Members of this (these) microbial group(s) are responsible for a major proportion of the nitrogen fixed globally in symbiosis with higher plants.
A) actinomycetes
B) bacteria
C) fungi
D) both A and B
E) all of the above
Question 2In most soils the overall population (numbers) of microorganisms changes with time, generally following changes in the:
A) concentrations of antibiotics.
B) pore space.
C) availability of root infection sites.
D) supply of oxygen.
E) supply of decomposable organic matter.
Question 3The fungal symbiont generally benefits from the mycorrhizal relationship by obtaining ________ from the higher plant.
A) micronutrients
B) water
C) phosphorus
D) all of the above
E) none of the above
Question 4Organisms which use carbon dioxide or carbonates for their carbon source and either sunlight or inorganic chemicals for their energy source are called ________.
A) heterotrophs
B) detritivores
C) actinomycetes
D) autotrophs
E) facultative anaerobes
Question 5Light colored surface soils are likely to be warmer than dark-colored surface soils if soil moisture and other conditions are the same.
Indicate whether the statement is true or false
Question 6Soil tilth refers to:
A) the physical suitability of a soil for plant growth.
B) the moisture content at which a soil is best suited for tillage.
C) micro-aggregates produced as a by-product of tillage.
D) the bearing strength of a soil under a given downward force.
E) ratio of bulk density to particle density.
Question 7Which of the following practices is(are) useful in stabilizing surface soil structure?
A) growing grass sod
B) use of green manure crops
C) use of organic mulches
D) minimizing tillage
E) all of the above
Question 8Which of the following groups is not considered to include important primary consumers in the soil ecosystem?
A) saprophytes B) predators C) detritivores D) herbivores E) fungi
Quick Reply
