Soil Analysis Pre-Lab Reading v1

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McMaster University *

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1A03

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Jun 18, 2024

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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

© 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

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