative Analysis Results: 1. What type of soil did the “texture-by-feel” test determine your sample to be? Part 2: Quantitative Soil Analysis 1. Break up any large pieces of your cleaned soil. 2. Fill the graduated measuring cylinder to approximately 30 mL with soil. 3. Slowly add water, up to the 100 mL mark. 4. Place your hand tightly over the top of the cylinder and shake the mixture to break up the larger aggregates (this will take several minutes). 5. After all large pieces of soil have been broken up and suspended, seal the top of the cylinder with cling wrap, and use tape to label your cylinder. 6. Allow the soil columns to settle undisturbed overnight. 7. After 24 hours, measure the height of the soil in the measuring cylinder and record this as “Total Volume” on your data table a. IMPORTANT: if there is still a lot of clay suspended in the liquid above the settled soil, add 1-2 mL to the Total Volume 8. Identify three distinct layers within the cylinder: sand (bottom), silt (middle) and clay (top). 9. Measure the height of each layer (in mL), and record this on your data table a. IMPORTANT: if there is still a lot of clay suspended in the liquid above the settled soil, add 1-2 mL to the total for Clay. 10. Use the following formula to calculate the percentage of each particle size in your soil sample and use the soil texture triangle to determine the soil type: Height of Each Layer / Total Volume ( see #7) x 100 : % Sand: __________ % Silt: ____________ % Clay: ___________

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AET AP ES – Soil Analysis Lab Portions of this lab were from excerpted 2019 National Math + Science Initiative, Dallas, Texas. All rights reserved. Visit us online at www.nms.org. AP®* is a trademark of the College Entrance Examination Board. The College Entrance Examination Board was not involved in the production of this material. Used with permission. 7 Part 3: Chemical Analysis of Soil 1. Follow the directions in the RapiTest Soil Test Kit© to determine the pH, N, P and K levels of the soil sample. 2. Watch this video before conducting your tests: Soil RapiTest Instructions 3. Record the soil sample results in your data table. Soil Texture Triangle Figure 2. Source: http://passel.unl.edu/pages/informationmodule.php?idinformationmodule=1130447039&topicorder=2& maxto=10 .

AET AP ES – Soil Analysis Lab Portions of this lab were from excerpted 2019 National Math + Science Initiative, Dallas, Texas. All rights reserved. Visit us online at www.nms.org. AP®* is a trademark of the College Entrance Examination Board. The College Entrance Examination Board was not involved in the production of this material. Used with permission. 8 To use the triangle, locate the percentage of each particle from your data table. Draw a straight line through each point. Where the three lines intersect is the name of your soil type. Based upon the soil texture triangle above, how would you classify your soil? __________________ Data Table: Analysis Questions: 1. The proportions of what three particles are used to determine soil texture? a. Which of these particles has the smallest surface area? b. Which has the largest surface area?

AET AP ES – Soil Analysis Lab Portions of this lab were from excerpted 2019 National Math + Science Initiative, Dallas, Texas. All rights reserved. Visit us online at www.nms.org. AP®* is a trademark of the College Entrance Examination Board. The College Entrance Examination Board was not involved in the production of this material. Used with permission. 9 2. Using the soil triangle, what “type” is a soil with 20 percent clay, 40 percent silt and 40 percent sand? 3. Explain which method of soil texture analysis you think is more reliable, qualitative or quantitative? 4. Looking at the Soil Texture Triangle (Fig. 2), which soil type would you predict has the greatest and why: a. Water-holding potential? b. Percolation rate? 5. What role does humus play in soil fertility? 6. Why is pH such an important aspect of soil fertility? 7. Explain how Nitrogen, Potassium, and Phosphorus are incorporated/cycled into the soil. Remember your biogeochemical cycles. Nitrogen: Potassium:

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AET AP ES – Soil Analysis Lab Portions of this lab were from excerpted 2019 National Math + Science Initiative, Dallas, Texas. All rights reserved. Visit us online at www.nms.org. AP®* is a trademark of the College Entrance Examination Board. The College Entrance Examination Board was not involved in the production of this material. Used with permission. 10 Phosphorus: 8. Using the provided reference materials and your own research tools, evaluate the fertility of the soil used in this lab activity, based upon each of your chemical test results. What commercial crops, if any, could be grown? What nutrients are lacking? Defend your claims using evidence and reasoning: 9. Evaluate the drainage/water holding characteristics of the soil, based on your results. Use evidence and reasoning to support your claims: 10. List five (5) things you learned about soil and its importance/application to sustainability.

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