Soil Respiration Pre-lab Quiz

soil is…

biologically active and contains numerous microbes

functions in the soil ecosystem that soil microbes serve

1. Recycling of energy and carbon

2. Recycling of plant nutrients

3. Nitrogen fixation

4. Nutrient/water absorption

5. Disease transmission and control

6. Decomposition of chemical wastes

Recycling of energy and carbon

aerobic decomposition of organic matter releases stored energy and produces CO2, which is then used by plants for photosynthesis

Recycling of plant nutrients

the decomposition of organic matter transforms plant nutrients into available forms that can be taken up by plants

Nitrogen fixation

some organisms take nitrogen from the atmosphere and transform it into organic forms which are then utilized by other organisms in the ecosystem

organisms that use organic nitrogen during nitrogen fixation

bacteria in symbiosis with legume plants, blue-green algae, and some actinobacteria

Which process started the chemical production of N fertilizers in 1909?

the Haber-Bosch process; this N fixation process has been happening for millions of years

Nutrient/water absorption

organisms such as fungi and actinobacteria form associations with plant roots and aid the plant in exploring the soil environment for water and nutrients

Disease transmission and control

some organisms cause or transmit diseases while others, such as Penicillium, produces antibiotics that control disease organisms

antibiotics

products of soil microbes

What produces antibiotics penicillin and tetracycline, respectively?

fungi penicillium, and an actinomycete, called streptomyces

Decomposition of chemical wastes

pesticides, petroleum products, and other organic chemicals are degraded by soil microbes; first into organic intermediates, ultimately into CO2 and H2O

Pesticides that resist microbial action may…

accumulate and lead to environmental pollution.

Respiration and photosynthesis are represented as:

Respiration: C6H12O6 +O2 → CO2 + H2O + ENERGY

Photosynthesis: CO2 + H2O (light) → C6H12O6 +O2 (chlorophyll)

Mineralization equation

mineralization → R-NH2 → ROH + NH4+ → NO3- + energy

Microbial activity in soil is dependent on these factors:

numbers of microbes in soil,

the carbon nitrogen ratio of the organic matter,

soil moisture content,

soil acidity,

nutrient availability,

aeration,

temperature

A gram of soil may contain…

billions of bacteria and many other microorganisms.

Humus

provides a substrate for the existence of many soil organisms (highly resistant to decay

What happens when fresh organic matter is added to a soil?

it provides readily available energy and carbon sources; and microbial numbers and activity rapidly increase; this microbial activity in the soil is directly related to the amount of CO2 produced by microbial respiration

process of soil organic matter decomposition:

organic matter + O2 + microbes → CO2 + H2O + energy + humus + new microbial cells + plant nutrients (N, P, S, etc.)