Soil Biological Characteristics SAQ's

Biological Properties of Soil

• Soil acts as a habitat for many organisms, providing benefits such as added nutrients, decomposition of organic matter, and soil structure improvement.
• Soil biomass refers to the total amount of organic matter living in the soil.

Types of Soil Organisms

• Macro-organisms: earthworms, rabbits, and plants
• Micro-organisms: bacteria, fungi, and actinomycetes
• Bacteria: convert organic matter into humus, convert nitrogen into usable forms, and have a symbiotic relationship with plants
• Fungi: responsible for humification, have symbiotic relationships, and enhance water holding capacity, bind soil particles, and help with disease resistance

The Rhizosphere

• The area around a plant root where biological and chemical aspects of the soil are influenced by the root
• High levels of microorganisms are present in this area, feeding on compounds exiting the roots
• A symbiotic relationship exists between the bacteria, fungi, and plants, where both benefit from each other

Earthworms (Lumbricus Terrestris)

• Decompose organic matter to humus and recycle nutrients
• Mix soil layers, improve drainage and aeration, and fertility
• Improve soil structure
• High numbers of worms indicate ideal soil conditions

Conditions Required for Earthworms

• pH 6-8
• Moist soil
• High levels of organic matter
• Warm soil (above 10 degrees)
• Well-aerated soil

Carbon Cycle

• Steps in the carbon cycle: photosynthesis, respiration, consumption, decay, and combustion
• Plants take in CO2 from the atmosphere during photosynthesis and store it as a carbohydrate
• Carbon footprint: the total amount of greenhouse gases produced directly and indirectly by the farmer
• Farmers can reduce their carbon footprint by: planting more trees, reducing diesel usage, growing biofuels, not burning straw, and using eco-tillage and minimum tillage

Carbon Forms

• CO2
• Carbohydrate (CHO)
• Carbonate ion (CO32-)
• Organic carbon: makes up 58% of soil organic matter, stores carbon, and provides energy for the soil microbiome

Nitrogen Cycle

• Nitrogen takes multiple forms: N2, NO3-, NH4, and NO2-
• Processes: nitrogen fixation, decomposition, nitrification, and denitrification
• Nitrogen fixation: conversion of nitrogen gas into nitrate by rhizobium bacteria in clover nodules
• Symbiotic relationship: clover and rhizobium bacteria
• Decomposition: bacteria and fungi decompose dead matter and manure, forming ammonium
• Nitrification: conversion of ammonium to nitrate by Nitrosomas bacteria
• Denitrification: conversion of nitrate back to nitrogen gas by denitrifying bacteria under anaerobic conditions

Biological Properties of Soil

• Soil acts as a habitat for many organisms, including macro-organisms (e.g., plants, rabbits), micro-organisms (e.g., bacteria, fungi), and earthworms.
• Soil organisms add nutrients to the soil through their faeces and decompose organic matter into humus.
• Soil biomass is the total amount of organic matter living in the soil.

Soil Organisms

• Bacteria:
  • Convert organic matter into humus (e.g., actinomycetes)
  • Convert nitrogen into usable forms
  • Have symbiotic relationships with plants (e.g., mycorrhizal fungi)
• Fungi:
  • Responsible for humification of soil organic matter
  • Some have symbiotic relationships with plants
  • Mycorrhizal fungi enhance water holding capacity, bind soil particles together, and help with disease resistance

Earthworms

• Decompose organic matter to humus and recycle nutrients
• Mix soil layers
• Improve drainage and aeration
• Improve fertility
• Improve soil structure
• High numbers of worms indicate ideal soil conditions, which require:
  • pH 6-8
  • Moist soil
  • High levels of organic matter
  • Warm soil
  • Well-aerated soil

Carbon Cycle

• Steps in the carbon cycle:
  • Photosynthesis: plants take in CO2 and store carbon as a carbohydrate
  • Respiration: roots release CO2
  • Consumption: animals eat plant carbohydrates
  • Decay: microorganisms break down organic matter and release CO2
  • Combustion: fossil fuels release CO2
• Carbon footprint: the total amount of greenhouse gases produced by the farmer and their products/services
• Farmers can reduce their carbon footprint by:
  • Planting more trees (afforestation)
  • Reducing diesel usage
  • Growing biofuels
  • Not burning straw
  • Eco-tillage and minimum tillage

Carbon Forms

• CO2
• Carbohydrate: CHO
• Carbonate ion: CO32-

Organic Carbon

• Soil stores a vast amount of carbon, which is made up of 58% organic carbon
• Carbon can provide energy for the soil microbiome
• To calculate Soil Organic Carbon (SOC), multiply the percentage of Soil Organic Matter (SOM) by 58% or 0.58

Nitrogen Cycle

• Nitrogen takes multiple forms:
  • Nitrogen gas (N2)
  • Nitrate (NO3-)
  • Ammonium (NH4)
  • Nitrite (NO2-)
• Processes:
  • Nitrogen fixation: nitrogen is converted into nitrate
  • Decomposition: bacteria/fungi decompose dead matter and manure, forming ammonium
  • Nitrification: ammonium is converted to nitrite and then to nitrate
  • Denitrification: nitrate is converted back to nitrogen gas

Bacteria's Role in Nitrogen Cycle

• Decomposes organic matter to humus
• Converts nitrogen (N2) to nitrate (NO3-)
• Converts ammonium (NH4) to nitrite (NO2-) and then to nitrate (NO3-)
• Converts nitrate (NO3-) to nitrogen gas (N2)

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)

This quiz covers the biological properties of soil, including the benefits of soil organisms, decomposition, and types of soil organisms such as macro-organisms, micro-organisms, and earthworms.