Soil Analysis Pre-Lab Reading v1

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© Luc Bernier [2024] 1 ENVIR SC 1C03 - Lab 5 Soil Analysis in the Field Pre-Assignment Reading Worth: 5% of your final mark Date Assigned: At the start of the lab period, week of April 1 Date Due: By the end of the lab period, week of April 1 Lab Preparation: Preparation is essential for the completion of this lab during the lab period. Students must review the pre-lab reading prior to attending the lab. Lab Materials: To complete the lab during the lab period, you MUST bring with you your pre-lab reading, a pencil, calculator, and eraser. Please wear weather- appropriate clothing. Location: This lab will take place outdoors on McMaster campus . You will meet your TA by President’s Drive behind Bates Residence. See blue star on map below.

© Luc Bernier [2024] 2 Figure 5.1: Map of McMaster University Campus Introduction Soil is a mix of minerals, organic matter, water, and air and is formed through the biological, chemical, and physical breakdown of parent rock material. Soil has an important role in the Earth’s systems as it interfaces between the lithosphere, atmosphere, hydrosphere, and biosphere. Soil is important for the growth of vegetation, for the storage, supply, and purification of water, and as a habitat for many living organisms. There are many different types of soil, each with different mineral compositions and chemical properties. Soil composition is influenced by the parent rock material, weather, and the assemblage of organisms and vegetation living within the soil. In turn, a soil’s composition can affect the type of vegetation that can be supported and the microorganisms that live within it. For this reason, it is important to be able to characterize a soil’s properties.

© Luc Bernier [2024] 3 Determining Soil Colour Soil colour can be used as an indicator of soil composition. A yellow or red colour can indicate the presence of iron oxides while dark brown or black soils can be an indication of high organic matter content. Soil scientists compare soil colours around the world using the Munsell Soil-Colour Charts which identifies soil colour based on hue (specific colour), value (lightness) and chroma (colour intensity). Using Munsell Soil-Colour Charts The Munsell Soil-Colour Chart classifies soil colour based on hue, value, and chroma. • Hue: The hue is identified as a letter symbol where R= Red, YR = Yellow-Red, and Y= Yellow and is preceded by numbers 0-10. As the numbers increase, the soil becomes more yellow and less red. The hue is found on the tab of each colour chart. • Value : The soil value is reported on a numeric scale from 0 to 10, where 0 = black and 10=white. The Value is found on the vertical axis of the colour chart. • Chroma : The soil chroma is also reported on a numeric scale from 0 to approximately 20, where 0= neutral grey. The chroma is found on the horizontal axis of the colour chart. The determined soil colour must be reported using the Munsell Notation . The Munsell notation is reported as: hue value/chroma. For example, a soil with a 2.5YR hue, 4 value, and 2 chroma is reported as 2.5YR 4/2. This represents a ‘weak red’ soil colour. Note: Rarely will the colour of the soil perfectly match the Munsell colour swatches. Find the closest match. Procedure: 1. Using a soil auger, remove a soil sample from approximately 2-3 inches below the land surface. Try to keep your distance from trees so as not to disturb tree roots. 2. Describe your soil sample in the Lab 5 Results Table (which will be provided by your Teaching Assistant), noting any differences in soil with depth, presence of rocks, roots or visible organisms. 3. Place a small subsample of soil on a white piece of paper ( save the rest

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© Luc Bernier [2024] 4 of the soil for the other analyses in this lab ) 4. Compare your soil subsample to the colour swatches in the Munsell Soil- Colour Charts. Try to view your sample in normal sunlight. Note: if your soil sample has changes in colour with depth, you must classify each of the soil colours. 5. Record the soil colour(s) in the Lab 5 Results Table using the Munsell Notation and the interpreted colour. Ex. Munsell Notation : 2.5YR 4/2 Colour Interpretation : Weak Red Determining Soil pH Soil pH refers to how acidic or basic the soil is as measured on the pH scale. Soil pH influences the solubility of minerals and can affect vegetation. Low pH (acidic) soil can result in toxic concentrations of metals such as manganese and aluminum and can also increase the leaching of nutrients such as potassium (K + ). High pH (basic) soil can lead to iron, phosphorus, and manganese deficiencies. The optimum pH range for plant growth is a pH between 6 and 7 (see Table 5.1). Table 5.1: Soil pH and plant growth (adapted from Whiting et. al , 2014) pH Plant Growth >8.3 Too alkaline for most plants 7.5 Potential for iron, phosphorus, and manganese deficiency 7.2 6.8 to 7.2 – ‘Near neutral’ 6.0 to 7.5 – Acceptable for most plants 7.0 6.8 6.0 Potential for nutrient (N, P, K) deficiency 5.5 Reduced soil microbial activity <5.0 Too acidic for most plants, aluminum, and manganese toxicity Procedure: 1. Remove the green cap from the pH test comparator. Make sure the colour chart is in place. 2. Using a scoopula, take a small sample of soil from 2-3 inches below the land surface. If you have already completed the soil colour test, you can use a subsample from the soil auger material. Avoid touching the soil sample with your hands. 3. Fill the test chamber with soil to the ‘fill with soil’ line. Again, avoid

© Luc Bernier [2024] 5 touching the soil with your hands. 4. Holding the green capsule horizontally over the test chamber, carefully separate the two halves of the capsule and pour the powder into the test chamber. Make sure the capsule is completely empty. Place the empty capsule in the waste disposal bag. 5. Using a dropper, add distilled water to the test chamber to the ‘fill with water’ line. 6. Replace the green cap on the pH test comparator, making sure it caps tightly. 7. Shake the pH test comparator vigorously for 10 seconds. Check to make sure the soil, water, and capsule powder is mixed well. 8. Allow the soil to settle and colour to develop for ~ 1 minute. 9. Compare the colour of the solution to that of the colour chart. For best results, avoid viewing your sample in direct sunlight. 10. Record your results in the Lab 5 Results Table. 11. Dispose of the soil in the waste bucket provided. Rinse the comparator thoroughly for the next lab group. Determining Soil Nutrients Soil nutrients refer to the nutrient elements in soil required for plant growth. The primary nutrients are Nitrogen (N), Phosphorus (P), and Potassium (K) because they are required in larger quantities by plants than other nutrients such as sulfur, magnesium and calcium. You will be determining the N, P, and K values of your soil sample using a soil test kit. For nitrogen content the test measures nitrate concentrations (NO 3 ), for phosphorus content the test measures phosphoric acid (P 2 O 5 ) and for potassium content the test measures potassium oxide or potash (K 2 O). An example equivalency chart for the Rapitest Soil Test Kit by Luster Leaf® in ppm (mg/Litre) is shown in Table 5.2. Table 5.2 : Concentrations (in ppm or mg/litre) equivalency chart for Nitrogen (N), Phosphorus (P), and Potassium (K) for the Rapitest Soil Test Kit by Luster Leaf® Nutrient Depleted Deficient Adequate Sufficient Surplus Nitrogen as NO 3 0 ppm 10 ppm 20 ppm 40 ppm 80 ppm Phosphorus as P 2 O 5 5 ppm 10 ppm 20 ppm 50 ppm 100 ppm

© Luc Bernier [2024] 6 Potassium as K 2 O 50 ppm 200 ppm 400 ppm 600 ppm 900 ppm Procedure: 1. Using a dropper, fill the test chamber of the purple Nitrogen comparator with water from the pre-prepared ‘N,P,K Nutrient Test’ water bottle Note: It is important that you avoid disturbing the sediment when removing water from the bottle. Transfer only liquid. 2. Take the appropriate purple coloured capsule and holding the capsule horizontally over the test chamber, carefully separate the two halves and pour the powder into the test chamber. Make sure the capsule is completely empty. Place the empty capsule in the waste disposal bag. 3. Replace the purple cap on the Nitrogen test comparator, making sure it caps tightly. 4. Shake the N test comparator vigorously for 10 seconds. Check to make sure the water and capsule powder is mixed well. 5. Allow the solution to settle and colour to develop for ~ 10 minutes. 6. Compare the colour of the solution to that of the colour chart. For best results, avoid viewing your sample in direct sunlight. 7. Record your Rapitest and ppm Equivalence results in the Results Table. 8. Dispose of the solution in the waste bucket provided. Rinse the comparator thoroughly for the next lab group. 9. Repeat steps 1-8 for Phosphorus (blue comparator and capsule) and Potassium (Orange comparator and capsule). Determining Soil Texture Soil Texture refers to the proportions of sand, silt, and clay found within a soil. See Figure 5.2 for the relative sizes of soil particles. Soil texture can impact aeration, drainage, nutrient- and water-holding capacity, and its workability. The ideal agricultural soil is a loam soil which contains ~40% sand, ~40% silt and ~20% clay. The larger particles of sand provide structural support, aeration, and permeability, while the smaller particles of silt and clay hold nutrients and water.

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© Luc Bernier [2024] 7 Particle Diameter Coarse Sand 0.5 – 1 mm Medium Sand 0.25 to 0.5 mm Fine Sand 0.10 to 0.25 mm Silt 0.002 to 0.05 mm Clay < 0.002 mm Figure 5.2: The relative sizes of sand, silt and clay particles that make up a soil’s texture Soil Textural Triangle Soil Textural Triangle: Soil texture is often determined through mechanical analysis in a lab to find the percentage of sand, silt, and clay particles making up a soil. Once the composition has been determined, a soil textural triangle is used to classify the soil texture (see Figure 5.3).

© Luc Bernier [2024] 8 Figure 5.3: Soil Textural Triangle – A soil textural triangle is used to determine soil texture when a soil’s particle size distribution is known (i.e.: % of sand, silt, and clay). Examples: A soil with 20% sand, 20%, silt, and 60% clay is classified as a clay . A soil with 20% sand, 60% silt, and 20% clay is a silt loam . Soil Texture using the Jar Sedimentation Method Soil texture can be determined several ways, one of which is using the Jar Sedimentation method. This method mixes soil with soap and water, and over time the sediment settles into three different fractions: sand, silt and clay. This is the method that you will be using in the lab when temperatures are below 10ºC outdoors. The method is described below: Procedure: 1. Use the jar labelled ‘Soil Texture’ for this procedure. Do not shake the jar . The soil in this jar was mixed with soap and water and allowed to settle in advance of the lab. The level of the sand, silt and clay layers

© Luc Bernier [2024] 9 were labelled as the sediment settled. You can read more about the sample preparation here . 2. Using a ruler, measure the height of each of the sand, silt, and clay layers as well as the total height of all three layers combined. 3. Determine the percent of sand, silt, and clay using the following formulas: % sand = sand height /total height x 100 % silt = silt height / total height x 100 % clay = clay height / total height x 100 4. Use the soil textural triangle in Figure 5.3 to determine the type of soil. Record your result in Table 5.3 of your lab. Figure 5.4: Jar sedimentation method after settling; layers of sand, silt, and clay are labelled. The height of each layer would be measured to determine the % of sand, silt, and clay.

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© Luc Bernier [2024] 10 COPYRIGHT NOTICE © Luc Bernier [2024] This work the intellectual property of the instructor (unless otherwise noted), and are protected by law under Canada’s Copyright Act . Unless a users’ right in the Copyright Act covers the particular use, students must not publish, post on a public Internet site, sell, rent, or otherwise distribute this work without the instructor’s express permission. If you have questions about fair dealing and your other rights to use works for educational purposes, please contact copyright@mcmaster.ca

Soil Analysis Pre-Lab Reading v1

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