Soil and Water Chemistry

Learn the chemistry of soils and water

Discover applications in agriculture, health and environmental management.

• Learn about chemical reactions in soil.
• Learn about different soil testing methods.
• Develop knowledge about soil classification.
• Learn about ways to improve soil fertility.
• Study the hydrological cycle and its impact on agriculture.
• Apply your new found knowledge with a Problem Based Learning Project.

Lesson Structure

There are 10 lessons in this course:

1. Soil Chemistry: An Introduction
   • Introduction
   • Chemistry Revision (inc. Chemical Terms, Elements, Compounds, Bonds).
   • Soil Redox Reactions.
   • Biogeochemistry and Soil Structure Review.
   • Biogeochemical Cycles.
   • Mineralisation.
   • Immobilisation.
   • Ammonium Fixation.
   • The Urea Cycle.
   • Soil Absorption/Desorption.
2. Soil Chemical Processes
   • Introduction: How Soils Develop.
   • Factors of Soil Formation in More Detail.
   • Weathering Processes of Soil Formation.
   • Soil Profile Description.
   • Soil Classification and Description.
   • Classification of British Soils.
   • Soil Types and Plant Growth.
   • Properties of Soils.
   • Physical and Chemical Properties of Soil.
   • Soil Characteristics and their Relationship to Plant Growth.
3. Soil-Chemical Testing
   • Introduction.
   • Common Soil Tests.
   • Other Soil Cations.
   • The CEC in Soils.
4. Soil Chemistry – Applications in Agriculture
   • The Components of Soil Fertility.
5. Soil Chemistry – Applications in Environmental Management
   • Introduction.
   • Soil Pollutants.
   • Soil Remediation.
6. Water Chemistry - Introduction
   • Water: Chemical and Physical Properties.
   • Hydrological Cycle.
   • Water Resources.
   • Water Footprint.
   • Drought and Impact.
7. Water – Chemistry of Water Sources and Drinking Water
   • Water Sources And Their Chemical Composition.
   • Chemistry of Seawater.
   • Chemistry of Groundwater.
   • Chemistry of Surface Water.
   • Chemistry of Potable Drinking Water.
8. Water – Chemical Testing
   • Introduction.
   • Water PH.
   • Electrical Conductivity.
   • Total Alkalinity.
   • Total Hardness.
9. Water -- Applications in Agriculture and Human Health
10. Water Chemistry -- Applications in Agriculture, Problem-Based Learning Project

Aims

• Describe the dominant geochemical cycles on earth.
• Demonstrate an understanding of basic chemistry including atoms and their components, elements, compounds and chemical reactions.
• Explain the important chemical reactions occurring in soil and their consequences; differentiate between different soil fractions with respect to their nature, size and chemical activity.
• Describe different soil test methods and explain how the test results are used.
• Explore components of soil fertility.
• Describe soil chemistry/fertility factors affecting crop growth in different farming environments. Explain ways of improving soil fertility for crop production.
• Discuss the impact of chemically altering soil vs. cycling and other natural methods.
• Describe inorganic and organic soil pollutants. Discuss effects on health and the environment.
• Discuss ways to remediate soils.
• Outline the components of the earth’s water cycle.
• Describe the main chemical properties of water.
• Explain the various ways in which water is classified.
• Explain the chemistry of different water sources, giving examples of different properties and reactions.
• Describe different water test methods and explain how the test results are used.

HOW THE COURSE WORKS

You can start the course at any time.

It is studied by distance learning, so you can study in the comfort of your own home. But this doesn't mean you are all alone in your studies.  Our highly qualified and friendly tutors are there to help you every step of the way.  If you have any questions at all, they are always happy to help.

Each lesson includes set tasks, and is completed with an assignment which the student submits to their course tutor.  The tutor will mark the assignment and return this to the student with comments and suggestions for further reading.

The following is a short excerpt from the course re Cation Exchange Capacity.

CATION EXCHANGE CAPACITY (CEC) (me (meq)/100 g or cmol(+)/kg)

CEC is an indication of the number of exchange sites within a soil that may temporarily hold positively charged ions. It is generally determined by the amount and type of clay and the amount of organic matter.

You can liken the soil to a magnet – it attracts cations (positively charged ions) and repels anions (negatively charged ions). This knowledge allows people working with soils to understand the nutrients held in a soil and the soil nutrient requirement (in crop growing or pasture management for example). Crop nutrient applications can then be planned an applied according to soil type.

Testing for CEC

CEC and exchangeable cations for saline or alkaline soils are pre-treated for soluble salts and measured using the ammonium chloride pH 7.0 method.

CEC is a general indicator of soil storage capacity for available, positively charged plant nutrients such as Ca, Mg, K and NH4. It can also be determined by measuring residual silver in solution using atomic absorption spectrophotometry or ICP) after 4 hours shaking of the sample in 0.01mol silver-thiourea (AgTU)+.  Displaced (exchangeable) cations are also measured by AAS or ICP. Samples are pre-treated to remove salts by repeated washing in glycol-ethanol.

Silver-thiourea cation exchange and exchangeable cation determinations are rapid in comparison with other methods of measurement. Results are usually comparable. In some instances, the silver-thiourea method appears to overestimate exchangeable magnesium in some saline and alkaline soils and can overestimate exchangeable potassium in some mica-rich soils.

Exchangeable cation status in soils should be assessed not only in terms of the amounts of the particular cations present, but also their relative abundance in comparison with cation exchange capacity as well as other cations. In many instances, when CEC is very low and exchangeable cation concentrations are near to the limit of instrument detection, the relative proportions of cations become meaningless.

Manipulation of CEC and amounts or proportions of cations can involve complex chemistry and site considerations. Cation imbalances can lead to toxicity effects. Seek expert advice since inappropriate chemical manipulations can reduce soil fertility and create further cation imbalances that may be difficult to correct.

Start your professional studies in Soil and Water Chemistry today - suitable for persons working in areas such as:

• Agriculture
• Health Management
• Environmental Management

If you have any questions and want to know more, simply click on "Talk to an Expert" below to connect with one of our specialist tutors - they will be more than happy to help you with any queries you may have.