1. Thursday’s Quiz will Cover:
Intro to soil lecture (last Thursday)
Soil Article (last Thursday)
Chapter 9 Reading Guide and Soil Topography Questions (Last Friday)
Soil Organisms (Decomposers) Lecture (Today)
Vermiculture Reading Questions (Today)
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Side note: Final will cover soil lab and tomorrow’s lecture and Friday’s webquest as well.

2. What kinds of plants and animals live in the soil?
1) Bacteria: most numerous and important
can reproduce in minutes and may decrease rapidly in unfavorable conditions
a soil which has 5% O.M. can have 3 1/2 tons of bacteria per acre (ability to multiply quickly)
anaerobic bacteria (do not need free oxygen) get their oxygen from chemical reactions

3. What kinds of plants and animals live in the soil?
2) Actinomycetes: type of bacteria, but some resemble molds
can live under drier conditions than other bacteria, abundant in sod
among the most important agents of the soil in the breakdown of dead plant materials, including cellulose
responsible for characteristic smell of freshly tilled soil

4. What kinds of plants and animals live in the soil?
3) Fungi: most are too small to be seen by the naked eye, except for yeast, molds, mushrooms, puffballs, and toadstools
fungi do not have chlorophyll and must get their food from organic substances
Type of organic matter in soil determines type of fungi that will prevail
Secrete substances that aid in the formation of soil aggregates – glomalin or “soil glue”
Continue the decomposition process after bacteria & actinomycetes have ceased to function

5. What kinds of plants and animals live in the soil?
4) Algae: contain chlorophyll
ex: seaweed, scum-forming algae on ponds
soil algae are too small to be seen with the naked eye, but in large numbers can give soil surface a green color
favor damp soil that is exposed to the sun
believed to be able to fix free nitrogen from the air in the soil, valuable to rice production
Some symbiotic algae associate with one of several fungi in forms called “lichens” (help weather rock surfaces)

6. What kinds of plants and animals live in the soil?
5) Protozoa: minute animals found in the soil, smallest form of animal life
must live in a water film

7. What purpose do microorganisms have?
decay plant residue (straw etc.)
make free nitrogen in the air available to plants
break down nutrients needed by plants
break down cellulose
much of the food in the soil is not available to the plant, until microbes break them down

8. What is Nitrogen Fixation?
the process of changing free nitrogen from the air into plant useable nitrogen by bacteria
two types of nitrogen fixing bacteria:
1) attached to the root
nodules of legumes
2) live freely in soil
(rare)

9. How do Nitrogen Fixing nodules form?
bacteria enter the single-celled root hairs where they multiply rapidly due to favorable conditions, the colonies then form into nodules, usually in bunches

10. How much nitrogen is added to the soil by bacteria?
free soil bacteria add lbs./yr.
nodule bacteria add lbs./yr.
may not be a net gain due to nitrogen in harvested crop
gene splicing may yield a corn plant with nitrogen fixing qualities. This would save the producer money and reduce the need for petroleum (most commercial fertilizers are made from petroleum)

11. What are some of the harmful effects of soil microorganisms?
bacterial diseases: potato and tomato wilt, mildews, blights, dry rot
microbes compete for food with the crop, if there are any shortages of nutrients this could harm the plant

12. What are favorable conditions for soil microorganisms?
food, temperature, moisture, acidity, and aeration: most are similar to plants
most are injured by direct sunlight except algae (chlorophyll)

13. What best management practices (BMPs) can help soil biota?
Conservation Tillage-increased soil stratification and size and activity of soil organism populations under conservation tillage compared to conventional tillage leads to increased nutrient retention.
Crop Rotation-increases microbial diversity

14. What are some of the higher forms of animal life in the soil?
slugs & snails: feed on the surface, favor damp shady conditions
arthropods: insects (ants, centipedes) most feed on decaying O.M.
nematodes: (microscopic, unsegmented worms) abundant in soils, three groups:
1) feed on plants
2) feed on other life forms

15. What are some of the higher forms of animal life in the soil?
Earthworms
Feed on decaying O.M. (earthworms) up to 500 lbs per acre, aerate soil, allow water to penetrate, excrement is good plant food

16. What are some of the higher forms of animal life in the soil?
Rodents, gophers, squirrels, prairie dogs: most are considered a nuisance.
Burrows are similar to those of worms, but can be a menace

17. How to plant roots benefit the soil organisms?
plant roots hold down surface soil
break up subsoil
provide O.M.
add minerals, air, and water
channels for air & water penetration
loosen soil

18. EXIT SLIP Name 5 types of microorganisms present in soil?
What functions do soil microorganisms perform?
What is nitrogen fixation?
Where does the majority of nitrogen get fixed?
What BMPs help soil organisms? How?