he most important factor affecting the availability of these nutrients is soil pH, a measure of the amount of hydronium ion (H+) that is present in solution. Pure water has a neutral pH of 7, lower values mean that the solution is acidic and soils with pH higher than 7 are alkaline. Different crops vary in their response to acid and alkaline soil conditions (Mathers, 2001). However, for most field crops, slightly acidic (pH = 5.6) to neutral soils are optimal for growth. Soil pH affects plant growth and productivity indirectly because, depending on the nutrient, availability is affected which can result in nutrient deficiency or nutrient toxicity. In higher pH or alkaline soils, result in deficiencies in the essential micronutrients iron, zinc, and manganese. Soil pH of less than 5.5 is already considered strongly acidic and will not support growth of economically important crops. Thus, the right soil pH is a requirement for maximum yield production.
The development of acid soils has been due to high weathering brought about by warm temperatures and rainfall, and manmade events like the continuous use of nitrogen fertilizers and acid rain effects. At pH below 6 or under acidic soils, increased availability of micronutrients like iron, manganese, zinc , copper and aluminium result in toxicity symptoms (CSIRO Plant Industry, 2004); while decreased availability of phosphorus results in deficiency of this element . This is very true in humid countries where soil acidity is often associated with low crop productivity (Schroth, Lehman, & Barrios, 2003).
The class was divided into eight groups. Each group was asked to bring soil samples from the area near their residence. In the laboratory, the pH and temperature of pure water was determined. After adding water to the soil and mixing the slurry, the pH and temperature of each sample were measured. Mean values of the soil pH of each group were determined, and the hydronium ion concentration was calculated using the