– The soil pH is a measure of its acidity. When the pH is in the right range, plants can easily take up the nutrients they need from the soil.
– Soil Conductivity is a measure of salt content (salinity) of the soil and thus an important indicator of soil health.
– After collecting the soil from the field, aggregates are removed, larger pieces of plant material picked up manually and it is sieved properly by using 2 mm sieve.
– In order to measure pH and conductivity soil samples have to be extracted first. The extraction ratio is 1:5.
– MilliQ/deionized water and 0.01 M CaCl2 are used as an extraction media. The reason for using CaCl2 solution is that the Ions in the CaCl2 solution prevent excess extraction of Ions from clay minerals therefore, the results in CaCl2 solution are more reproducible and better represent the conditions in soil environment than those measured in water.
– 5g of air dried soil sample (6g if the soil is field fresh) is weighed into 50ml labelled centrifuge tubes. 3 replicates are used.
– 0.01M CaCl2 solution is prepared in the usual way. In order to prepare 1L of 0.01M CaCl2 solution we have to weigh 1.11g of CaCl2.
– 25 ml of 0.01 M CaCl2 for Sample 1 (3 Replicates) and 25 ml of MilliQ water for Sample 2 (3 Replicates) are added with a dispenser.
– The samples are shaken for 1 h on the bench shaker at 120rpm and left for another 1 hour for equilibration.
– We need to calibrate our pH meter with 3 buffer solutions (pH 4, pH 7 and pH 10).
– After calibration the pH electrode is dipped into the extracted solution but not the soil. Care should be taken so that the electrode does not touch the bottom of the beaker containing the solution.
– Reading is taken after approx. 30 – 60s or after the pH readings have stabilized. We have to clean the electrode after each measurement with distilled water and dry softly with a tissue.
– Note the pH value to 2 decimal places. Consider temperature dependency (measure temperature).
– After finishing pH measurement the electrode is rinsed with distilled water and dried with a soft tissue and dipped into a solution.
– In order to measure electrical conductivity we have to change the mode of the pH meter. EC electrodes need to be cleaned with distilled water and wiped with soft tissue. Now every procedure is the same as pH measurement.