EXPERIMENT ON DETERMINATION OF THE pH OF A SOIL SAMPLE

Determination of the pH Value of soil sample

To determine the pH of a soil sample so as to know the kind of plants that will thrive in the soil where the sample was obtained.

THEORY

The term pH refers to the measurement of the concentration of hydrogen ions in a single solution and is defined as the negative test of the concentration of H + ions in water and water. The values of pH 0 to just under 7 are called acids and pH values slightly higher than 7 to 14 are called placides. When the H + and OH-ions bond is the same, it is called neutral pH. The pH is mathematically represented as log 1 / H = - log H + U are only acidic or basic. The global pH, called the nickname of the world, can be expressed using the pH scale. Solids with pH above 7 are basic or sweet. And solids with pH less than 7 are acids or acids. A land with a pH of 7 is not acidic or basal; It is neutral. The pH of the sole is an important factor in determining which plants grow because they contain nutrients at their disposal. There are three main nutrients available: nitrogen, phosphorus and potassium for a healthy plant development. Because the conditions are quite large, they are called macronutrients. They are the main ingredient in most fertilizers that farmers and gardens add to their place. The vegetables also had other nutrients, like manganese or manganese, but only in limited quantities. These nutrients are called micronutrients. The availability of these nutrients should not be greater than the quantity but also in the present way, at the speed with which they are released from the soil and at the pH of the site. In general, macronutrients are more available only with pH and the micronutrients are more available only with a low pH.

METHODOLOGY

This method is essentially based on the measurement of potential, developed across an indicator or the glass electrode on account of the difference activity of H+ ions in and out of the electrode, i.e., in the bathing solution. The potential difference between the glass electrode and calomel electrode is expressed in pH units.

APPARATUS REQUIRED

1.     50mL beaker, 100 mL graduated cylinder
2.     Electric PH meter
3.     Tissue paper
4.     Soil sample (at least 40 grams)
5.     Buffers (at least two)
6.     Timer or stopwatch
7.     Glass rod
8.     Triple beam balance
9.     Spatula
                           

CHEMICALS REQUIRED

1.     Potassium Chloride (KCl)
2.     Distilled water
3.     Buffers solution of pH 4.0 and 7.0

PROCEDURE

1.     I weighed 20g of air-dried soil into a beaker of weight 33.2g using the triple beam balance.
2.     I added 20ml of distilled water and allowed it to stand for 10minutes while stirring occasionally with a glass rod.
3.     The electrodes of the standardised PH meter was inserted into the partly settled suspension and the PH was measured.

OBSERVATION

1.     The soil mixture settled into 2 layers; a top water layer and a bottom soil layer.
2.     When the glass sensor was placed in the dilute potassium chloride solution (KCL), the pH value on the pH meter gave a reading of 7.0 which is neutral.
3.     When the distilled water was poured into the soil sample, it was observed that air voids trapped in the soil escape and the soil sample became saturated.
4.     The mixture of water and soil was not homogenous i.e. the soil was partly settled in the water.
5.     There was a brief fluctuation in the reading of the pH meter

Sample	pH obtained
1.	8.0

<5.0	5.5	6.0	6.5-7.5	7.5-8.5	>8.5
Strongly acidic	Moderately acidic	Acidic	Neutral	Moderately    Alkaline	Strongly Alkaline
			Most plants thrive well here

In conclusion, the pH obtained for the soil sample is 8, hence it is moderately alkaline. A soil with pH of 8.0 has a high abundance of Magnesium (Mg), Calcium (Ca), Sulphur (S), Potassium (K), Molybdenum and Nitrogen (N). It contains in small quantity Iron (Fe), Manganese (Mn), Copper (Cu) and Zinc (Zn) 

PRECAUTIONS

1.     I ensured the pH meter and sensor works well by placing the pH sensor into buffers of known pH value.

2.     I ensured the pH sensor was rinsed with distilled water and wiped with tissue paper before and after using it to measure the pH of the slurry sample.

3.     I ensured that before using the pH meter, I allowed the electrode to stand in dilute KCL solution for at least 2 hours so as to obtain the best results.

4.     I ensured that the electrode used in the pH meter was handled carefully as it is very fragile.

CONCLUSION

Hence, the plants that can thrive in a soil of pH 8.0 are;

1.     Asparagus (6.0-8.0)

2.     Leek (6.0-8.0)

3.     Marjoram (6.0-8.0)

RECOMMENDATION

The soil contains high alkaline with pH level of 8 and most plants may find it hard to thrive in this soil type hence, lowering the soil’s alkalinity level should be done with the help of Ammonium Sulphate and organic materials. This will help to lower the pH of the soil, thus allowing for more plants to be able to thrive well.