Module 6

Question 1

how do you improve soil quality and promote environmental quality?

Answer 1

incorporating organic matter into soils

Question 2

what does organic residues on soil surface protect the soil from?

Answer 2

erosion and compaction

Question 3

what happens when soil organic matter is decomposed and incorporated within the mineral soil?

Answer 3

• improves soil quality by promoting soil structure and increasing water infiltration

Question 4

what is soil organic matter composed of?

Answer 4

• primarily carbon
• exists in a continuum of decay

Question 5

what is responsible for soil organic matter formation?

Answer 5

soil microorganisms
- serves as food for microorganisms

Question 6

defining features of the A horizon

Answer 6

soil organic matter
- dark and brown in color

Question 7

how much organic matter can the surface layer of soil contain? what is typical of mineral soils?

Answer 7

• 20%
• 1 - 5%

Question 8

in what ways can soil organic matter change the property of soils?

Answer 8

• soil color, CEC, and water holding capacity

Question 9

If we are adding organic matter to soils to improve soil quality, what should be our target amount?

Answer 9

As a rule of thumb, we target 5% soil organic matter in the top 6 to 12 inches of the soil A horizon.
However, sandy Florida soils are an exception to the rule. Soil organic matter has a high surface area, and is sometimes referred to the glue necessary to bind soil particles together and create soil structure

Question 10

organic soils

Answer 10

histosols
- found in south florida and in everglades

Question 11

a small fraction of soil organic matter is composed of living animals, what are they?

Answer 11

earthworms, mites, nematodes, and soil microbes

Question 12

-how much of non-living organic matter is composed of decomposing organic material?

Answer 12

around 15%
- the material is more uniform in appearance and it’s darker in color than the original fresh residues
- considered active and unstable

Question 13

what do we mean when organic matter is unstable?

Answer 13

• losing mass rapidly though decomposition and still undergoing constant changes in its chemical structure

Question 14

what is decomposition?

Answer 14

mass loss

Question 15

what happens as microbes decompose organic matter?

Answer 15

they break carbon bonds and produce carbon dioxide

Question 16

what drives mass loss?

Answer 16

carbon dioxide

Question 17

how much of the carbon stored within the soil is stored in a stable fraction?

Answer 17

65%

Question 18

how does soil organic matter improve soil quality for crop production?

Answer 18

changes in the biological, chemical, and physical composition

Question 19

the more diverse the biological community…

Answer 19

the more resilient it is to disease, stress, and disturbance

Question 20

how can SOM improve soil structure?

Answer 20

• cause it to clump and form soil aggregates
• With better soil structure, infiltration increases and improves and the soil’s ability totake up and hold water increases

Question 21

organic matter can absorb and hold how much of its weight in water?

Answer 21

90%

Question 22

what is a major storer of global carbon?

Answer 22

soil

Question 23

the carbon cycle moves carbon between what?

Answer 23

the atmosphere, vegetation, soil, and then back to the atmosphere

Question 24

decomposition

Answer 24

the flux that moves carbon from the vegetation to the atmosphere as CO2 and to the soil as organic matter

Question 25

what is the most important flux of the carbon cycle?

Answer 25

photosynthesis

Question 26

the carbon cycle not only moves carbon but also what?

Answer 26

the movement of energy that is required for life above and below ground. The source of energy is the sun, and the sun's energy is stored in the carbon to carbon bonds and plant biomass, and soil organic matter.

Question 27

flux of photosynthesis

Answer 27

- converts gas to CO2 into a solid - sugar - stores energy from the sun within the carbon-carbon bonds of sugar

Question 28

how is photosynthesis measured in the field?

Answer 28

measure how much weight or mass a plant has put on within the time frame of one year

Question 29

reverse photosynthesis

Answer 29

respiration and decomposition

Question 30

what are some ways carbon is released back into the atmosphere?

Answer 30

- use sugars fixed by leaves during photosynthesis - decomposition

Question 31

at what temps is microbial activity higher?

Answer 31

warmer temperatures

Question 32

what conditions slow decomp?

Answer 32

saturated conditions

Question 33

why is decomposition incomplete?

Answer 33

- not all biomass is sugar - not all organic biomass is transferred to CO2

Question 34

composting

Answer 34

the biological decomposition of organic constituents under controlled conditions to form a stable humus-like product. The process occurs quickly as the conditions for microbial activity are optimized.

Question 35

first phase of composting

Answer 35

- mesophilic phase both aerobic and some anaerobic activity

Question 36

second phase of composting

Answer 36

- thermophilic phase - hottest phase - water within the pile is release as steam - fungi replace bacteria

Question 37

third phase of composting

Answer 37

- temp starts to cool - fungi are replaced with filamentous bacteria and a few types of mold - as the pile cools, invertebrates and worms move in

Question 38

phase four of composting

Answer 38

- dominated by larger soil organisms that mix and shred the remaining material and feed upon the bacteria from the previous phase - now ready to by transported and applied to the soil

Question 39

when does composting occur most easily?

Answer 39

- high nitrogen materials are mixed with high carbon materials - 25-40 parts of carbon for every part nitrogen

Question 40

brown

Answer 40

high carbon material

Question 41

green

Answer 41

high nitrogen material

Question 42

why are smaller particles in compost piles more beneficial?

Answer 42

The smaller particles have a higher surface area that promotes microbial activity and retention of moisture

Question 43

what is the ideal oxygen level in a compost pile?

Answer 43

15%

Question 44

as long as the pores in a compost pile are greater than 10%, the pile can be considered what?

Answer 44

aerobic - If the oxygen level falls below this 10%, anaerobic bacteria can really get going and produce sulfur gas, which smells like rotten egg

Question 45

what is the ideal moisture content of a compost pile to promote bacterial and fungal activity?

Answer 45

40 -60%

Question 46

what can too much moisture promote? too little?

Answer 46

- mold growth - anaerobic conditions

Question 47

improving soil quality

Answer 47

- protects the soil surface - improves soil properties - returns nutrients

Question 48

mineral soil composition

Answer 48

- organic matter - sand, silt, clay, - air - water

Question 49

organic soils composition

Answer 49

- organic matter - water - air - minerals

Question 50

composition of SOM

Answer 50

- minerals - organic matter - living and dead - pore space

Question 51

how can SOM effect the soil quality biologically?

Answer 51

- source of energy - reservoir of nutrients - soil/plant resilience

Question 52

how can SOM effect the soil quality physically?

Answer 52

Structure stability Water retention Thermal property

Question 53

how can SOM effect the soil quality chemically?

Answer 53

Cation exchange capacity Soil pH Binding ofSOM to soil minerals

Question 54

what is soil organic matter like?

Answer 54

a sponge and can supply water-holding capacity to plants

Question 55

what is the main food source for soil microbes?

Answer 55

SOM - energy stored in SOM carbon to carbon bonds

Question 56

carbon storage in the atmosphere

Answer 56

750 Pg C - stored as CO2

Question 57

carbon storage in vegetation

Answer 57

610 Pg C - stored as organic c

Question 58

carbon storage in soil

Answer 58

1580 Pg C - stored as organic c

Question 59

recycling options of organic wastes

Answer 59

- repurposed - burned - applied to soil

Question 60

controlled conditions of compost pile

Answer 60

- Carbon to nitrogen ratio - Distribution of particles sizes in the pile - Moisture content - Oxygen content - Temperature

Question 61

ideal temperatures for each composting phase

Answer 61

Phase 1: 90-130 Phase 2: 130-140 Phase 3: 60-130 Phase 4: 60

Question 62

types of composting piles

Answer 62

Static pile Windrow Bin Forced aeration windrow or pile