Investigating the pH of Soils
Resource ID#: 36341
Primary Type: Lesson Plan
This document was generated on CPALMS - www.cpalms.org
In this activity students will conduct research then test the effects of adding products to soil. Students will learn about soil pH, what factors affect the
pH of soil and how important it is to the growth of plants. Students will learn to use reputable resources to support their findings. Students will be
expected to write a detailed lab report that thoroughly explores the concept while integrating the data from their investigation.
Subject(s): English Language Arts, Science
Grade Level(s): 9, 10, 11, 12
Intended Audience: Educators
Suggested Technology: Computer for Presenter,
Computers for Students, Internet Connection, Probes
for Data Collection, LCD Projector
Instructional Time: 5 Hour(s)
Resource supports reading in content area: Yes
Freely Available: Yes
Keywords: pH, soil, acid, base, alkaline, plants, agriculture, research
Instructional Component Type(s): Lesson Plan
Instructional Design Framework(s): Structured Inquiry (Level 2), Writing to Learn
Resource Collection: Brevard County School District
ATTACHMENTS
pH of Soil Student Data Sheet.docx
LESSON CONTENT
Lesson Plan Template: Guided or Open Inquiry
Learning Objectives: What will students know and be able to do as a result of this lesson?
1. Soil pH is vital to the healthy growth and yield of plants and crops. Numerous factors affect the pH of soil.
2. A basic definition from Wikipedia: "Acidity in soils comes from H+ (hydronium) and Al3+ (Aluminum) ions in the soil solution and sorbed to soil surfaces. While pH is
the measure of H+ in solution, Al3+ is important in acid soils because between pH 4 and 6, Al3+ (aluminum) reacts with water (H2O) forming AlOH2+, and
Al(OH)2+, releasing extra H+ ions. Every Al3+ion can create 3 H+ ions."
3. According to: Charles C. Mitchell from the Extension Agronomist at Auburn University, fertilization with fertilizers containing ammonium or adding large quantities of
organic matter to a soil will ultimately increase the soil acidity and lower the pH.
4. NH4+ + 2O2
bacteria
NO3-+ 2H+ + H2O
5. Soils are limed to reduce the harmful effects of low pH (aluminum or manganese toxicity) and to add calcium and magnesium to the soil.
6. Lime reduces soil acidity (increases pH) by changing some of the hydrogen ions into water and carbon dioxide (CO2). A Ca++ ion from the lime replaces two H+
ions on the cation exchange complex. The carbonate (CO3-) reacts with water to form bicarbonate (HCO3-). These react with H+ to form H2O and CO2. The pH
increases because the H+ concentration has been reduced.
7. H
Soil Colloid + CaCO3
Soil Colloid-Ca++ + H2 O + CO2
H
8. There are ways we can change the pH of soil to reach optimum pH for the type of plant/crop we need.
9. Students will learn how adding different types of ingredients to soil affect the pH and how the pH allows plant processes to occur.
10. They will also learn why this is important not just for a casual gardener, but for agriculture, reducing the amount of chemicals that get added to our soil on a large
scale.
page 1 of 7 11. Other issues related to soil pH includes environmental concerns as far as adding unnecessary chemicals to the soil and how these might affect other organisms and
the water quality in an environment.
12. Students will conduct research on soil pH, identifying at least two reputable sources from their own state. Soil chemistry can vary from different areas.Students will
write a detailed lab report using the IMRAD format. (see attached)
Prior Knowledge: What prior knowledge should students have for this lesson?
SC.5.L.17.1 Compare and contrast adaptations displayed by animals and plants that enable them to survive in different environments such as life cycles, variations,
animal behaviors and physical characteristics.
SC.8.P.8.8 Identify basic examples of and compare and classify the properties of compounds, including acids, bases, and salts.
Guiding Questions: What are the guiding questions for this lesson?
1. What is pH a measure of?
2. How do we measure the pH of soil?
3. What range of pH in soil is optimum for specific plants?
4. How does adding fertilizer and lawn lime affect the pH of soil?
5. What factors contribute to changing pH levels in soil?
6. What are some environmental issues related to soil pH?
7. Can you identify reputable resources that develop your understanding of a topic?
8. What elements are important in a thorough lab report?
Introduction: How will the teacher inform students of the intent of the lesson? How will students understand or develop an
investigable question?
Problem: Soil pH is vital to the healthy growth and yield of plants and crops. Numerous factors affect the pH of soil. There are ways we can change the pH of soil to
reach optimum pH for the type of plant/crop we need.
For this investigation we are going to find out how we can alter the pH of soil.
Follow up will include the how and the why this happens. Students will test different soil enhancements farmers and gardeners use to adjust the pH: calcitized
limestone (lawn lime) and fertilizer (with more than 20% of sulfur).
Students will gain experience using a pH Sensor and learn soil pH measuring technique as you determine the pH of a soil sample.
Investigate: What will the teacher do to give students an opportunity to develop, try, revise, and implement their own methods to
gather data?
Students will conduct preliminary research on soil pH; what factors affect the pH of soil, what are optimum pH levels for specific plants and crops and what can be done
to prepare and adjust soil pH to get the composition you need.
Students will test pH of three different types of soil as a preliminary activity. For follow up extension, students will then design their experiment based on their
questioning.
Materials Needed:
Vernier pH probes with Go Link interface (or use pH strips)
Computers with Vernier Logger Lite installed (if using Vernier probes)
Create the soil samples (make sure to test ahead of time to know what type of range your students will find):
You will need at least 40 mL per sample per group for this preliminary test. Keep an extra bin for each type for clean up. You will be able to use these later when
students conduct follow up activities)
Lawn Lime (calcitized limestone)
Fertilizer (Miracle Gro or similar with at least 20% sulfur)
Soil sample A (Lawn Fertilizer such as Miracle Gro (with at least 20% Sulfur) added to potting soil--make sure to double or triple the recommended amount on the
package to get an exaggerated reading), B (Lawn Lime added to potting soil, again add double or triple the amount recommended to get an exaggerated reading),
and C (Control -General potting soil)
C:
A:
B:
Distilled water
Paper towels
Spoons
Graduated Cylinders (for water)
Measuring cups
Procedure:
Students will conduct research on the computer all about the pH of soil; what factors affect the pH, what is added to soil to adjust the pH and what causes plants to
need pH at a certain level. Students will use only reputable sources to find their information (you should review this with your students--have students help you define
what reputable means in this case). They will need to cite their sources later on in their final lab report.
After the initial research students will summarize their findings. Next up is a lab to test or confirm their preliminary research:
Students can record their preliminary data onto a Google Docs lab form. Teachers can create their own form similar to this one:
http://goo.gl/DfDRb
If not, teachers can create a lab sheet with similar questions.pH of Soil- Student Data Sheet.docx
1. Fill out preliminary questions from online data collection form or on their data sheet.
2. Label 3 cups: A, B and C.
3. Keep a 4th cup about half full of distilled water. You will use this to rinse your pH meter after each test.
4. Place about 40 mL of sample soil into cup--normally you would measure soil on a balance, but for the sake of this experiment you want to find a 1:1 solution of soil
to water in volume (make sure they match your labels!)
5. Pour about 40 mL of distilled water into cup. (you want a 1:1 solution)
6. Stir each sample.
page 2 of 7 7. Plug pH meter into Go Link interface. Plug the USB end into the computer.
8. Open the Logger Lite software (green icon on desktop)
9. The sensor should automatically be detected and should be showing pH.
10. Gently remove pH sensor from buffer solution bottle.
11. Rinse pH meter in distilled water. Keep in water until ready to test.
12. Place pH meter into sample to be tested, Click the green 'Collect' button on the program. Continue taking the reading for about 30 seconds or until the pH stays
constant. Click red 'Stop' when finished.
13. Click 'Store' on the software. This will save your current reading and allow you to continue with the next.
1. Repeat steps 11-14 for next sample.
2. Repeat steps 11-14 for next sample. (Students would then save their Logger lite file)
3. Complete lab data on form: http://goo.gl/DfDRb
4. Clean up by pouring wet soil into appropriate bin. Rinse cups for next group.
5. Pour out distilled water, rinse out pH sensor, replace into buffer solution container.
Write up recommendations based on your findings. (on electronic form)
As a class we review data together to draw conclusions. Relate to possible causes. Ask students to reflect back on what they have learned in history classes about the
great Dust Bowl, the cotton plantations pre-Civil war and how this might relate to our investigation.
Continue this problem investigation with improving soil quality for poor soils in areas where this is a major issue. How often does soil pH need to be tested? What are
the causes and effects of acidic or basic soil?
After completing this lab, students will first use reference sources to find out more about soil pH before they choose and investigate a researchable question dealing
with soil pH.
Some topics to consider in reference search are:
soil pH
soil acidity
soil nutrients
soil components
soil horizons
soil types
buffers
effects of acid deposition on soil
Biology: As part of the unit on studying pH and the activation energy required for biological processes. Plants need the right conditions and elements in order to conduct
the chemical reactions needed to process elements for food and energy. In this case plants need the soil to contain a certain amount of elements that are available for
reactions. However, if the pH of the soil is not ideal, the plants won't have elements necessary for processing. Not all plants need the same soil conditions. Determine
the type of soil optimum for maximum growth.
Chemistry: How the delicate balance of elements are available to activate based on the pH. The availability of iron, copper, phosphorus, zinc, and other nutrients, as
well as the negative effects of various substances, are controlled in large part by soil pH. Some potentially toxic substances in soils, such as aluminum (Al3+) and lead
(Pb2+), have little effect on plant growth under alkaline or basic conditions, but are a serious concern when the same concentrations occur in acid soils. Many nutrients,
especially phosphorus, show their greatest availability in slightly acid to neutral soils, with distinct lower accessibility with increases or decreases in soil pH.
Environmental Science: The balance of using the earth wisely, by not wasting fertilizer and lime if not needed, by rotating crops to restore the required nutrients to the
soil, how education is needed to plant smart. The minimal amount of chemicals necessary to produce healthy crops. Soil pH is an indicator of soil weathering. Soil pH
values reflect the mineral content of the parent material, the length of time and severity of weathering, and especially the leaching of basic materials from the soil
profile. Factors such as the type of vegetation, annual rainfall, and drainage as well as the activities of man also influence soil pH.
Analyze: How will the teacher help students determine a way to represent, analyze, and interpret the data they collect?
The teacher should encourage collaboration and discussion among groups. Check to see what other groups are finding in their tests. Are students receiving the same
results? What would account for the variation?
The reason to use an electronic spreadsheet like Google Docs is so students can see what all others in the class are finding instantly to compare their results. It is
important for teachers to make students feel comfortable enough with their data to not change their data to more closely match others in the class, but if they are
finding something different to figure out or ask for assistance to see what the difference might be caused by.
Students will be answering the following post lab questions:
For the following questions conduct research to check for crops in your region that would grow best in these pH levels. Make sure you find two reputable sources government or university sites.
1. From this test, what crops would grow best in soil sample A?
2. From this test, what crops would grow best in soil sample B? From this test, what crops would grow best in soil sample C?
3. From this test, what does sulfur seem to do to the pH of the soil?
4. From this test, what does limestone seem to do to the pH of the soil?
5. How does pH relate to aluminum toxicity in the soil?
6. What is the main chemical in limestone? How does limestone change the pH of the soil?
7. Summarize your findings in written form. Make sure to include excerpts from your research to support your findings.
Closure: What will the teacher do to bring the lesson to a close? How will the students make sense of the investigation?
1. Ask students to share their findings with the class. Discuss and find a consensus. Have students identify their sources. Did any students find sources that were
contradictory? What should we do when we find this? How can you guarantee the information you find is accurate? --Students should conclude that the source
page 3 of 7 should be from a research site if at all possible, if not look to see if a site at least sites their source such as Wikipedia.
2. This lesson might lead to further study depending on your class. Students might begin a series of plant growing experiments, or soil chemistry experiments
examining the effectiveness of plant enzymes in different pH levels. Students might start a school garden, hydroponics, or other type of exploration with plants.
Summative Assessment
1. Students will be able to explain what adding fertilizer or lawn lime to soil will do to the soil, what this means for plants, and how adding these chemically affects the
pH of the soil. Students will explain how the science of soil is an important issue in agriculture, environmental science, and/or the possibility and issues involved in
growing plants on other planets or moons such as Mars.
2. Student IMRAD formatted lab reports will include explanations of what this all means.
3. Student IMRAD lab reports will include research articles that support their findings. They will printout their research findings, highlight where in the article it
reinforces their results and supports their explanation.
IMRAD Lab Report Template.docx
Formative Assessment
1. Review understanding of pH. At this point most students will recall that items with a pH of less than 7 are an acid and those above 7 are a base. As we get into the
more scientific understanding: the number of hydronium ions in solution, regular questioning of the students will help the teacher see if students are processing the
information.
2. Read a research article together relating to pH of soil, asking students to share what they understand from the reading. Students will discuss what this might mean
and how it relates to our problem that we will be investigating.
3. As students are working on their investigation/lab experiments, ask students to explain:
pH and how does it relate to the health of the soil or the growth of plants in the soil.
how pH affects the ability of plants to take in other minerals
how pH of the soil allows some chemicals such as aluminum to become toxic to plants
If they aren't able to answer these questions, guide them by questioning, reminding them of what had been previously discussed in class or lead them to articles on
these topics. Review with students the importance of reliable research.
4. Give students examples of articles (news sources, government sites and others) and ask students whether these resources are reputable.
5. Get the students to decide/agree together what types of research are to be used in this project.
6. Review the IMRAD Lab report format for this project (attached). Go over each section with students if this is the first time using this type of format and ask students
to clarify how they could complete each section or what it might look like.
7. Review the IMRAD Rubric with students asking for students to describe what each criteria might include.
Feedback to Students
1. The teacher should rotate through each group questioning students about what they are finding, and asking them to explain what is causing their readings. If
students are confused the teacher should guide their understanding through questioning to lead them back to an understanding.
2. While students are reading and discussing the research articles, the teacher will question students on how this relates to their experiment. If students are having
trouble making connections the teacher will ask students questions to direct them to the connections.
ACCOMMODATIONS & RECOMMENDATIONS
Accommodations:
1. Students will be working in lab groups.
2. The teacher can assign students to work together based on their needs and abilities.
3. The teacher will circulate frequently to make sure all members are participating and contributing to the group.
4. Students needing extra help with the research portion will be given special attention.
5. A teacher could provide those students with a list of pre-determined websites students can use to get them started.
6. The teacher could also screen the reading level of the websites to ensure they aren't too high level for some low readers.
Extensions: As a class we review data together to draw conclusions. Relate to possible causes. Ask students to reflect back on what they have learned in history
classes about the great Dust Bowl, the cotton plantations pre-Civil war and how this might relate to our investigation.
Continue this problem investigation with improving soil quality for poor soils in areas where this is a major issue. How often does soil pH need to be tested? What are
the causes and effects of acidic or basic soil?
After completing this lab, students will first use reference sources to find out more about soil pH before they choose and investigate a question dealing with soil pH.
Some topics to consider:
soil pH
soil acidity
soil nutrients
soil components
soil horizons
soil types
buffers
effects of acid deposition on soil
Integrated Science/General Science: As part of a unit in studying pH, investigate real world examples where pH is vital to industry. In the case of farming, measuring the
pH of soil is crucial.
Identifying plants that grow in different pH levels of soil.
Adaptations of plants in dry arid conditions--how that affects the pH to the soil, to a rich, wet soil, to mostly clay soils, etc...
Biology: As part of the unit on studying pH and the activation energy required for biological processes. Plants need the right conditions and elements in order to conduct
page 4 of 7 the chemical reactions needed to process elements for food and energy. In this case plants need the soil to contain a certain amount of elements that are available for
reactions. However, if the pH of the soil is not ideal, the plants won’t have elements necessary for processing. Not all plants need the same soil conditions. Determine
the type of soil optimum for maximum growth.
Chemistry: How the delicate balance of elements are available to activate based on the pH. The availability of iron, copper, phosphorus, zinc, and other nutrients, as
well as the negative effects of various substances, are controlled in large part by soil pH. Some potentially toxic substances in soils, such as aluminum (Al3+) and lead
(Pb2+), have little effect on plant growth under alkaline or basic conditions, but are a serious concern when the same concentrations occur in acid soils. Many nutrients,
especially phosphorus, show their greatest availability in slightly acid to neutral soils, with distinct lower accessibility with increases or decreases in soil pH.
Environmental Science: The balance of using the earth wisely, by not wasting fertilizer and lime if not needed, by rotating crops to restore the required nutrients to the
soil, how education is needed to plant smart. The minimal amount of chemicals necessary to produce healthy crops. Soil pH is an indicator of soil weathering. Soil pH
values reflect the mineral content of the parent material, the length of time and severity of weathering, and especially the leaching of basic materials from the soil
profile. Factors such as the type of vegetation, annual rainfall, and drainage as well as the activities of man also influence soil pH.
References and Resources:
Using the Vernier pH sensor:
http://www.vernier.com/innovate/measuring-the-ph-of-soil-with-the-new-tris-compatible-flat-ph-sensor/
For Middle School Science:
http://edibleschoolyard.org/resource/soil-ph-lab
http://www.eutechinst.com/techtips/tech-tips6.htm
For Regular High School and Integrated Science Classes:
http://www.garden.org/foodguide/browse/veggie/tomatoes_getting_started/358http://www.nc
For Honors Classes and AP:
http://courses.nres.uiuc.edu/nres201/Labs/NRES%20201%20Lab%209(2008).pdf
http://www.css.cornell.edu/courses/260/Dynamic%20Soil%20Systems%20Part%20A.pdf
http://www.clemson.edu/sera6/Soil%20pH%209-23-041.htm
ncagr.gov/cyber/kidswrld/plant/nutrient.htm
UF/IFAS:
http://solutionsforyourlife.ufl.edu/hot_topics/agriculture/soil_testing.html
The Globe Program:
http://www.globe.gov/home
Pelletized Limestone:
http://www.homedepot.com/catalog/pdfImages/94/9451906b-f7a2-45d5-b731-21ec2f6369f5.pdf?cm_mmc=seo|altruik|100348791
Miracle Grow Fertilizer:
http://www.homedepot.com/catalog/pdfImages/f1/f157cb99-d050-45ea-a721-a63753286c91.pdf
Suggested Technology: Computer for Presenter, Computers for Students, Internet Connection, Probes for Data Collection, LCD Projector
Special Materials Needed:
Vernier or Pasco data loggers or similar. If not available, pH testers or soil test strips.
Vernier Logger Lite software (this is a free download) if using Vernier pH meters
Google Docs accounts for students if using Google Docs for a collaborative spreadsheet. If not available you can use one computer station for students to record the data
that can then be projected for the class to see.
Other materials:
1. Soil sample A, B, and C
2. Distilled water
3. Lawn Lime (calcitized limestone)
4. Fertilizer (Miracle Gro or similar with at least 20% sulfur)
5. Paper towels
6. Spoons
7. Graduated Cylinders (for water)
8. Measuring cups
Additional Information/Instructions
By Author/Submitter
SOURCE AND ACCESS INFORMATION
page 5 of 7 Contributed by: Maggie Molledo
Name of Author/Source: Maggie Molledo
District/Organization of Contributor(s): Brevard
Is this Resource freely Available? Yes
Access Privileges: Public
License: CPALMS License - no distribution - non commercial
Related Standards
Name
LAFS.910.RST.1.1:
LAFS.910.RST.3.8:
LAFS.910.RST.3.9:
Description
Cite specific textual evidence to support analysis of science and technical texts, attending to the precise details of
explanations or descriptions.
Assess the extent to which the reasoning and evidence in a text support the author’s claim or a recommendation for
solving a scientific or technical problem.
Compare and contrast findings presented in a text to those from other sources (including their own experiments),
noting when the findings support or contradict previous explanations or accounts.
Define a problem based on a specific body of knowledge, for example: biology, chemistry, physics, and earth/space
science, and do the following:
1. Pose questions about the natural world, (Articulate the purpose of the investigation and identify the relevant scientific
concepts).
2. Conduct systematic observations, (Write procedures that are clear and replicable. Identify observables and examine
relationships between test (independent) variable and outcome (dependent) variable. Employ appropriate methods for accurate and
consistent observations; conduct and record measurements at appropriate levels of precision. Follow safety guidelines).
3. Examine books and other sources of information to see what is already known,
4. Review what is known in light of empirical evidence, (Examine whether available empirical evidence can be
interpreted in terms of existing knowledge and models, and if not, modify or develop new models).
5. Plan investigations, (Design and evaluate a scientific investigation).
6. Use tools to gather, analyze, and interpret data (this includes the use of measurement in metric and
other systems, and also the generation and interpretation of graphical representations of data,
including data tables and graphs), (Collect data or evidence in an organized way. Properly use instruments,
equipment, and materials (e.g., scales, probeware, meter sticks, microscopes, computers) including set-up,
calibration, technique, maintenance, and storage).
7. Pose answers, explanations, or descriptions of events,
8. Generate explanations that explicate or describe natural phenomena (inferences),
9. Use appropriate evidence and reasoning to justify these explanations to others,
10. Communicate results of scientific investigations, and
11. Evaluate the merits of the explanations produced by others.
Remarks/Examples:
Florida Standards Connections for 6-12 Literacy in Science
For Students in Grades 9-10
LAFS.910.RST.1.1 Cite specific textual evidence to support analysis of science and technical texts, attending to
the precise details of explanations or descriptions.
SC.912.N.1.1:
LAFS.910.RST.1.3 Follow precisely a complex multistep procedure when carrying out experiments, taking
measurements, or performing technical tasks attending to special cases or exceptions defined in the text.
LAFS.910.RST.3.7 Translate quantitative or technical information expressed in words in a text into visual form
(e.g., a table or chart) and translate information expressed visually or mathematically (e.g., in an equation) into
words.
LAFS.910.WHST.1.2 Write informative/explanatory texts, including the narration of historical events, scientific
procedures/ experiments, or technical processes.
LAFS.910.WHST.3.9 Draw evidence from informational texts to support analysis, reflection, and research.
For Students in Grades 11-12
LAFS.1112.RST.1.1 Cite specific textual evidence to support analysis of science and technical texts, attending to
important distinctions the author makes and to any gaps or inconsistencies in the account.
LAFS.1112.RST.1.3 Follow precisely a complex multistep procedure when carrying out experiments, taking
measurements, or performing technical tasks analyze the specific results based on explanations in the text.
LAFS.1112.RST.3.7 Integrate and evaluate multiple sources of information presented in diverse formats and
media (e.g., quantitative data, video, multimedia) in order to address a question or solve a problem.
LAFS.1112.WHST.1.2 Write informative/explanatory texts, including the narration of historical events, scientific
procedures/ experiments, or technical processes.
LAFS.1112.WHST.3.9 Draw evidence from informational texts to support analysis, reflection, and research.
Florida Standards Connections for Mathematical Practices
MAFS.K12.MP.1: Make sense of problems and persevere in solving them.
MAFS.K12.MP.2: Reason abstractly and quantitatively.
page 6 of 7 MAFS.K12.MP.3: Construct viable arguments and critique the reasoning of others. [Viable arguments include
evidence.]
MAFS.K12.MP.4: Model with mathematics.
MAFS.K12.MP.5: Use appropriate tools strategically.
MAFS.K12.MP.6: Attend to precision.
MAFS.K12.MP.7: Look for and make use of structure.
MAFS.K12.MP.8: Look for and express regularity in repeated reasoning.
Identify sources of information and assess their reliability according to the strict standards of scientific investigation.
SC.912.N.1.4:
Remarks/Examples:
Read, interpret, and examine the credibility and validity of scientific claims in different sources of information, such
as scientific articles, advertisements, or media stories. Strict standards of science include controlled variables,
sufficient sample size, replication of results, empirical and measurable evidence, and the concept of falsification.
Florida Standards Connections: LAFS.910.RST.1.1 / LAFS.1112.RST.1.1.
Relate acidity and basicity to hydronium and hydroxyl ion concentration and pH.
SC.912.P.8.11:
Remarks/Examples:
Use experimental data to illustrate and explain the pH scale to characterize acid and base solutions. Compare and
contrast the strengths of various common acids and bases.
page 7 of 7