2.7. Extraction of Micro-nutrients from soil

Extraction of pH -
Weigh 10 g of dried soil in centrifuge tube. Add 25 ml of Distilled water to it. Shake the solution for 5 min and allow it to settle down the soil for 10-15 min. Filter out the supernatant using syringe filter and 0.45 micron filter membrane. Test the filtrate for determination of pH using pH strips and the Akvo Caddisfly software as mentioned below.
Extraction of NPK -
Weigh 5 g of dried soil in centrifuge tube. Add 25 ml of Mehlich 1 solution to it. Shake the solution for 5 min and allow it to settle down the soil for 15 min. Filter out the supernatant using syringe filter and 0.45 micron filter membrane. Test the filtrate for determination of NPK using NPK strips and the Akvo Caddisfly software as mentioned below.

2.8. Quantification of NPK & pH using smartphone app -

Testing of pH -
Take filtrate sample in a small container. Take smartphone with Akvo caddisfly application in it. Click on Akvo Caddisfly app and there is option of Strip test will appear on the screen. Select the pH. Use color card developed by Akvo for calibration. Focus the camera on the  color card and press the button for "Prepare for test" and camera will check shadow and brightness as the control parameters. After quality check it will show the message "Success".
Take out pH strip from the box and process it according to the instructions given on the screen and place onto the black surface of color card and click on "Start". Focus the camera on color card and app will read colour on strip and compare it with existing calibrated  colors and it will give value of pH.  Take used strip and put in a empty box provided with kit.
Testing of NPK - 
Take filtrate sample in a small container. Take smartphone with Akvo caddisfly application in it. Click on Akvo Caddisfly app and there is option of Strip test will appear on the screen. Select the corresponding parameter to test. Use color card developed by Akvo for calibration. Focus the camera on the  color card and press the button for "Prepare for test" and camera will check shadow and brightness as the control parameters. After quality check it will show the message "Success".
Take out strip from the box and process it according to the instructions given on the screen and place onto the black surface of color card and click on "Start". Focus the camera on color card and app will read colour on strip and compare it with existing calibrated  colors and it will give value of corresponding parameter as suggested below figure 3. Take used strip and put in a empty box provided with kit. The strips used are Nitrate-N and Nitrite (N) combined strip from Hach (Product:2745425), Phosphate from Quantofix (Ref:91320) and Potassium from Merck (Cat. No.:117985).