Soil Fertility Analysis

Soil Fertility Analysis



Purpose:

Four variables are important in determining how fertile soil is. The variables are pH, Nitrogen, phosphorus, and potassium. The goal of the lab was finding the amount of each variable that was present in the soil.

pH Test

By testing the pH of the soil, the sweetness our sourness of the soil can be determined. The pH of the soil sample can tell how how acidic or basic the soil is.  Lower ranges reflect a high acidity level, and higher ranges reflect a higher base level.

Procedure

Materials: Test tubes, caps, a timer, pH indicator, 0.5 g spoon, soil sample

1. pH indicator was poured into the test tube to the 4 mark.
2. A 0.5 gram spoon was used to add three measures of the soil sample.
3. The test tube was capped and mixed gently for one minute.
4. The test tube stood for 10 minutes for the soil sample to settle.
5. The color of the sample was matched to the pH scale.
6. The results were determined.

Observations

• The color of the solution was purple.  
• The color of the sample changed color within the 10 minute time period. 

Phosphorous Test

Materials: All materials were the same as the pH test, except for the addition of a Phosphorus indicator, a pipette, a Phosphorus Test Tablet, a Phosphorus Extract Reactant, and the Phosphorus Color Chart.

Procedure

1.  The test tube was filled to line 6 with Phosphorus Extracting Solution.
2. The 0.5 gram spoon was used to add three measures of soil sample into the test tube.
3. The test tube was capped and mixed gently for one minute.
4. The sample was left to stand for a few moments.
5.  A pipette was used to extract the clear liquid into a second test tube.
6. Six drops of Phosphorus Extract Reactant was added to the solution in the second test tube.
7. The new solution was capped and mixed.
8. One Phosphorus Test Tablet was added to the solution.

9. The solution was capped until the tablet was dissolved. A blue color developed in the test tube.
10. The color of the solution was matched to the Phosphorus Color Chart.

Observations

• Water was clearer in this solution.
• The color changed from purple to blue after the tablet was added. 
• The soil was low in Phosphorus. 

Nitrogen Test

Materials:

• 0.5 gram spoon
• Nitrogen Extracting Solution
• 2 Test Tubes
• Pipettes
• A Timer
• Nitrogen Color Chart
• Caps
• 0.25 gram spoon
• Nitrogen Indicating Powder

Procedure

1. A test tube was filled to the 7 mark with Nitrogen Extracting Solution.

2. A 0.5 g spoon was used to add two soil samples to the solution.

3. The test tube was capped. The solution was mixed for one minute.

4. The cap was removed, and the solution was allowed to settle. 

5. A pipette was used to transfer the clear liquid into a second test tube. 

6. The second test tube was filled to line 3 with liquid. 

7. A 0.25g spoon was used to add two measures of Nitrogen Indicating Powder to the second tube. 

8. The second test tube was capped and mixed gently. The second test tube settled for five minutes, until the solution developed into a pinkish color. 

9. The color of the solution was compared with the Nitrogen Color Chart to determine the amount of Nitrogen in the soil.

Observations

• The color of the Nitrogen solution was the lightest.
• The Nitrogen Indicating Powder made the solution fizz.
• The soil was high in nitrogen.

Potassium Test

Materials

• Potassium Extracting Solution
• 0.5g spoon
• Caps
• Pipettes
• Test tubes
• Potassium Indicator Tablet
• Timer
• Potassium Test Solution

Procedure

1. The test tube was filled to the 7 mark with Potassium Extracting Solution.

2. The 0.5g spoon was used to add four measures of soil to the test tube. 

3. The test tube was capped and mixed vigorously for one minute.

4. The cap was removed, and the solution was let to settle. 

5. A clean pipette was used to transfer the clear liquid into a second test tube to line five. 

6. One Potassium Indicator Tablet was added to the second test tube.

7. The second test tube was capped and mixed until the tablet dissolved.

8. A purplish color appeared inside of the test tube.

9. Two Potassium Test Solution was added added at a time, keeping count. The contents were mixed, and the process of adding and mixing drops was repeated until the solution turned from purple to blue. 

10. The color of the solution was compared to the Potassium level chart, and the level of Potassium was recorded.

Observations

• Soil had a moderate amount of potassium.
• The tablet made the solution turn a purplish color.  

Conclusion

The tests were all useful indicators of the soil's fertility.  The range of the pH was 7.5.  This is a neutral range. Soils with neutral ranges are very fertile, because they are a perfect balance between sour and sweet.  The soil was high in Nitrogen, medium in Potassium, and low in Phosphorous.  The plants in the soil were generally very healthy.