Soil ph Teacher Instructions

Transcription

1 Soil ph Teacher Instructions Introduction: This protocol allows students to determine the ph values of soil, using a ph meter or narrow range ph paper, if ph meters are not available. To optimize the effectiveness of this protocol, soil samples should be taken from varying locations with varying conditions. The students will need to record where the soil sample was taken from and the conditions of the site. The students will also need to remove all litter, leaving only the soil. To better track the results, use the chart below. During the 30-minute waiting period, the students will need to share their results (it may be more efficient to duplicate the student data chart on the board or overhead) and review the ph chart below. In addition, this is an opportunity to introduce/review accompanying vocabulary and/or supplemental readings. This protocol can be used in collaboration with the other Soil Physical Characteristics Protocols. Objectives: 1) Predict ph levels. 2) Prepare soil sample for ph testing 3) Identify soil ph Students Required: Groups of four (you can combine tasks if smaller groups are needed) Estimated Time: 3 class periods (Day one 50 minutes, day two 25 minutes, day three minutes) Overview of Tasks: Day One (50 minutes, this works best if done the day prior to the protocol) 1) Divide class into groups of four. 2) Assign the following roles: Lead Researcher: This student is responsible for conducting the student instructions. Recorder: This student is responsible for recording the data. Reporter: This student is responsible for sharing data and collecting classmates results. Collector and assistant: This student is responsible for collecting the soil sample and assisting throughout the student instructions. 3) Read over student instructions as a class. 4) Have students collect soil samples based on Sampling Strategies Instructions.

2 Day Two (25 minutes) 1) Review the day s tasks 2) Use the chart below to make a key of the location of the students soil samples. Place the students soil samples in 100mL beakers and label A through G. You can also add additional comments as needed to the chart. 3) Allow students to follow the student instructions. 4) After students have completed student instructions through step 8, review ph chart, ph values, and the importance of ph values 5) Allow students to share ph values of their soil samples. 6) Make sure the students filter the soil sample as the filtrate will be used for the nitrogen protocol. Day 3 (20-40 minutes) 1) Have the students interpret results and discuss 2) Have students write a lab report using whatever method works best in your class. Optional While reviewing ph chart, you can go over the following vocabulary: ph, soil reaction, acid, basic, alkaline, organic matter, clay, cations, acidity, soluble, toxicity, parent material. Soil Sample Name of Student Site Taken from A B C D E F G H Comments

3 Soil ph Student Instructions Introduction: The proper soil reaction or ph is extremely important to plants because it directly affects the availability of the nutrients needed for the efficient plant growth. Soils that are too acidic or too alkaline do not favor the solution of compounds, and therefore restrict the presence of ions of essential plant nutrients. The soil ph is a result of many factors including, parent material of the soil, organic matter, vegetative growth, and nutrients added. In this protocol, you will be determining the ph value of your soil sample. You will also be making the connection between ph values and the conditions of the soil at your site. Materials: 100 ml beaker Distilled water ph meter or narrow range ph paper Funnel filter paper Stirring device Data sheet Soil sample Procedures: Each group will follow these procedures. You will aggregate your results. Day 1 (50 minutes, note that travel time will vary): 1) Break up into groups of four 2) Each group should assign to the following roles to individual group members: Lead Researcher: student is responsible for conducting the student instructions Recorder: student is responsible for recording the data Reporter: student is responsible for sharing data and collecting classmates results Collector and assistant: student is responsible for collecting the soil sample and assisting throughout the student instructions. See soil sampling strategies protocol. 3) Read over student instructions as a class. 4) Select the study site locations where each group will extract soil. 5) Go to study site(s). 6) Record any observations about the site (e.g. types of plants around, development, soil moisture, amount of leaf litter). 7) Follow the Soil Sampling Strategies Instructions (which can be found at: to collect your soil samples. The collector needs to obtain 2 3 cups of soil. Make sure to record from where the soil came. 8) Your teacher will label your soil samples A through G.

4 Day 2 (25 minutes): 1) Get into your groups and get out your soil sample. 2) Be sure to record your data on the appropriate row on your student data sheet below (soil samples A through G should have been labeled by your teacher). 3) As a group, predict the ph of your soil sample in the space provided on your data sheet. 4) Add 20-40mL of your soil sample to the 100mL beaker and add double the volume of distilled water. 5) Using the stirring device, stir the solution for approximately 5 minutes. 6) Using what is available (ph meter or narrow range ph paper) determine the ph value of your soil sample. Record value on chart. Day 3 (20-40 minutes): 1) Each group should share their findings/data with the class. This should include a site description. 2) Interpret results and discuss. The following questions are designed to help you make meaningful conclusions. a. Which site had the lowest ph? How about the highest ph? b. Do you think the soil ph impacted the surrounding area? (e.g. types of plans present, types of micro organisms present) c. Why should humans care about the soil ph? How does it impact us?

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