Lecture 4

Question 1

contour plowing

Answer 1

follows contour of land to minimise soil degradation

Question 2

agro-forestry (trees on edge of crop lands) use of trees

Answer 2

to recycle nutrients and water deep in soils - below the rooting depth of annuals crops

Question 3

problems from focussing on growing just a small diversity (or one) species of crop

Answer 3

= global food security threat

• outbreak of pest / disease
• the irish potato famine 1845 - 1849
• over 1,500,500 dies of starvations

Question 4

increasing the diversity of crops may:

Answer 4

• reduce pest & disease pressures,
• increase nutrient-use efficient
• reduce risks of large-scale crop failures
• improve soil quality
• may improve food security especially in relation to increasing threats from CC and pests and diseases resistance to chemical control

Question 5

soil provides plants with

Answer 5

• support
• nutrients
• water
• oxygen requirement of roots (except wetland plants)
• protection of underground buds from temp. extremes

Question 6

soil can be hostile environment:

Answer 6

• pathogens
• root grazers
• toxins
• too much or too little water
• inadequate aeration

Question 7

soil: a 3-phase system

Answer 7

• solid (mineral, organic)
• liquid (free water, structural/unavailble water)
• gas (air): (enriched in CO2, depleted in O2)

Question 8

approximately half go the volume of soil is

Answer 8

pore space containing water/ air

Question 9

most UK soils now have less than _% organic matter

Answer 9

2%

-provides most of energy to plants

Question 10

soil air is _____ from atmosphere and varies with

Answer 10

distinct and varies with depth

-e.g. CO2, CH4 increases as you go down , O2 decreases

Question 11

why are soils tilled?

Answer 11

• prepare a fine loose soil layer for seedlings to establish
• bury weeds, crop residues and pathogens
• release nutrients
• reduce surface & subsurface compaction

-ISSUE: Long term effects of tillages on soil sustainability and soil erosion

Question 12

types of tillage

Answer 12

• • different types mean different times the soil is driven over, disturbed and left bare
• conventional
• minimum tillage
• zero tillage

Question 13

conventional tillage:

Answer 13

1) inversion tillage
2/3) disking /power harrow
3/4) seed (Drill)

Question 14

minimum tillage:

Answer 14

1) shallow disc cultivation
2) drill (And chemical weed kill)
- leaves behind partial crop residue
- depended on herbicide

Question 15

zero tillage (direct drill):

Answer 15

1) slot drill (and chemical weed kill)
- almost complete cover by crop residue
- depended on herbicide
- tractor tyres = wide, low pressure to reduce compactor

Question 16

power harrow:

Answer 16

breaks down big clumps to smaller

-if soil dry, loss of substance to wind

Question 17

consequence of machinery driving on fields

Answer 17

• compact soils leads to compact traffic pan under ‘plow’ layer soil
• effects root penetration

Question 18

uptake of lesser tillage in canada?

Answer 18

rapid uptake, helps reduce soil erosion

Question 19

uptake of lesser tillage in north america?

Answer 19

adopted minimum tillage and no-tillage but erosion rates remain unsustainable

Question 20

uptake of lesser tillage in UK?

Answer 20

lagging behind, 60% conventional, 32% reduced, 8% zero

Question 21

reduced tillage potential savings of __% energy use per

Answer 21

26%

less fuel required!!

Question 22

conventional tillage causes loss of

Answer 22

• organic matter
• nutrients
• water storage
• increases soil erosion
• earthworn populations
• interrupts fungal interactions

Question 23

soil properties: Texture

Answer 23

based on particle size distribution of mineral fragments in soil

• Gravel >2mm
• coarse sand 0.2-2mm
• fine sand 0.02-0.2mm
• silt 0.002-0.02mm
• clay <0.002mm

Sand soil = drain quick, store little water good aeration
clay = oposite
loam soil = mixture –> good for most plants

Question 24

soil texture changes

Answer 24

very stable, only changes slowly due to weathering

Question 25

soil structure controls

Answer 25

the passage of water and oxygen into the soil and affects nutrient-holding capacity

• structure can overcome some of the limitations by texture
• -clay -increase creation and drainage
• -sand - improve water and nutrient holding

Question 26

how does tillage affect structure?

Answer 26

more than half of larger aggregates are lost

• so larger pore spaces are not generated
• less able to hold water

Question 27

loss of soil organic matter as a result of cultivation has compromised soil functioning:

Answer 27

nutrient and water-holding capacity - limiting crop yields and increasing vulnerabilities to water logging and drought

Question 28

how does tillage affect pores?

Answer 28

lose larger pores when you till

–results in loss of clays and OM – cycle

Question 29

7 major factors of ped formation

Answer 29

• colloidal fraction (clay&humus)
• cementing agencies
• expansion and contraction by wetting and drying
• plant roots
• micro-organisms
• micro and meso fauna (earthworms, grazing animals)
• cultivation and drainage

Question 30

macroaggrogate formation:

Answer 30

• fine roots, especially grasses
• mychorrhizal fungi and other fungi
• earthworms and other soil animals

Question 31

earthworms: ploughing and harrowing

Answer 31

• ploughing brings them to surface, predation by seagulls

- harrowing chops them up

Question 32

ploughing on mychorrhizal

Answer 32

breaks them up

Question 33

once lost? how long does it take to restore macroaggrogates?

Answer 33

-10 years of pasture and still no where near virgin soil values

Question 34

macroaggregates and soil organic carbon may be restores by

Answer 34

stopping cultivation and use of grass (lets)

Question 35

loss of organic matter leads to loss of

Answer 35

water storage capacity, soil compaction