The document outlines the work schedule and learning units for a soil profiles unit over 4 weeks. Week 1 covers the properties of soil like colour, texture, pH and structure through lessons. Week 2 focuses on soil profiles and the different soil horizons. Week 3 covers soil carbon stabilization and includes a lesson, practical work and a test. The techniques to apply soil carbon stabilization like crop rotation and cover cropping are also summarized.

1. WORK SCHEDULE FOR UNIT 6 (SOIL PROFILES)
WEEK (DATE) LEARNING UNIT TOPIC (SUB-TOPIC) TEACHING
METHOD
Week 1&2
 (08 September
2023)
 (15 September
2023)
6
6
SOIL PROFILES
- Soil contains a
living, complex
ecosystem.
- Properties of
soil are colour,
texture, pH, and
structure
Lesson
Lesson
Week 3&4
 (22 September
2023)
 (29 September
2023)
 (06 Oct 2023)
6
6
6
SOIL CARBON
STABILIZATION
- Soil is reliant on
the stabilization
of carbon for
fertility
purposes.
- Practical 1
- Class test 1
Lesson
Practical work
Test
SOIL PROFILE FOR UNIT 6

2. INTRODUCTION:
Soil is the collection of natural bodies on earth’s surface containing living matter and
supporting, or capable of supporting plants. Its upper limit is the atmosphere (air) or water,
and at its lateral margins it grades to deep water or barren areas of rock and ice. Its lower
limit is normally considered to be the lower limit of the common rooting zone (root zone)
of the native perennial plants, a boundary that is shallow in the deserts and tundra and
deep in the humid tropics.
1. SOIL DEFINITION
• It is a renewable resource that forms part of the natural environment and is important for
most existence of
life on earth.
• The soil
provides most of
the nutrients
needed for plant
growth and also
helps purify
water.
• It is a mixture
of rocks, air,
minerals,
decaying organic
matter, water and
tons of
mircoorganisms
e.g. bacteria

3. 2. PHYSICAL PROPERTIES OF SOIL
A. SOIL COLOUR
• This is the most visible and obvious trait of soils.
• Soil colours range from shade of black and brown to white and grey.
• The darker the soil, the more fertile it is, and the more nutrients it contain,
• whereas, the lighter the soil, the less fertile it is and the less nutrients it contains.

4. B. SOIL TEXTURE
• Soil particles are classified by size; from largest to smallest they are called sand, silt, and
clay.
• Soil texture is dependent on the size of particles found in it.
• It further determines the porosity of the soil, its water holding capacity and the type of
plants that grow in it.
• There are three main soil textures: sand, silt and clay.
• Sandy soil is not sticky, it feels gritty and does not have much nutrients.
• Silt soil is smaller than sandy soil and it feels powdery like flour.
• And, Clay soil is very sticky when wet and very dry and powdery
C. SOIL PH INDEX

5. • The acidity or alkalinity of the soil indicates the degree of leaching.
• Different plants require a different pH for best growth but a value between 5 and 7 is
suitable for most plants.
• The pH also influences the soil porosity, soil colour, soil texture and the type of plants that
can be grown on the soil.
D. SOIL STRUCTURE
• Soil structure refers to how soil grains are bound together to form a larger unit.
• The soil can be granular (biscuit crumbs) or columnar with some vertical columns or
blocks.
• Soil structure also gives off the health of the soil, as to whether it is good, moderate or
poor condition.

6. SOIL PROFILES
• Soil profiles are made up of a series of soil layers each called a horizon.
• These extend from the surface to the parent rock material
• Four types of horizons
* The O horizon
* The A horizon
* The B horizon
* The C horizon
The O and A horizons

7. • The O horizon is regarded as the humus, because it contains Organic material such as
leaves, pine, twigs and decaying animal tissues
• The A horizon is the topsoil and is the most fertile part of the soil. It is dark in colour.
The B and C horizons
• The B horizon, also called subsoil is the less fertile part of the soil because it is far from
the organic matter,
• And the C horizon is where the partially weathered parent rock material is found and is
responsible for providing soil with minerals
ELEMENTS FOUND IN SOIL

8. SOIL CARBON STABILIZATION
• In a soil ecosystem and even in an individual soil horizon, several mechanisms of SOC
stabilization may function simultaneously to different degrees
• Soil Carbon Stabilization. Soil OC stabilization can be termed as any action which slows
down the decomposition of SOM by reducing the mineralization rate
How would you apply soil carbon stabilization

9. Application : Stabilization is accomplished by increasing the shear strength and the overall bearing
capacity of a soil.
Technique: Traditional soil carbon stabilization techniques use sodium silicate, cement, and other
chemical pulp as grout.
Result: the presence of carbon in soil decreases its permeabilitity whilst increasing its fertility
and bearing capacity
Crop Rotation:
Implement diverse crop rotations that include a mix of plants with different root structures and
growth habits. This can increase the diversity and quantity of organic matter input into the soil.
Cover Cropping:
Plant cover crops during periods when the main cash crop is not actively growing. Cover crops
protect the soil from erosion, add organic matter, and promote microbial activity.
No-Till or Reduced Tillage:
Minimize or eliminate tillage practices, as tillage can disrupt soil structure and accelerate the
decomposition of organic matter. No-till or reduced tillage systems help to preserve soil
aggregates.
Here's a detailed explanation of the soil carbon sequestration process:

10. Flow diagrams above
Photosynthesis:
The process begins with plants, which absorb carbon dioxide from the atmosphere through tiny
pores called stomata in their leaves.Using energy from sunlight, plants convert this CO2, along
with water, into glucose (a type of sugar) and oxygen through a process called photosynthesis.
Carbon Allocation:
Some of the glucose produced during photosynthesis is used by the plant for energy, growth, and
reproduction.However, a significant portion of it is transported down through the plant's roots into
the soil. This is known as carbon allocation.
Rhizodeposition:
When the glucose and other organic compounds reach the roots, they are released into the soil
through a process called rhizodeposition.These exudates (organic compounds released by roots)
provide a food source for soil microbes.
Microbial Activity:
Soil microbes, including bacteria, fungi, and other microorganisms, consume the organic
compounds released by plant roots.As they feed on these compounds, they respire, releasing some
CO2 back into the atmosphere. However, a significant portion of the carbon is transformed into
stable organic matter.

11. Stabilization of Organic Matter:
Some of the organic matter that microbes consume is transformed into stable forms of carbon that
can persist in the soil for extended periods.This stable organic matter is less likely to be
decomposed and released back into the atmosphere.
Physical Protection:
Some of the stable organic matter becomes physically protected within soil aggregates. Aggregates
are clumps or clusters of soil particles bound together by organic matter and minerals.This physical
protection makes it harder for decomposers to access and break down the organic matter.
CONCLUSION:
Soil organic carbon (SOC) constitutes a crucial element within the soil matrix, exerting
profound influence on the functionality of terrestrial ecosystems. The accumulation of
SOC arises from intricate interplays among dynamic ecological processes, namely
photosynthesis, decomposition, and soil respiration. Over the last century and a half,
human endeavors have engendered shifts in these processes, resulting in the depletion
of SOC and an aggravation of global climate change. Nevertheless, these human-induced
transformations also present an opportunity for the reintegration of carbon into the soil,
offering a potential avenue for climate mitigation.
As we look ahead, the prospect of heightened temperatures and elevated levels of
atmospheric CO2, coupled with historical land use practices and evolving land
management techniques, will likely yield intricate and multifaceted patterns of SOC
capacity within diverse soil profiles. This underscores the intricate nature of the soil-
carbon relationship, necessitating a nuanced approach in our efforts to bolster carbon
sequestration.
Recognizing and leveraging these dynamics holds significant promise in our collective
endeavor to combat climate change and fortify the resilience of terrestrial ecosystems.

12. In essence, the intricate interplay of ecological processes, influenced by both natural and
anthropogenic factors, underscores the pivotal role of SOC in the broader context of
environmental sustainability. Understanding these dynamics empowers us to make
informed decisions and implement strategies that enhance soil health, mitigate climate
change, and fortify the ecological integrity of our planet.

13. REFERENCE LIST:
• Amritha, K. T. K. (2016). ‘Soil profile, soil erosion, soil conservation, control on floods’.
[PowerPoint presentation]. Available at: https://www.slideshare.net/AmrithaKTK/soil-
profile-soil-erosion-soil-conservation-control-on-floods-69527117?qid=a7b04e95-be5f-
4eea-8f79-2a3e4df376a5&v=&b=&from_search=2. Accessed: 13 August 2023.
• Ersek, K. (2018). ‘10 inspirational quotes on soil’. [PowerPoint presentation]. Available
at: https://www.slideshare.net/KaitlynErsek/10-inspirational-quotes-on-soil. Accessed: 20
August 2023.
• Farooqi, S., Rahman, A. & Cihani, J. (2015). ‘Soil profile’. [PowerPoint presentation].
Available at: https://www.slideshare.net/Saadfarooqi/soil-profile-
54182486?next_slideshow=1. Accessed: 17 August 2023.
• Fant M. O. (2019). ‘Introduction to soil: physical properties (part 1)’. [PowerPoint
presentation]. Available at: https://santacruzpermaculture.com/2019/06/soil-physical-
properties/. Accessed: 23 August 2023
• Gautam, P. (2017). ‘Physical properties of soil’. [PowerPoint presentation]. Available at:
https://www.slideshare.net/GautamParghi/physical-properties-of-soil-74587908.
Accessed: 16 August 2023.
• Hirst, M (1999). Weathered olivine basalt. [Image]. Available from:
https://geodil.dperkins.org/h/2458.html. Accessed 21 August 2023.
• Ehrenfeld, J. G., Kaldor, E. & Parmelee, R. W. Vertical distribution of roots along a soil
toposequence in the New Jersey pinelands. Canadian Journal of Forest
Research 22, 1929-1936 (1992).
• Houghton, R. A. Balancing the global carbon budget. Annual Review of Earth and
Planetary Sciences 35, 313-347 (2007).
• Hungate, B. A., et al. The fate of carbon in grasslands under carbon dioxide
enrichment. Nature 388, 576-579 (1997).

14. • Johnson, N. (2014). The secret to richer, carbon-capturing soil? Treat your microbes well.
Available at: https://grist.org/food/the-secret-to-richer-carbon-capturing-soil-treat-your-
microbes-well/. Accessed: 23 August 2023.
• Kretch, M. J. (2005). ‘Soil horizons’. [PowerPoint presentation]. Available from:
https://www.slideshare.net/Teach5ch/soil-horizons?qid=9ffe3b1a-0b18-47a9-b1e6-
8005cfff31d5&v=&b=&from_search=1 . Accessed: 24 August 2023.
• Karsten, H., Vanek S. & Zimmerer, (n.d). Top: pie chart showing the typical physical
composition of most soils used in food production. [Image]. Available at:
https://www.eeducation.psu.edu/geog3/node/1029 . Accessed: 20 August 2023
• Marchuk, S. (2009). Relationships between soil properties and spatial geophysical and
terrain data in the Angas-Bremer Plains. Geology, 1(5). doi: 10.13140/RG.2.1.1362.920
• NZ Soils. (n.d). Soil formation-topography. [Image]. Available
at:http://www.nzsoils.org.nz/Topic-Basics_Of_Soils/Topography/. Accessed: 24 August
2023.
• O’Sullivan L., McConnell B., Scanlon R., Walsh S. & Creamer R. (2018). Soil formation.
World Soils Book Series, 2(1): 11-36. doi: 10.1007/978-3-319-71189-8-2.
• Sri, K. (2015). ‘Soil pollution’.[PowerPoint presentation]. Available at:
https://www.slideshare.net/kavyasri12/soil-pollution-ppt. Accessed: 17 August 2023.
• Whitehouse, M. (2011). ‘Properties of soil (teach)’. [PowerPoint presentation]. Available
at: https://www.slideshare.net/MMoiraWhitehouse/properties-of-soils-teach-9807299.
Accessed: 17 August 2023.
• Via Afrika. (2012). Geography, Grade 11. Cape Town: Via Afrika Publishers.