Soils Quiz 5
What are the two plant available forms of nitrogen in soil solution?
organic and inorganic forms in the soil Fixation Violitization
What are the three main environmental issues with soil/soil fertility and water?
serpentine soils calcareous soils
What kinds of soils and management practices are most likely to result in potassium deficiencies?
serpentine soils calcareous soils
What are the three components of soil organic matter?
small (fresh) plant residues and small living soil organisms, decomposing (active) organic matter, and stable organic matter (humus)
What is luxury consumption?
the absorption of nitrogen or potash from the soil by a crop in excess of crop needs
humus
the organic component of soil, formed by the decomposition of leaves and other plant material by soil microorganisms.
What are the visual symptoms of nitrogen deficiency?
wiltling loss of green coloration Visual Toxicities -Ammonium toxicity (urea burn) causes light brown scorching -Nitrate toxicity causes tan colored scorching.
decomposition
(Redox) reactions chemically convert hazardous contaminants in soils to non-hazardous or less toxic compounds.
oxidation
(Redox) reactions chemically convert hazardous contaminants in soils to non-hazardous or less toxic compounds.
What imbalance in plant nutrients occurs with serpentine-derived soils?
-low calcium-to-magnesium ratio -lack of essential nutrients such as nitrogen, potassium, and phosphorus -high concentrations of nickel and chromium (more common in ultramafic rocks).
What are the four fates of mineralized plant nutrients?
1. Plant Uptake 2. Leaching 3. Adsorption 4. Immobilization
Name three things that can cause changes in organic matter content.
1. infiltration 2.evaporation 3.storage capacity
Name three functions of nitrogen in plants.
1.Essential element for all amino acids 2.Nucleic Acid "DNA" forming 3.Chlorophyll
Name three primary minerals in which potassium is found.
1.Feldspar 2.Mica
What is the C:N that is generally considered to be the dividing line between N immobilization and mineralization?
C:N < 25:1 Sufficient N available for decomposition Some N soon becomes available for plant uptake In general, there is rapid decomposition C:N > 25:1 More competition for N by soil microorganisms, plants suffer N deficiency Decay can be slowed if less than adequate pool of N for microbes
mineralization
C:N < 25:1 Sufficient N available for decomposition Some N soon becomes available for plant uptake In general, there is rapid decomposition decomposition or oxidation of the chemical compounds in organic matter into plant-accessible forms.
immobilization
C:N > 25:1 More competition for N by soil microorganisms, plants suffer N deficiency Decay can be slowed if less than adequate pool of N for microbes conversion of inorganic compounds to organic compounds by micro-organisms or plants, by which it is prevented from being accessible to plants.
What kinds of higher plants does each mycorrhizal group associate with?
Ectomycorrhizae (ecto = outside) Woody plants, mainly conifers and some others Pines, spruce, fir, birch, myrtle, oak, beech, eucalyptus Endomycorrhizae (endo = inside) - Most agronomic crop most vegetable families, grapes, apples, citrus cotton, wheat, potatoes, soybeans - Trees - redwoods, cedar, cypress, coffee, cacao - 85% of vascular plant families have an association Ericaeous - Rhododendrons, blueberries, heather Arbutoid (ectoendomycorrhiza)- Pacific madrone, manzanita Orchidaceous - orchids - important for tiny seeded plants with little nutrient reserves
four different groups of mycorrhizae are found in soils
Endomycorrhizae Ectomycorrhiza Ericaeous Orchidaceous
What disease of ruminant animals is caused by insufficient amounts of Mg?
Grass tetany or hypomagnesemic tetany, also known as grass staggers and winter tetany, - a metabolic disease involving magnesium deficiency, which can occur in such ruminant livestock as beef cattle, dairy cattle and sheep,[1] usually after grazing on pastures of rapidly growing grass, especially in early spring.
How does carbon storage in soils rank among these?
Histisols=47% Andisols=6% Mollisols=2.4% Spodosols=2.0%
What are the three components of soil organic matter
Mineral Matter Organic Matter Air and Water small (fresh) plant residues and small living soil organisms, decomposing (active) organic matter, and stable organic matter (humus)
What are the two types of fixation that occur with nitrogen?
Physical Nitrogen Fixation and Biological Nitrogen Fixation
How is soil organic matter different from humus?
SOM includes all fractions of organic material in it's multitude of stages of degradation, whereas humus is only the humic substances present at the end of the biological degradation of organic matter.
What organic compounds are found in soils? (see Fig. 12.4 , p. 499) Which break down most readily? Which are the most resistant?
Starches,Sugars=rap Protiens Hemicellulose Cellulose Fats,Waxes Lignins,Polyphenols=slow
What is allelopathy?
a biological phenomenon by which an organism produces one or more biochemicals that influence the germination, growth, survival, and reproduction of other organisms.
What is chlorosis?
abnormal reduction or loss of the normal green coloration of leaves of plants, typically caused by iron deficiency in lime-rich soils, or by disease or lack of light.
humification
dead organic matter (leaves, twigs etc) is converted to humus by the action of decomposers such as bacteria and fungi.
What are the two predominant plant available forms of phosphorus in soils?
dihydrogen phosphate hydrogen phosphate
What are the morphological structures/features of endomycorrhizae and ectomycorrhizae?
ectomycorrhizae: Mantle is outside cells Hyphae occupy space between root cortical cells Form a Hartig net between epidermal and cortical cells Most for aboveground or underground fruiting bodies endomycorrhizae: Development of highly branched structures within root cortical cells Arbuscules - facilitate nutrient transfer Vesicules - storage structures - Usually produce single spores in the soil for reproduction, not large fruiting bodies
In what specific kind(s) of clay minerals is potassium fixed in a slowly available form? Why is it fixed in this kind of clay mineral?
inner layer 2:1 clay, vermiculite,micas