Podcast
Questions and Answers
What is the primary function of earthworms in soil?
What is the primary function of earthworms in soil?
Decompose organic matter to humus and recycle nutrients
What is the term for the total amount of organic matter living in the soil?
What is the term for the total amount of organic matter living in the soil?
Soil Biomass
What is the role of mycorrhizal fungi in soil?
What is the role of mycorrhizal fungi in soil?
Enhance water holding capacity, bind soil particles together, and help with disease resistance
What is the process of converting organic matter into humus?
What is the process of converting organic matter into humus?
Signup and view all the answers
What is the term for the area around a plant root where the biological and chemical aspects of the soil are influenced by the root?
What is the term for the area around a plant root where the biological and chemical aspects of the soil are influenced by the root?
Signup and view all the answers
What is the benefit of adding organic matter to soil?
What is the benefit of adding organic matter to soil?
Signup and view all the answers
What is the definition of a symbiotic relationship?
What is the definition of a symbiotic relationship?
Signup and view all the answers
What is the purpose of adding lime to soil?
What is the purpose of adding lime to soil?
Signup and view all the answers
What is the ideal temperature for soil to be considered warm, and how does it affect the growth of plants?
What is the ideal temperature for soil to be considered warm, and how does it affect the growth of plants?
Signup and view all the answers
What is the purpose of cultivating soil, and how does it relate to the carbon cycle?
What is the purpose of cultivating soil, and how does it relate to the carbon cycle?
Signup and view all the answers
How do farmers reduce their carbon footprint, and what is the significance of afforestation in this process?
How do farmers reduce their carbon footprint, and what is the significance of afforestation in this process?
Signup and view all the answers
What is the relationship between Soil Organic Matter (SOM) and Soil Organic Carbon (SOC), and how is SOC calculated?
What is the relationship between Soil Organic Matter (SOM) and Soil Organic Carbon (SOC), and how is SOC calculated?
Signup and view all the answers
What are the different forms of nitrogen in the nitrogen cycle, and how do they relate to each other?
What are the different forms of nitrogen in the nitrogen cycle, and how do they relate to each other?
Signup and view all the answers
What is the role of bacteria in the nitrogen cycle, and how do they contribute to nitrogen fixation, nitrification, and denitrification?
What is the role of bacteria in the nitrogen cycle, and how do they contribute to nitrogen fixation, nitrification, and denitrification?
Signup and view all the answers
What is the main effect of adding organic matter to a soil with low CEC?
What is the main effect of adding organic matter to a soil with low CEC?
Signup and view all the answers
Which cation is not commonly found in soils?
Which cation is not commonly found in soils?
Signup and view all the answers
What is the optimum pH range for most plant growth?
What is the optimum pH range for most plant growth?
Signup and view all the answers
What is the role of lime in soil?
What is the role of lime in soil?
Signup and view all the answers
What is the primary reason why cations are attracted to soil particles?
What is the primary reason why cations are attracted to soil particles?
Signup and view all the answers
What type of ions determine the acidity of the soil?
What type of ions determine the acidity of the soil?
Signup and view all the answers
What is the result of the adsorption of cations onto the surface of soil particles?
What is the result of the adsorption of cations onto the surface of soil particles?
Signup and view all the answers
What is the effect of liming on soil?
What is the effect of liming on soil?
Signup and view all the answers
What is the typical CEC of sandy soils?
What is the typical CEC of sandy soils?
Signup and view all the answers
Why does humus have a higher Cation Exchange Capacity (CEC) than clay?
Why does humus have a higher Cation Exchange Capacity (CEC) than clay?
Signup and view all the answers
What is the benefit of high humus content in soil in terms of flocculation?
What is the benefit of high humus content in soil in terms of flocculation?
Signup and view all the answers
What is the effect of pH on CEC?
What is the effect of pH on CEC?
Signup and view all the answers
What is the role of cations in cation exchange?
What is the role of cations in cation exchange?
Signup and view all the answers
What is the significance of the Cation Exchange Capacity (CEC) of soil?
What is the significance of the Cation Exchange Capacity (CEC) of soil?
Signup and view all the answers
Why can a cation with a +2 charge (Ca2+) replace two separate cations each with +1 charge (H+)?
Why can a cation with a +2 charge (Ca2+) replace two separate cations each with +1 charge (H+)?
Signup and view all the answers
Study Notes
Biological Characteristics of Soil
- Soil organisms add nutrients in the form of faeces
- Soil organisms decompose organic matter to humus (humification)
- Soil organisms add organic matter when they die
Soil Biomass
- Soil biomass is the total amount of organic matter living in the soil
Types of Soil Organisms
- Macro-organisms: earthworms, plants, rabbits
- Micro-organisms: bacteria, fungi
- Bacteria:
- Convert organic matter into humus
- Convert nitrogen into usable forms
- Fungi:
- Responsible for humification of soil organic matter
- Some have a symbiotic relationship with other organisms
Definitions
- Carbon Footprint: the total amount of greenhouse gases produced directly and indirectly by a farmer
- Symbiotic Relationship: a relationship where two or more organisms live in close contact, where at least one benefits, and neither are harmed
- Mutualistic Relationship: a relationship where both organisms benefit
- Parasite: an organism that lives on or in a living host, usually causing harm
- Saprophyte: an organism that feeds off dead organic matter
- Rhizosphere: the area around a plant root where the biological and chemical aspects of the soil are influenced by the root
Earthworms
- Decompose organic matter to humus and recycle nutrients
- Mix soil layers
- Improve drainage and aeration
- Improve fertility
- Improve soil structure
Conditions Required for Soil Organisms
- pH 6-8: add lime to raise pH
- Moist soil: not too dry or waterlogged
- High levels of organic matter: spread FYM or other organic manures
- Warm soil: not too cold (above 10 degrees)
- Well-aerated soil: cultivate soil
Carbon Cycle
- Steps in the carbon cycle:
- Photosynthesis
- Respiration
- Consumption
- Decay
- Combustion
- Farmers reduce their carbon footprint by:
- Planting more trees (afforestation)
- Reducing diesel usage
- Growing biofuels
- Not burning straw
- Minimum tillage
Organic Carbon
- To calculate Soil Organic Carbon (SOC), multiply the percentage of Soil Organic Matter (SOM) by 0.58
Nitrogen Cycle
- Nitrogen takes multiple forms: nitrogen gas (N2), nitrate (NO3-), ammonium (NH4), nitrite (NO2-)
- Processes:
- Nitrogen fixation
- Decomposition
- Nitrification
- Denitrification
- Bacteria role in the nitrogen cycle:
- Decomposes OM to humus for energy and recycles nutrients
- Converts nitrogen (N2) to nitrate (NO3-) (nitrogen fixation)
- Converts ammonium (NH4) to nitrite (NO2-) then to nitrate (NO3-) (nitrification)
- Converts nitrate (NO3-) to nitrogen gas (N2)
Flocculation
- Flocculation is the clustering of soil particles to form larger structures called floccules, which improves soil structure.
- Cations such as Ca2+ and Mg2+ promote flocculation by being attracted to the negative charges on soil particles.
- Soil particles have a negative charge, with smaller particles having more negative charges.
- Cations are adsorbed to the surface of soil particles, and polarized water holds soil particles together, trapping larger sand and silt in a floccule structure.
- High humus content is more beneficial than high clay content because humus is more fertile, holds more water, has a higher Cation Exchange Capacity, encourages more earthworm activity, and has more negative charges, resulting in an increased rate of flocculation.
Cation Exchange
- Cation exchange is the ability of the soil to adsorb cations onto its surface and exchange them for other cations.
- Cations are attracted to the negative charge of clay/humus particles and are adsorbed on the surface.
- Cations can be released into soil water (soil solution) and be replaced by others, supplying minerals to plants.
- A cation with a +2 charge (Ca2+) can replace two separate cations each with +1 charge (H+).
- Cations are removed from soil solution by plant roots.
- Colloidal humus particles have three times higher cation exchange capacity than colloidal clay particles.
- Adding organic matter to a soil with poor CEC (like sand) will increase its CEC.
- Main cations involved in cation exchange are Ca2+, Mg2+, Al3+, H+, and K+.
- Note that nitrate (NO3-) cannot be held, and sandy soils have the lowest CEC.
Soil pH
- Soil pH is the acid-base scale, measuring the concentration of H+ ions in a solution.
- Acidic soils have a pH of 0-6, neutral soils have a pH of 7, and basic soils have a pH of 8-14.
- The concentration of acidic ions adsorbed onto the surface of the soil determines the acidity of the soil.
- Acidic ions include H+ and Al3+, while alkaline/basic ions include Ca2+ and Mg2+.
- Importance of Soil pH:
- Lime increases Ca cations available for exchange (H, K, Al).
- As pH increases, the amount of negative charges on soil colloids increases, leading to greater CEC.
- Liming reduces ‘acid leaching’.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
This quiz covers the biological characteristics of soil, including the benefits of soil organisms, soil biomass, and types of soil organisms such as macro-organisms and micro-organisms.
