A step-by-step lab demonstration shows soil mixed with distilled water in a test tube, then tested with litmus paper to determine pH. The animation explains what soil pH means, how hydrogen and hydroxyl ion concentrations create acidic or alkaline conditions, and how the 1-14 pH scale is read. On-screen Chichewa text complements English narration. Useful for secondary agriculture students and teachers introducing soil nutrient status and its link to crop growth.
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This is an Agricultural lesson. Explain with animation at each stage. In the experiment use animation of testutube, soil and adding distilled water and litmus paper to show the whole process of testing for PH. Use this information to start explaining what soil pH is and why it is important to know this for crop production. Use animation for each explanation to help students understand. Use Chichewa explanations on screen to compliment the English audio.-Nutrient Status of the Soil Introduction: Soil contains different types of nutrients. The amounts and types of nutrients found in the soil determine the soil status of the soil. Tip You will notice that crops grow with different growth rates on different soils. This could be due to the differences in soil status. Soil is a major source of nutrients to support plant life. The more nutrients the soil has, the more the plants grow. Soil pH is determined by measuring the concentration of hydrogen ions ( H + ) and the hydroxyl ions ( O H - ) in the soil solution. When the soil contains alot of hydrogen ions, the soil is said to be acidic. Whem the soil contains alot of hydroxyl ions, the soil is said to be alkaline of basic. The pH scale is used to determine the level of acidity or alkalanity of the soil. A pH scale has a set of numbers from 1 to 14. Refer to the image below. Take note that the pH value from 1 to 6 tells you that the soil is acidic. The PH vale from 8 to 14 tells you that the soil is alkaline and a pH value of 7 tells you that the soil is neutral A pH value of 1 on the pH scale shows that the soil is highly acidic meaning it contains higher concerntration of hydrogen ions. The pH value 6 means the soil is less acidic meaning it contain less concentration of hydrogen ions. The value 8 on pH scale tells you that the soil is less alkaline and the value 14 tells you that the soil is highly alkaline. he image is telling you three ways of how you can measure soil pH. 1. Blue or Red litmus paper 2. Universal indicator and 3. using a pH meter Measuring soil pH using blue and red litmus paper When you intend to measure soil pH you should arrange to have the following materials. Blue and red litmus paper Barium sulphate powder Soil sample Tin or beaker Stirrer Distilled water This is the procedure that will direct you on how to measure the pH of your soil using litmus paper Put soil sample into tin or beaker Add some distilled water to the soil sample then stir Add an equivalent amount of barium sulphate to the test tube containing the soil (this helps to split the individual soil grains) Dip a blue litmus paper into a solution above and make observations Dip a red litmus paper into a solution and make observations Expected results Once the colour of blue litmus paper changes from blue to red upon dipping it in a soil solution then the soil is said to be acidic. On the other hand when the colour of red litmus paper turns blue upon dipping it in a soil solution then the soil is alkaline. Measuring soil pH using universal indicator solution When you want to measure the pH of your soil sample using universal indicator solution you must arrange the following materials and apparatus Universal indicator Soil sample Test tubes Barium sulphate powder Distilled water Here is the procedure to belfollowed Place a soil sample in a test tube to a height of about 1 cm Fill the test tube with distilled water to about 4cm from he top and shake the test tube thoroughly Add an equivalent amount of barium sulphate to the test tube containing the soil (this helps to split the individual soil grains) Allow the contents of the test tube to settle then add 4-8 drops of universal indicator solution Shake the test tube well and allow contents to settle Hold the test tube against the printed colour chart and note the pH of the colour which matches it mostly Measuring soil pH using the pH meter A pH meter is a device that is used to measure the concentration of hydrogen ions. In the soil. It has two electrodes which are dipped in the soil solution. The digital meter will give the value of the pH of that soil solution. The pH meters are mostly found in agricultural laboratories and are expensive to buy. The image below shows a pH meter measuring the pH of a soil sample note-hi Soil pH is a measure of acidity or alkalinity of the soil. It is determined by assessing the concentration of hydrogen and hydroxyl ions in the soil. Soil containing more hydrogen ions than hdyroxyl ions is said to be acidic. Soil containing more hydroxyl ions than hydrogen ions is said to be an alkaline soil. Soil pH is measure using litmus paper, univesal indicator and pH meter. Audience: middle schooler