Soil 309 Flashcards
What three particles is soil made from? Put in order of size largest to smallest.
- sand
- silt
- clay
Name the five layers of soil (soil horizons) from first to last.
- humus
- topsoil
- subsoil
- Weathered rock fragments
- bedrock
Define ‘humus’
The organic component of soil, formed by decomposing leaves and other plant matter that sit on the surface of the ‘topsoil’. It is organic matter after decay.
Define the characteristics of ‘topsoil’
Topsoil is the uppermost horizon of soil. It is the most fertile part of the soil containing the most organic matter & soil organisms. It may be dark in colour due to presence of organic matter and humus. Topsoil depth varies but a good root depth would be 30-60cm.
Define the characteristics of ‘subsoil’
Subsoil is the layer below the topsoil. It will contain little to no organic matter and be lighter in colour than topsoil. Will contain some roots of larger plants like trees.
What are the three MAJOR soil horizons. List first to last.
- topsoil
- subsoil
- parent rock (substratum)
When the primary participles of soil are combined, what is it called?
Aggregates or peds
Describe aggregates and their structure
Aggregates are clumps of soil made up of primary particles (sand, silt and clay). Their varied shapes allows for soil to have pores for air and water
What’s problems can arise if soil gets waterlogged?
It excludes air within the soil affected micro-organisms and earthworms. The soil will warm up slowly in spring and gives poor soil structure.
Soils that are dominated by sand are considered…….
Coarse textured
Soils that are dominated by clay are considered ……
Fine textured
Soils that are strongly influenced by more than one property are considered …..
Medium textured
When mixing a soil sample with water, how will the particles seperate? List in order top to bottom
Larger particles have higher density so will fall to the bottom faster
- humus (floats to the top)
- clay
- silt
- sand
When using the ‘feel method’ to determine soil texture/structure, what qualities determine either sand, silt or clay soil?
- sand soil will feel gritty between your fingers
- silt soil when wet will feel smooth, not very sticky
- clay soil will feel very sticky and can be moulded into shape easily
What causes soil compaction and what are the effects?
Soil compaction is a result of compression of the soils pores that would otherwise transport water and air. It is caused by using heavy machinery, heavy foot fall over an area of use of incorrect tilling methods. It destroys soil structure, soil drains slowly and impedes tooth growth.
What are the characteristics of ‘organic matter’
Organic matter is made up of dead and decaying plants, animal waste which releases nutrients during decay. It retains moisture and lots of nutrients.
What are the effects of organic matter in soil?
Organic matter contributes to plant growth through its effects on the physical, chemical and biological properties of the soil.
How does organic matter decompose?
Decomposition is largely a biological process that occurs naturally. Detritivores such as earth worms feeding and decomposes such as bacteria and fungi.
What 5 products are released during the decomposition process?
- Carbon dioxide
- energy
- water
- plant nutrients
- resynthesized organic carbon compounds
What are the Benifit of living organisms (worms,bacteria,fungi) in soil?
They decompose organic matter. They improve soil aggregation, which influences soil-water movement and aeration. They enhance nutrient levels. They are essential in developing soil organic matter.
How much soil does a tree need?
2 cubic meters of soil for every 1 square metre of crown projection (crown projection is how far the branches come out)
What problems occur is soil drys out?
Plants in dried out soil will change colour, soil will harden, soil compaction can occur easily, weeds can germinate on bare soil exposed, moss can develop abs it can stunt growth.
When evaluating a site for landscaping what factors should be considered when thinking about the growing media (soil)?
- soils pH
- soils nutrients
- pollution (fumes, dust, lights)
- drainage problems
When evaluating the surrounding environment before landscaping a site what factors should be considered?
- shaded areas
- site aspect
- frost pockets
What methods are used to measure a site?
- Measuring with a tape
- trundle wheel
- 3.14 x r2 (areas of a circle)
- New technology (drones, GPS mapping)
What does the PH scale range from?
1-14
On the PH scale define what the lowest to highest numbers represent.
1 = acidic 7 = neutral 14 = alkaline
What is the main control factor in soil?
Calcium
How do you raise PH levels in soil to make it more alkaline
Add lime (granular or powder)
How do you lower PH to make it more acidic?
Add fertiliser or ammonium sulphur, sphagnum peat or organic mulch
Define ‘loam’
Loam is soil composed mostly of sand, silt, and a smaller amount of clay. its mineral composition is about 40–40–20% concentration of sand–silt–clay
What is Soilless Mix?
A soilless mix might look like soil, but it doesn’t contain any inorganic matter (sand, clay, silt, etc.). It’s a mixture of organic materials like peat moss, coconut coir, wood chips, perlite, or vermiculite. There might also be a slow-release fertilizer in there as well.
What is John Ennis compost?
Most potting compost or media offered is soil-less and either based entirely on peat, has some peat in its formulation or is peat-free. There are advantages, however, to soil based media and John Innes mixes are widely used.
John Innes Potting Composts
a) Soil mix
7 parts by loose volume medium sterilized loam
3 parts by loose volume peat substitute
2 parts by loose volume coarse sand
What are the main organisms in soil?
Bacteria, actinomycetes, fungi, algae, Protozoa, nematodes
