001 Characteristics, components and Properties of Soil Flashcards
What is the soil food web?
combination of organic matter and the community of organisms that decompose the organic matter in the nutrition
What do the community of organisms in the soil food web do?
They decompose and recycle natural nutrients back into the soil and create humus.
What is the order of the food web?
Primary producers, primary consumers, secondary consumers, third level consumers and then lastly the predators and the decomposers.
What is the 1st trophic level?
The primary producers. The sun’s energy produces photosynthesis which creates carbon and organic compounds which is energy in the form of humus and the active organic matter.
What is the 2nd tropic level? What do bacteria do and what do they release into the soil? Which organisms reproduce in this environment?
Simple soil organisms that decompose the plant material. Bacteria consume the active organic matter and deplete this source of energy while releasing CO2. Organisms such as pathogens, parasites and roof feeders reproduce in this environment.
What is the 3rd trophic level?
Larger soil organisms that feed on the 2nd trophic level organisms. For example shredders, predators, grazers (protozoa, nematodes and arthropods)
What is the 4th and 5th trophic level?
Higher-level predators, feed on smaller soil organisms.
What is Humus? Which type of soil has the most humus?
the organic component of soil, formed by the decomposition of leaves and other plant material by soil organisms. Clay is the richest in humus.
What does humus provide for plants?
Contains nitrogen and it provides it in a form that is highly usable for plants
What are the two types of minerals found in soil?
Primary minerals and Secondary minerals
What are primary minerals?
similar to the parent material, found in sand and silt
What are secondary minerals?
result from the weathering of the primary minerals
What influences the ability of soil to retain important nutrients? What are these atoms called?
Negative and Neutral charges, cations contribute to a soils cation exchange capacity
What is soil texture?
based on the percentage of sand, silt and clay
What is the order of largest to smallest particle in soil?
Largest to smallest -
Sand, Silt, Clay
What is soil water availability?
Capacity of a particular soil to hold water that is available for plant use. The texture changes the available water.
Explain the charges in H2O
The hydrogen atoms are slightly positive and the oxygen atom is slightly negative.
What is Permeability of soil?
Permeability describes how water or other liquids and air are able to move through the soil
Which particles have the highest WHC and which particles have the lowest WHC?
Clay soils have a higher WHC and sand has the least
How does organic matter influence the WHC ?
Organic matter has a high affinity for water, which means it increases the WHC
What is the “wilting coefficient” or “permanent wilting point”?
When the water is bound so tightly to soil particles, it’s not available for plants, overall decreasing the amount of available water.
Which type of soil has a higher wilting point and higher field capacity but more unavailable water? and why?
clay, clay particles have micropores on the surface that hold water tightly making it hard for plants to extract water
What are the two most productive soil textures and why?
Silt and Sand because they hold large quantities of water that is available for plants to use
What is organic matter derived from?
dead plants and animals
What is the importance of organic matter?
it holds on to and provides the essential elements and water for plant growth
what happens to the cation exchange capacity as you add more organic matter to soil?
The CEC increases which allows the plants to be more productive
What three gasses are important for plant growth?
Oxygen, carbon Dioxide and Nitrogen
Why is oxygen important?
essential for root and microbe respiration
Why are CO2 and Nitrogen important?
They are important for underground plant functions such as for nitrogen-fixing bacteria
What happens sometimes after a flood?
There is an excess amount of water which displaces gasses and can prevent root gas exchange which can lead to plant death
Why are microorganisms important in soil?
They are the primary decomposers of organic matter, water and air and then recycle the raw organic matter into humus
What is CEC and what does it mean?
Cation exchange capacity, it is the measurement of negative charges and tells us the soils ability to balance and hold positive charged elements
How can you increase the CEC?
By adding more organic matter, crop rotation or cover crops
Explain soil structure?
the arrangements of soil particles into aggregates (peds) that result from pedogenic process. in other words it is the grouping or arrangements of individual soil particles into a larger grouping
What are the four principle forms of structure?
Plate-like, Prism-like, block-like and round
What is another word for pore space?
Porosity
What is porosity and why is it important?
pore space in soil between mineral particles filled with either air or water. The pore space contains and controls most soil functions
Compare the different textures of soil: Clay, Sand, Silt and Loam
Clay:
heavy, high in nutrients, erosion resistant, wet and cold in the winter, dry in the summer, suffer drainage problems
Sand:
light, dry and warm, need lots of watering, low WHC because it easily drains, low in nutrients
Silt:
fertile, light but moisture-retentive, easily compacted
Loams:
mixture of the three textures and avoids the extremes of each
Why should you add organic matter to clay soils?
it can break down the clay into separate clumps which allows the water and nutrients to be more easily available
Why should you add organic matter to sandy soils?
it increases the nutrients and WHC by binding loose sand into more fertile crumbs
Why should you add organic matter to silt soils?
silt is prone to washing away and wind erosion is left exposed to the elements
Why should you add organic matter to loams?
important to add organic matter mostly if you are digging or cultivating these soils over and over in order to replenish the nutrients
Where can you find clay soils in CA and what kind of commercial crops prefer them?
Southern California
Olive/orange trees
Citrus
Where can you find sandy soils in CA and what kind of commercial crops prefer them?
Near the costal line
Strawberries
Peppers
Zucchini
Where can you find loamy soils in CA and what kind of commercial crops prefer them?
Northern California and the valley
Wheat
Oil seeds
Almond trees (sandy loam)
