Practice Questions Flashcards
How to increase organic matter levels in soil?
Organic manures
Cover crops
Biomaterials
Mob grazing
Grass leys
Compost
Crop residues
No till systems
Companion cropping
Countryside stewardship/landscape recovery
Soil management plan - SOM testing
Bacteria in the nitrogen cycle and why it’s important to have good soil health
N fixing - Azotobacter, rhizobacteria in legumes (Mutualistic symbiont)
Proteobacteria eg nitrobacter = nitrification
Decomposers of OM - Actinobacteria
Pseudomonas = denitrification
Prey for nutrient cycling
CN ratio
Pathogens - Pectobacterium for black leg
Structure - aeration, drainage, OM (food source), pH
How soil health improved NUE
Physical: structure - pores and aggregates, compaction, reduce leaching, drainage, CN residues
Chemical: OM for CEC, pH, regular soil testing
Biological: OM - structure, drainage, pores, bulk density, microbial activity - nutrient cycling, symbiosis, earthworms - structure and root channels
Benefits of OM
Soil structure - bulk density, pores, CEC allowing flocculation
Drainage
Nutrient release
Carbon store
Increased microbiota
Less erosion due to structure
Water holding capacity
What is CEC and how it differs between soils
CEC is total exchangeable cation sites in a soil.
Clay and humus have negative charged surfaces which attract positive cations such as Ca2+ which allows flocculation between aggregates and an improved soil structure
Sands do not have a high CEC due to lack of clay particles
Clay particles have a high surface area also increasing CEC
Role of fungi in the soil and how it impacts plant growth
Mutulistic symbiosis with plants (P for sugars) - mycorrhizal - ecto o arbuscular
Soil aggregation - hyphae, glomalin
decomposers - saprotrophs
Pathogens - fusarium, oomycetes
Release and recycle of nutrients - prey for micro and meso fauna
Predation of nematodes
What is pH and its importance
Conc of H+ ions
Negative logarithmic scale - higher conc lower pH, lower conc higher pH.
7 neutral, below acidic, above alkaline
Comes from oxidation of N, root resp, OM
Affects nutrient availability - lack of Ca at low, lack of Mn at high
Diseases - club root at low, common scab at high
Microorganism activity
Al and Fe toxicity
P lock up
What is denitrification and how to reduce
Conversion of nitrates to nitrous oxide by Pseudomonas bacteria sp in anaerobic conditions
Greenhouse gas
Inefficient use of N
Waterlogged and compaction
Maintain aerobic conditions - good soil structure, OM, drains
Nutrient management plant
CN ratio
Variable application
Crop rotation
Microbiota diversity
pH for NUE
Main soil horizons in a soil
O horizon - organic layer at the top
A - topsoil
B - subsoil
C - substratum
R - bedrock
What is expected to be seen in a well structured soil
a mixture of aggregates
mixture of pores
Lack of stress
Stability - no erosion or slaking
Good friability - tilth
Good soil aggregation between micro aggregates making macro aggregates
Good drainage
microbial activity
micro, meso and macro fauna diversity
aerobic conditions - no nitrous oxide release
Water capacity and its importance
amount of water held in soil
friability, plastic limit, liquid limit
field saturation, field capacity wilting point
plant available between field capacity and wilting point in macro and meso pores
major, secondary and micro nutrients
major = NPK
secondary = Ca, Mg, S, (Na)
micro = B, Mn, Ni, Mo, Cu, Zn, Co, Fe, Se
Difference is importance to plants
What is Humus and how does it influence soil particles
Humus is decomposed detritus
made up of Fulvic acids, humid acids and humins
water holding, soil structure, stability, CEC, nutrient release
Soil food web
microorganisms - bacteria, fungi, archaea
microfauna - protozoa, nematodes, rotifers
mesofauna - tardigrades, mites, springtails
macrofauna - centipedes, millipedes, earthworms, beetles
what is the rhizosphere and processes
soil area around the root strongly related to root interactions
water uptake
nutrient uptake
mutualistic symbiosis
Pathogens
root respiration
root herbivore - cabbage root fly larvae
3 ecotypes of worms and importance
epigeic - litter dwellers begin to decompose detritus
endogeic - horizontal burrows
anecic - deep burrows
Symbiosis 2 examples
mycorrhizal bacteria
rhizobacteria in legumes
causes and effects of compaction
traffic, poaching, poor structure, heavy rainfall
anaerobic conditions
no pores for water and nutrient uptake
poor workability
no root growth
no drainage or infiltration
loss of habitat
important soil properties and characteristics for crop growth
friability - tilth
contains nutrients
structure for root growth
microbial activity
OM
CEC
pH
drainage/infiltration
mix of pores and aggregates
