Soils 3 Flashcards
(12 cards)
Identify the three main drivers that result in a healthy soil biota
- Organic matter from plant residues
- the fuel for biota
- more fuel = more biological activity
- Cultivation
- Results in a lot of microbial activity in the short term resulting in a reduction in organic matter, ultimately lowering biological activity
- Soil pH
- as soils become more acidic, microbial activity slows down and earthworms disappear
- aim for pH$5.5+
Understand the various roles that soil biota play in keeping a balanced healthy soil
- Turnover organic matter
- Transfer nutrients
- Disease transmission and prevention
- Pollutant degradation
Understand the major species of the food web in soils
Fungi
- Plant-like cells that grow in threadlike structures or hyphae that make a mass called mycelium
- Three functional groups
- Decomposers
- Mutualists
- Pathogens
- All three groups help aggregate the soil
Understand the major species of the food web in soils
Fungi - Decomposers
convert dead organic matter into fungal biomass, CO2 and organic acids, they are capable of degrading cellulose, proteins and lignin, and convert them to material that is more accessible to other organisms
Understand the major species of the food web in soils
Fungi - Mutualists
colonise plant roots and help the plant obtain nutrients such as phosphorous, as well as hide roots from pests and pathogens
Understand the major species of the food web in soils
Fungi - Pathogens
penetrate the plant and decompose living tissue, resulting in weakening or killing the plant
Understand the major species of the food web in soils
Bacteria
- Decomposers
- decompose organic matter, especially in the early stages when moisture levels are high
- Sulphur oxidisers
- convert sulphides (cannot be taken up by plants) into suphates (can be taken up by plants)
- Aerobes and anaerobes
- Actinobacteria
- slowly break down humates in soils (prefer pH 5+)
- Nitrogen fixers
- rhizobium live in root nodules on legumes and extract nitrogen gas from the air to convert it to plant useable nitrogen
- Disease suppressors
Understand the major species of the food web in soils
Nematodes
- Small, non-segmented worms around 50um and less than 1mm long
- Live mainly in soil an feed on fungi, bacteria, soil organisms, and sometimes plant roots
- Work to cycle nutrients (the ammonium stored in the nodes of bacteria and fungi), disperse microbes (bacteria and fungi cannot move around the soil help, and control diseases and pests (attack and kill a range of pests such as borers, grubs, thrips and beetles)
Understand the major species of the food web in soils
major species
- Fungi
- Bacteria
- Nematodes
- Mites
- Earthworms
- Larvae, termites, ants & beetles
Understand the major species of the food web in soils
Mites
- Prey on soil organisms
- mostly on decomposing plant material or fungi
- Can be successfully used as biological control agents
- Shred material into small pieces
- increasing surface area available to bacteria and fungi
Understand the major species of the food web in soils
Earthworms
- Improves nutrient availability
- feed on plant debris and make these materials more available to plants
- Improve drainage
- extensively burrow causing loosening and aeration of the soil (water infiltration improves up to 10x)
- Improve soil structure
Understand the major species of the food web in soils
Larvae, termites, ants & beetles
- Macrofauna that spend at least part of their life cycle underground
- Termites and ants are particularly important in soil turnover and carrying materials deeper into the soil profile
- Termites and ants more important than earthworms in semi-arid climates
- Dung beetles have important roles in incorporating manure into the soil profile where it can be decomposed by other biota
