Soil pollution occurs when persistent toxic substances accumulate in soil, harming plant growth and animal health. Soils are essential as they support plant roots and provide nutrients, serve as a habitat for insects and microbes, filter surface water, store carbon to regulate climate, and cycle nutrients. The pH or acidity level of soil must be maintained within a suitable range, typically between 5.5-7, for most plants to thrive, through adding limestone to raise pH or sulfur to lower it. A soil test determines amendments needed to optimize soil conditions for crop yields.

1. SOIL POLLUTION
Paper: CHEMISTRY FOR BIOLOGIST - II
Subject Code: 07AT02
http://www.healthpromotiontrust.org/
By
Dr. G. Balakrishnan
Assistant Professor
Department of Chemistry
Vivekananda College
Madurai, Tamil Nadu

2. Soil Pollution
 Soil pollution is defined as the increase in soils of
persistent toxic compounds, chemicals, salts,
radioactive materials, or disease-causing agents,
which have bad effects on plant growth and
animal health.

3. Importance (Functions) of soils
Soils are essential for life, in the sense
 Medium for plant growth:
(i) Soils support roots and keep them upright for growth.
(ii) Soils provide plants with essential minerals and nutrients
 Habitat for many insects and other organisms:
Insects and microbes (very tiny single-cell organisms) live in the
soils and depend on soils for food and air.
 A Filtration system for surface water:
Filtered water also provides plants with clean, unpolluted water
needed for growth.
 Carbon store and maintenance of atmospheric gases:
(i)Soils help regulate atmospheric Carbon dioxide (CO2) by acting
as a carbon store.
(ii)Nitrogen, phosphorus, and many other nutrients are stored,
transformed, and cycled in the soil.

4. pH of soil
 pH is a measure of hydrogen ion concentration, a measure
of the acidity or alkalinity of a solution.
pH = -log [H+]
 The pH scale ranges from 0 to 14, with pH 7.0 being
neutral. pH less than 7 are acidic, while those with a pH
greater than 7 are basic or alkaline.
 The optimal pH range for most plants is between 5.5
and 7.0; however, many plants have adapted to thrive
at pH values outside this range.

5.  is important to maintain proper levels for plants to reach
their full yield potential.
 Soil pH can be lowered by adding sulfur if it is too alkaline
or increased by adding limestone if it is too acidic.
 Prior to cultivation, a soil test is done and only the
recommended amount of any chemical is added to alter its pH.
 The efficiency of the soil is determined by: timing and
season, placement, and frequency of production.
pH Range
5.0-5.5 5.5-6.5 6.5-7.0
blue berries, sweet
potatoes, irish potatoes
barley , bluegrass, corn,
cotton, peanuts, soybeans,
rice, wheat, water melon
alfalfa, some clovers,
sugar beets