How human activities affect soil fertility Flashcards
what is soil?
loose surface material that covers most land
what is a fertile soil
a soil that has the nutrients to sustain plant growth and provide plant habitat that results in sustained and consistent yield
what factors can affect soil fertility?
Ability to hold water
Nutrients and minerals
Good air content
relatively neutral pH
Dead organic matter
Soil depth
High levels of soil biota
soil structure
soil texture
what is soil texture
the characteristics of a soil based on the proportion of the mineral particles that are sand silt and clay
what are the sizes of the soil mineral types (big to small)
Sand
Silt
clay
what is the pore size of sand
macro
what is the pore size of silt
medium- (meso)
what is the pore size of clay
micro
what is soil structure
how the particles are arranged within the soil
what is the structure of sandy soils
rounded grains that don’t lock together so the sandy soils drain more freely
what is the structure of clay soils
‘platy’ particles and as they have long flat sides the clay ‘locks’ preventing good drainage
why is soils ability to hold water important
water is necessary for all animals and invertebrates
water is needed for the process of photosynthesis
water is also how plants absorb nutrients in ionic form
what is the problem with water logged soil
prevents air from reaching the plants and organisms creating an anaerobic environment and a less fertile soil
what are some macro nutrients? (main 3)
nitrogen
potassium
phosphorus
what are some micro nutrients
copper
iron
magnesium
manganese
why is it important that heavy metals are not absorbed by soils?
as they are toxic they would harm plant and animal life reducing soil fertility and the overall biodiversity of the area that is contaminted
why is good air content needed in soil?
important for decomposition which breaks down waste into nutrients
why is a neutral pH needed? (soil fertility)
acidic conditions cause damage to plant membranes and can leach nutrients out of the soil
what is the best pH range
5.5-7
what is the problem with alkaline conditions
macronutrients become insoluble making it difficult for plants to absorb them
why is dead organic matter important? (soil fertility)
DOM releases nutrients when decomposed
leaf litter and other matter increases the soils ability to hold water
why is soil depth important
deeper soils hold water for longer and dry out less rapidly don’t get water logged as easily allow plants enough root space needed for growth and stability
What are living organisms found in soil called
Soil biota
What are soil biota important
They process DOM and convert it into nutrients and aerate the soil
What are mycorrhizal fungi
Part of a symbiotic relationship with plant roots important for the absorption of phosphate get glucose in return
What are decomposes? (Generally)
Broad category that includes fungi and bacteria
How do decomposers decompose
They release enzymes that digest the DOM
Require detritivores to break up the DOM to make it easily digestible
What are detritivores? (species examples)
Insects and invertebrates such as worms, millipedes, slugs and wood lice.
What do detritivores do?
Break up larger DOM into small pieces and release the nutrients into the soil
What is the double benefit of worms?
They create tunnels and burrows that allow air to circulate and breakdown DOM
Why are nitrogen fixing bacteria important
Important in converting gaseous forms of nitrogen to ammonium ions
Why are nitrifying bacteria important?
Important in oxidising ammonium ions (animal waste) to nitrate ions which are important or plant growth
How do humans aerate the soil
Done by ploughing and putting in drainage
Making conditions favourable for worms
Why is aeration important?(bacteria)
The soil is more aerobic which allows nitrogen fixing bacteria to exist and convert gaseous nitrogen into ammonium ions helps add nitrogen needed for growth into the soil
Why is aerobic soil important for decomposers
Decomposers do not usually tolerate anoxic or anaerobic conditions
What are the three ways a farmer can add nutrients to the soil?
Add organic matter
Add inorganic nutrients
Increase the rate of nitrogen fixing bacteria
What is adding organic matter to the soil
This means adding manure or animal waste products to the soil
What is adding inorganic material to the soil?
Adding artificial (man made) pellets of nitrogen, phosphorus etc
How can farmers help to increase the rate of nitrogen fixing bacteria?
Planting legumes (peas and beans) which naturally add nitrogen rather than taking it away
What happens to soil fertility on land which is farmed?
Soil becomes infertile overtime and looses structure and ability to hold nutrients because farming degrades soil as soil erosion is increased
What is irrigation?
This is the addition of water to the soil to help plants grow
Why is irrigation important?
Plants still need water for photosynthesis even if in nutritious soil
Water carries the dissolved nutrients in ions the plants take the ions up through their roots without water the nutrients couldn’t be picked up
What is bulk density
The weight of a soil in a given volume
What amount of bulk density restricts root growth
1.6g/cm*3
What soils are more prone to high bulk density
Sandy soils as they are more easily compacted
What causes high bulk density
Heavy machinery or trampling by livestock like cattle
What happens to soil pH over time
Can become more acidic
What can increase soil acidity
When plant material is removed alkalinity is removed
When grain pasture and animal products are harvested the soil is left more acidic
How can soil acidity be reduced
Adding lime or chalk
What is the structure of a silty soil?
granular material of a size between sand and clay and composed mostly of broken grains of quartz
