Soil horizon/profile Flashcards
What is a Soil Horizon/ profile?
An area used to indicate the type of soil in an area
How do you obtain a soil horizon?
Dig a pit and measur the soil depths
Name the horizons typically found
O-Organic/leaf litter layer A-Top Soil B-Sub Soil C-Parent Rock Bed Rock
Describe the leaf litter layer
Has turf/weeds/plant material on it
Describe Top Soil
The part used for crops
A mix of organic matter, gravel, stones, animal and plant waste.
Dark in colour due to presence of humus
Describe Sub soil
Lighter in colour as less humus
Nutients from above layer leached down so more clay like structure
Less soil organism life and less plant roots
What is Humus?
The black jelly that coats soil particles.
Created by broken down organic matter created by soil organisms and bacteria in soil
Gives top soil it’s dark colour
What is weathering?
The break down of rocks by:
Physical-water, wind, heat, frost, glaciers
Chemical: rainfall (carbonic acid)
Biological: action of all organisms-humans and animals and lichens on rocks
How does water break down rocks?
Moving water can carry particles in it.
The faster it moves the more it can carry.
Rocks being carried, knock against each other and those on the river bed so are scoured down.
How does wind break down rocks?
Sand blasting.
Wind carries abrasive particles and they rub against each other.
typically in hot climates
How does frost weather rocks?
In temperate areas.
Water gets into cracks, expands as it freezes, and that pressure forces the rock to crack more
Common in porous rock like chalk and limestone
Glaciers weather rocks how?
Ice sticks to adjacent rocks, the debris in the glacier scours against other material as it moves downhill like a scrubbing brush
What is biological weathering?
The action of plants and animals including humans on rock.
Eg: patches of lichens on rock
Humans mining
List three symptoms that indicate plants are lacking in nutrients
Chlorosis- yellowing of foliage
Stunted growth
Reduced yield/fruiting
Bitter pit in apples that are calcium deficient
Leaves can go purple in tomatoes that lack phosphorus
How can the growth of plants be increased without using fertiliser?
Use of organic mulch-reduces water loss and suppresses weeds
Remove weeds-reduces competition for nutrients, light and water
How can the growth of plants be increased without the use of fertilisers?
Use of mulch-suppresses weeds and retains moisture
Remove weeds-reduces competition for water, light and nutrients
Adequate water supply
Avoid overcrowding
Suitable temperature to induce growth of plant
Name a distinct horticultural situation for the use of the following fertiliser:
Top dressing
Base dressing
Liquid feed
Foliar feed
Top dressing: lawn
Base dressing- tree planting
Liquid feed-tomato’s
Foliar feed- camellias and roses (to overcome lime induced chlorosis)
State two effects of pH on soil structure
Soil organisms cannot decompose OM as efficiently so less nutrients put into soil
Also less soil organisms in general
Flocclation necessary so soil more workable
Describe the use of one named material to raise pH
Lime lowers acidity.
After digging apply 500g per sq metre
Lime isn’t effective on dry soil so must be watered in
Must be incorporated into soil
Use a lime spreader or spread by hand
Must be crushed or in powder form as not very soluble
Carry out liming prior to a crop being sown/planted
What is a benefit of using sulphur?
Easy to apply Measured accurately Fast acting No impact on soil structure Can be slow to act depending on particle size and requires re-application
What is advantage of adding organic matter
Improves soil structure Adds micro-organisms to soil Natural Sustainable The ability of om to lower pH of soil is variable and requires re-application
Describe how the formation of a soil cap can form in the surface of soil
Falling rain or over watering/cultivation caused soil structure to break down.
Lack of Organic matter contributes
More common in fine soil as particles bond together and form a crust when they dry out
As there is nothing to hold the particles together, they fall into the gaps in the soil surface causing them to block so surface water runs off.
List three ways of minimising a soil cap
Water using a rose on watering can -or upturn it.
Avoid working on soil if too dry or rain imminent
Use a layer of Organic matter or mulch to protect surface
Hoe regularly between rows and seedlings
State two effects a soil cap can have on plant growth
Seedlings cant penetrate cap
Water runs off surface , roots cant access water so wilting and poor growth occurs
roots unable to access oxygen as pore spaces in soil are filled
What is meant by a pore space?
Pores are the spaces between the solid matter of soil
Macropores
mesopores
Micropores
What is Available Water Content?
Water available for a plant to uptake and is held on the mesopores
Available water decreases as the volume of air in the soil increases
Saturation Point
This is reached when all the pore spaces in the soil are filled with water
Permanent Wilting Point
No more water available in soil for plant
macropores and mesopores are filled with air
No water available to plant in root zone
Soil moisture deficit
the amount of water required to bring the soil back to field capacity
What is parent material?
The base level of a soil horizon
Has been weathered over vast periods of time
All the smaller, broken down pieces are mixed throughout the top and subsoil
What are the main soil types?
Loam
Sand
Silt
Clay
These are called soil separates
Describe loam
A mixture of sand, silt and clay
Ideal for most crops
Well drained
Aerated with a balance of pore spaces
Describe a sandy soil
particles are 0.05-2.0mm in size
85% or more of sand
No more than 10% clay
Heats up quickly
Short of nutrients-needs watering and feeding often “hungry”
Easily worked-dries quickly/good drainage
Large pores
Feels gritty when wet
Adding OM helps to bind particles together
Describe a clay soil
40% or more clay particles less than 0.002mm in size Holds a lot of water and nutrients poorly drained slow to warm up in spring prone to compaction especiallty when wet Heavy soil, cloddy lumps Feels slippy when wet
How can a clay soil structure be improved?
frost helps break down the large lumps-frost crumb
weathering helps improve structure
Adding bulky OM opens air spaces and improves drainage
Adding Lime helps decrease acidity and encourages it to form crumbs
Describe a silt soil
Micro-sand particles 0.002-0.05mm
Pores are smaller than sand pores
Feels silky/soapy when wet
Reasonable drainage
Holds more moisture than sand-sufficient for plants
Hard to manage as unstable characteristics
What is average composition of soil
water: 20%-30%
Air (pore spaces) 20%-30%
Organic matter: 1%-5%
Mineral matter (From parent rock) 40%-60%
Define a Macropore
Large pore that holds air
Define a mesopore
Medium pore thats holds available water
Define a micropore
Small pore, holds unavailable water (Hygroscopic)
