Objective: The goal of this experiment is to test the accuracy of the NPK sensor when used with soil that has been amended with a 14-14-14 fertilizer.
Materials:
- NPK Sensor
- Five packets of 0.1g of 14-14-14 Fertilizer
- Distilled Water
- 5kg Soil with predetermined NPK values (Control Soil)
Procedure:
- Control Measurement:
- Insert the NPK sensor into the control soil (5kg with predetermined NPK values).
- Set a timer for 30 minutes.
- After 30 minutes, note the NPK reading on the sensor. This is your control/baseline reading. Record this value.
- Prepare Soil Samples:
- Divide the 1kg of soil into five equal portions, each weighing 1kg. Use a scale for accuracy. Place each portion in separate containers.
- Measure Soil Samples After Division:
- For each portion of the soil, follow these steps:
- Insert the NPK sensor into the soil in the container.
- Set a timer for 30 minutes.
- After 30 minutes, note the NPK reading shown on the sensor. This is your pre-fertilization reading for each divided sample. Write down these values.
- For each portion of the soil, follow these steps:
- Apply Fertilizer:
- Sprinkle 0.1g of 14-14-14 fertilizer evenly on the surface of the soil in each container.
- Mix the soil and fertilizer until they are well combined using a clean stirrer. This ensures a uniform mixture of soil and fertilizer in each container.
- Hydrate Soil:
- Measure an equal volume of distilled water for each soil sample (the volume depends on the soil’s capacity to absorb water without becoming too soggy).
- Pour the measured water into each container, making sure that each portion of soil receives an equal amount of water.
- Mix the soil again until the water is evenly distributed in each container.
- Measure Fertilized Soil:
- Let the soil samples rest for 24 hours. This will allow the fertilizer to react with the soil.
- After 24 hours, repeat the measurement process for each soil sample:
- Insert the NPK sensor into the soil in the container.
- Set a timer for 30 minutes.
- After 30 minutes, note the NPK reading shown on the sensor. This is your post-fertilization reading. Write these values down.
Data Analysis:
- Compare Readings:
- Compare the control/baseline NPK readings (from Step 1), the pre-fertilization readings of divided samples (from Step 3), and post-fertilization readings (from Step 6). The post-fertilization readings should be higher than both the control and pre-fertilization readings because 14-14-14 fertilizer was added to each sample.
- Calculate Accuracy:
- The accuracy of the NPK sensor can be evaluated by comparing the final post-fertilization readings with the expected increase due to the added 14-14-14 fertilizer. If the NPK sensor readings accurately reflect this expected change, it means the sensor is working correctly.
