Lecture 3 Flashcards
Texture, structure, color and porosity are all ________ properties of a soil
physical
If organic matter in a soil is removed or destroyed, mineral particles of the soil _______
remain
Soil particles are divided into______ based on the_______of the particles
sand, silt and clay, diameter
- Clay has less than ___ diameter
- Silt has between ___ and ___ diameter
- Sand has between _____ and _____diameter
- 2u
- 2u and 60u
- 60u and 2000u
The relative percentages of sand, silt and clay in a soil refers to…….
Soil texture
Texture is loosely described using the…..
fine-course range
Normal soil consists of…..
sand, silt and clay particles
Soil with over 40% clay particles, less than 40% silt and less than 45% sand is described as……
Clay
Soil with between 70% and 90% sand, less than 30% silt and 15% clay is ……..
Loamy soil
Texture can be determined by……
Feel, Laboratory, the use of Textural Triangle or by manipulative
Soil Texture Triangle compares the composition of soil particles to determine the……
soil type
Fine textured soils has more pore space than coarse textured soils because……
You can pack more small particles into a unit volume than larger ones.
Fine textured soil drains slower/faster than as coarse textured soil.
slower
Fine textured soils holds ______water than coarse textured soils.
more
The degree of connectivity between soil pores is known as______
Permeability
A highly permeable soil is one in which water runs through quite readily. True or False?
True
Coarse textured soils tend to have large, well connected pore spaces. Will permeability be high or low?
High
The arrangement of soil parts and pore spaces between then is referred to as……
soil structure
Soil particles are arranged in small rounded units. What is this called?
Granular
Soil particles are arranged to dorm block-like units which are about as wide as they are high or long is called……
Blocky
Blocky soils are common in
subsoil
Soil particles are arranged in plate-like sheets which are approximately horizontal in the soil is
Platy
Soil particle in this type of soil structure are arranged into large peds with long vertical axis.
Prismatic
The greater the degree of aggregation, the ______pore spaces available to ________ to the plant roots.
more, supply air and water
Soil aggregation is important for increasing stability against _______
soil erosion
Soil color reflects an integration of ___________________ processes that have taken place within the soil.
Physical, chemical and biological
Surface soils with high amount of organic matter have __________colors
Black or dark brown (humus)
A surface soil with lighter color can be associated with the __________where most leaching has taken place.
E horizon or Eluviation
Subsoil color also indicates
minerals present
Iron tends to give _______colors
red or yellow bright
Black color in subsoil may indicate the presence of _______
manganese
Color can tell us about drainage. Soils that are poorly drained usually have______colors
grey
The term _______is used when several colors are present in a given soil.
Mottling
Soils which are wet in their upper layers for a long period of time are referred to as ____
Hydric soils
Drainage mottled in hydric soils are termed
Redoximorphic features
Soil color is used to classify various soils of the world into groups. Is this true?
Yes
Black color of the surface of soil way indicate the presence of _______and for that matter a _______fertility.
Humus, high fertility
Dark brown or black soil indicates the soil has _______organic content.
high
Red or yellow soil indicates the presence of what minerals?
Oxidized ferric iron oxides.
Black soil indicates the presence of which mineral?
Manganese oxides
Which mineral makes soil green?
Glauconite
Soil color also gives an indication of _______condition
drainage or moisture
Grey mottles indicate_______
poor drainage
Wet soils are _______ than dry soils.
darker
An iron potassium phyllo silicate mineral if characteristic green color which is very friable and has very low weathering resistance is a ________
Glauconite
The amount of pore spaces between soil particles is referred to as _______
soil porosity
Pore greater than 0.075mm are termed as
macro pores
Pores with equivalent diameter of 0.075 - 0.03mm are termed as
meso pores
Pores smaller than 0.03mm in diameter are called
micro pores
Soil texture and structure influence porosity, true or false?
true
Coarse textured soils have many _______pores
macro
Fine textured soils have more ______ pores.
micro
Fine textures soils have _______total porosity than coarse textured soils.
greater
Due to the dominance of macro pores in coarse textured sandy soils, movement of water and air can be very fast despite its low total porosity. True or false?
True
Fine textured soils especially those without a stable granular structure may have reduced water movement even though they have a large volume of total pore space. Is this true?
Yes
Fine textured soils absorb ________amount of water and their small pore spaces do not allow water to drain freely.
relatively large
Do fine textured soils hold more water than coarse textured soils?
Yes
Not all the moisture retained in clayey soils is readily ________ to plants.
available
As micropores in fine textured clay soils are often full of water, aeration especially in the subsoil can _________for root development.
Inadequate
The properties of soil may vary according to the ……
condition of its formation and the rocks from which it came from.
A granite rock breaks down to form coarse sand which is/is not fertile.
Is not fertile
Basalt rocks breaks down to form clay soil which is or is not suitable for most forms of agriculture. Which is which?
It is suitable
Patent material affects two soil properties namely……..
soil texture and soil color
Granite, a slow weathering rock produces…..
sandy soil
Shale, an easily weathered rock forms……
Clay-rich soils.
Light grey colors in subsoil can be inherited from the parent material……
Quartz
Which patent material imprints a black color to the subsoil horizons?
Basalt
Extreme weathering in warm moist climates (HR + HT) lead to the production of ……
fine textured soils
Climate influences soil texture and contributes to the development soil profile. True of false?
True
Precipitation influences horizon development factors, such as_____
translocation of dissolved ions through the soil by leaching
Time influences soil________
texture, leaching and acidity
Older soils are_____
clayey, more leached and acidic
A soil’s maturity does not only depend on the number of years that it has taken to form. Is this true?
Yes
A soils’s age is determined by______
an interaction between time and the other soil forming factors.
In warm moist climates, soils attain maturity……..slower/faster?
faster
The degree of acidity or alkalinity of a soil is referred to as soil _______
PH
A measure of hydrogen ion (H+) concentration in a soil is referred to as_____
soil PH
PH scales range from
0 to 14
pH values below 7 are considered …..
Acidic
pH values above 7 are considered……
alkaline or basic
Good agricultural soils have a soils pH between
5 and 7
Soil becomes acidic when basic cations like calcium are……
leached from it and replaced by aluminum ions
Soils that develop under high rainfall conditions and abundant vegetative cover tend to be acidic because of……
high rate of leaching and high organic matter content
Acidic soils have _______levels of hydrogen
very high
Acidic soils are good for crop production. True or false?
False
Alkaline soils are sometimes not good for crop production why?
They contain significant amount of sodium that may exceed the tolerances of plants.
The net ability of a soil to hold, retain and exchange cation such as calcium, potassium, magnesium and sodium is referred to as……
Cation Exchange Capacity
Cations are…..
positively charged ions
The finest clay and organic matter particles are referred to as soil…..
Colloids
Colloids are ……. charged.
Negatively
Soil surface has a net …….charge
negative
The negatively charged colloids attract ……… such as Calcium, Potassium, magnesium and sodium to prevent their leaching.
cations or positively charged ions
If there are more electrons than protons, the net charge on the object is …….
negative
A soil with a relatively high Cation Exchange Capacity (CEC) is likely to have a _____organic matter content.
high
A soil with higher CEC is more fertile than a soil with lower CEC. True or False.
True
Soils with higher CEC values tend to have ……. clay and silt particles.
higher
Coarse-textured sandy souls generally have ……….CEC value.
low
Parent materials rich in soluble ions such as magnesium, sodium, potassium, calcium are easily dissolved in water made available to plant. Is this true?
Yes
The soluble ions are…..
Sodium, magnesium, potassium, calcium
If parent material is low in soluble ions, water moving through the soil may remove excess bases and replace then with hydrogen ions, making the soil ……… and …….. for crop production.
Acidic, unsuitable
Soils developed over sandstone are generally…….in soluble bases and …….in texture which promotes leaching
low, coarse
Climate fully determines the type of pedogenic processes. True or False?
False, it only partly determines.
Heavy rainfalls promotes …….. in warm moist climates.
Lacterization
Salinization occurs in ……..
warm and dry environments eg; desert climates
Podzolization occurs in ………. under coniferous vegetation.
Temperate to cold moist climates like the colder part of humid continental subarctic climates.
High summer rainfall and acidic solution from decayed coniferous litter promotes …… of the top soil (A and E horizons)
leaching
The upper portion of a B horizon of …….. is stained ……… due to the accumulation of iron oxides in that zone.
Podzol, reddish color
The laterite soil is formed ……..which leads to soil leaching leaving only oxides of iron and aluminum.
under conditions of high temperature and heavy rainfall with alternate wet and dry periods
Climate partly determines soil ………..as it controls leaching.
pH values
Desert soils have low concentration of organic matter because of …….
scarce vegetation
Bacterial activity is impeded by very low temperatures in the ……… regions
tundra
