Soils and Plant Nutrition

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Questions and Answers

What are the primary components that make up soil?

Water, minerals, gases, living organisms

Rocks, air, nutrients, chlorophyll

Sand, clay, silt, organic matter

Lithosphere, hydrosphere, biosphere, atmosphere (correct)

Which element is not required for photosynthesis?

Nitrogen (correct)

Chlorophyll

Water

Oxygen

How deep can soil typically be found?

Up to 10 meters deep

Up to 2 meters deep

Up to 5 meters deep

Up to 1 meter deep (correct)

Why are plants important for maintaining the atmosphere?

They absorb carbon dioxide and release oxygen. Signup and view all the answers

What is the primary role of soil for plants?

To supply nutrients and water for growth Signup and view all the answers

What do plants primarily produce through photosynthesis?

Simple carbohydrates Signup and view all the answers

Which component is NOT part of the biosphere in relation to soil?

Air particles Signup and view all the answers

What is the significance of chlorophyll in plants?

It allows for photosynthesis. Signup and view all the answers

What do mottles in the soil profile indicate?

Oxidized iron or rust due to drainage issues Signup and view all the answers

Which is NOT a basic characteristic used to describe soil?

Density Signup and view all the answers

What do aggregates in soil consist of?

Compounded lumps of smaller soil particles Signup and view all the answers

How can soil layers be differentiated based on their colour?

Colours help identify distinct layers and their composition Signup and view all the answers

What does the presence of yellow and red mottles typically indicate?

Oxidized iron presence due to drainage issues Signup and view all the answers

What colour is typically associated with salt accumulation in soil?

White Signup and view all the answers

What is the correct range of particle size for sand?

Between 2.0mm - 0.05mm Signup and view all the answers

Which component of soil has very small particles and is known for being sticky and plastic?

Clay Signup and view all the answers

How does silt typically feel when touched?

Floury Signup and view all the answers

What term is used to describe the relative proportions of sand, silt, and clay in a soil?

Soil Texture Signup and view all the answers

Which characteristic best describes the mineral content of soil?

Inorganic components contributing to its fertility Signup and view all the answers

What does the Munsell Colour Chart help determine in soils?

Soil colour Signup and view all the answers

Which of the following indicates a soil that has experienced extensive weathering?

Red/yellow colour Signup and view all the answers

What is soil structure primarily defined by?

The arrangement of soil particles into aggregates Signup and view all the answers

What is primarily used to determine soil texture?

Sieve analysis Signup and view all the answers

Which factor contributes to the creation of soil structure in nature?

Biological activity Signup and view all the answers

Which of the following represents a soil class with a predominance of sand?

Sandy loam Signup and view all the answers

What is the role of organic material in soil structure?

Provides stability and adhesion between soil particles Signup and view all the answers

How does the size and shape of soil aggregates affect soil characteristics?

Affects aeration and water movement Signup and view all the answers

What analysis method is used to determine silt and clay content in soil?

Sedimentation - hydrometer analysis Signup and view all the answers

How is the textural class of soil determined?

By plotting results on a textural triangle Signup and view all the answers

Which of the following is NOT a characteristic associated with soil texture?

Horizontal layering of soil Signup and view all the answers

Which soil has a medium texture according to the classifications provided?

Clay loam Signup and view all the answers

What is the impact of pore size on soil's water movement?

Smaller pores enhance water retention Signup and view all the answers

Which inorganic compounds are mentioned as contributing to soil structure?

Calcium carbonate, iron and aluminum oxides Signup and view all the answers

What is a key factor that influences root penetration in soil?

Soil compaction Signup and view all the answers

Study Notes

Soils

Soils are natural media that supports plant growth
The soil is a thin layer up to 1 meter deep
It contains elements of the lithosphere, hydrosphere, biosphere, and atmosphere
Plants need water, nutrients, and light for photosynthesis
Only plant cells with chlorophyll can photosynthesize
Plants produce simple carbohydrates (CHO) which are either used or stored
CHOs provide nutrients containing carbon, hydrogen, and oxygen.

Soil Variability and Characteristics

Soils are variable in tilled and natural landscapes.
Important to understand different soil types.
This requires recognizing basic characteristics and describing them.

Soil Profile

Layering is evident in thickness and number of layers.
Color distinguishes layers and their borders.
Different colors indicate different layers and their composition.
Stones indicate coarser material, their depth and frequency.
Aggregates are compounded lumps formed from smaller soil particles.
Mottles are areas of color distribution in the soil profile, often yellowish or reddish tones.
- These colors indicate oxidized iron (Fe) or rust.
- This is associated with drainage or oxygen (O2) penetration.
- Uneven distribution of water (H2O) or O2 in the soil can cause this.

Basic Soil Description

The four basic descriptors of soil are color, texture, structure, and horizons.

Soil Color

Indicates soil content.
Brown suggests iron (Fe).
Red or yellow indicates extensive weathering and iron oxides.
Black indicates organic matter (also dark brown).
Blue or grey indicates wet soil and reduced iron and manganese.
Mottles are blotches of red/yellow mixed with blue/grey.
White indicates salt accumulation, common in arid regions.

Color Components

Three components define color: hue, value, and chroma.
Hue is the spectral color.
Value indicates light/darkness.
Chroma indicates purity or greyness.
The Munsell Color Chart helps determine the exact color of soil in labs.

Physical Nature of Soils

The mineral/inorganic component of soils consists of sand, silt, and clay.

Soil Sand

Soil particles between 2.0 mm - 0.05 mm in size.
Can be rounded or irregular/angular in shape.
Cannot be molded.
Low water holding capacity, large pore spaces between sand grains.

Soil Silt

Soil particles between 0.05 mm and 0.002 mm in size.
Irregular shape.
Typically a clay film covers the particle.
Has some stickiness and absorption qualities.

Soil Clay

Particles smaller than 0.002 mm in size.
Very small particles with a large surface area to volume ratio.
Very sticky and plastic.

Soil Texture

The relative proportions of sand, silt, and clay in a soil determine its texture.

Soil Texture by Feel

Sand feels gritty.
Silt feels floury.
Clay feels sticky and pliable.

Soil Texture Determination

Texture can be estimated using the feel test.
Lab determination of relative proportions is done through particle size analysis.
Sand sizes are analyzed with sieves.
Silt and clay contents are determined through sedimentation using hydrometer analysis.

Soil Textural Class

A name assigned to a group of soils with similar sand, silt, and clay ranges.
Determined by plotting the results of particle size analysis on a textural triangle.
Clay is fine texture, silt is medium texture, and sand is coarse texture.

Significance of Soil Texture

Many chemical, nutritional, and physical properties are assessed through particle size.
Influences pore size, water availability, water movement, aeration, root penetration, surface area, and nutrient holding capacity.

Soil Structure

The arrangement of individual soil particles into definable aggregates, or peds, is classified based on size, shape, and distinctness.

How Structure is Created in Nature

Wet/dry cycles, freeze/thaw cycles, biological activity, and cultivation all contribute to forming soil structure.

Structure Stabilization

Organic material plays a key role in stabilizing structure.
- Decomposition products contribute adhesive properties that bind smaller soil particles.
- Root secretions also help create aggregates.
Fine roots and root hairs contribute to stabilization.
Inorganic compounds, such as calcium carbonate (CaCO3), iron oxides (Fe), and aluminum oxides (Al), also play a role.
- Some salts can promote compaction, which is undesirable.

Significance of Texture and Structure

Soil texture and structure impact porosity, pore size, aeration, water movement, root growth, and erosion.

Soil is 3D

Soils have horizontal layers that show how they develop.
Understanding these layers is key to understanding the process of soil formation.

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Description

Explore the essential role of soils in supporting plant growth. This quiz delves into the composition of soil and its critical elements, including how plants utilize water, light, and nutrients for photosynthesis. Test your knowledge on the relationship between soils and plant health!