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Soil Science > Mid term test > Flashcards

Mid term test Flashcards

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1
Q

Climatic factors affecting yield

A 
Precipitation (quantity & distribution)
Air temperature 
Relative humidity 
Light
wind
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2
Q

Soil factors affecting yield

A 
Organic matter 
Texture
Structure 
Soil fertility
Slope and topography 
Soil temperature 
Soil moisture 
Tillage
Depth
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3
Q

Crop factors affecting yield

A 
Crop species
Variety
Planting date
Seeding rate
Seeding quality
Pest
Row spacing
Evapotranspiration
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4
Q

The law of the minimum

A

Crop yield is determined by the most limiting factor. Yield can only increase if the limiting factor is eliminated .

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5
Q

Sources of mineral nutrients for plant uptake

A

Uptake from the soil solution.

The amounts of nutrients in the soil solution are small.

Alone these nutrients are not enough to produce a good crop.

Nutrients are replenished by those in soil solid phase

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6
Q

Nutrient supply is affected by

A

The nutrient concentration in soil solution

Amount of nutrient adsorbed on soil surfaces

The nutrient buffering capacity

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7
Q

What is buffering capacity

A

the ability of a soil to resist charge

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8
Q

Buffering capacity

A

The buffer capacity (BC) is described by the change in the amount of ion adsorbed (change in Q) as a result of a change in solution concentration (change in I)

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9
Q

How to increase buffering capacity

A

Increases with CEC, organic matter, and clay content

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10
Q

How does clay content increase buffering capacity

A

Higher clay content has higher CEC, clay has fine particles so larger surface area

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11
Q

Movement of ions from soil to roots - Root interception

A

Root growth increases soil-root contact

Directly taken up by plants

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12
Q

Movement of ions from soil to roots - Mass flow

A

Mass water flow

Provides large amounts of Ca2+, Mg2+, NO3 - , Cl- and SO4 2-

Decreases with lower soil moisture content and temperatures

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13
Q

Movement of ions from soil to roots - Diffusion

A

Ion moves from areas of high concentration to low concentration

Concentration gradient is created by plants absorbing nutrients

Rate reduces at lower soil moisture content

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14
Q

Soil Testing

A

Soil test is a chemical method for estimating the nutrient-supplying power of a soil.

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15
Q

What to avoid when soil sampling

A
  • sampling atypical areas or after fertiliser additions
  • e.g. close to fence lines, animal tracks, camping ground
  • within six months of liming, immediately after grazing
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16
Q

Depth of soil sampling

A

75mm for pastures

150mm for arable land with cultivation

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17
Q

Soil sampling frequency

A

every 3-4 years for monitoring

more frequently during fertility development phase

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18
Q

what is Olsen P

A

Measures plant available P in soil solution and some in solid phase.

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19
Q

How is olsen p extracted

A

with sodium bicarbonate NaHCO3 ) (pH 8.5) solution.

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20
Q

Sulfate sulfur test

A

Extracting with potassium phosphate (KH2PO4 ) solution

Measures soil solution sulphate and exchangeable sulphate on soil surfaces

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21
Q

Why is it difficult to test Nitrogen in the soil

A

Because most N is in organic form

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22
Q

How is N in organic matter released?

A

via mineralization process

23
Q

What is the sulphur leaching index determined by

A
  • sulphate retention of soil
  • annual rainfall
  • drainage status of soil
24
Q

What does plant analysis aid in?

A
  • identify deficiency symptoms
  • help determine soil nutrient status
  • help determine the efffect of fertilisation
  • help study relationship between plant nutrient concentration and crop yield
25
Q

Total plant analysis

A
  • performed on the whole plant or plant parts for total elemental concentrations
  • relative plant yield vs nutrient concentration in plant
26
Q

Tissue tests

A

Nutrient concentration in tissue sap is a good indication of nutrient supply - latest mature leaf

27
Q

Chlorophyll meters for plant N status

A

A hand-held chlorophyll meter is used to indicate leaf N status

28
Q

NPKS - (NH4 )2SO4 Ammonium Sulphate

A

21-0-0-24

29
Q

NPKS - (NH2 )2 CO Urea

A

46-0-0-0

30
Q

NPKS - CaNH4NO3 Calcium Ammonium Nitrate

A

27-0-0-0

31
Q

NPKS - Single superphosphate

A

0-9-0-12

32
Q

NPKS - Nitrogen super

A

6-6-0-15

33
Q

Triple superphosphate

A

0-20-0-2

34
Q

NPKS - DAP

A

18-20-0-2

35
Q

NPKS Calcium sulphate

A

0-0-0-20

36
Q

Cost/kg of nutrient

A

Cost/tonne fertiliser divided by (10x % nutrient in fertiliser)

  • eg Urea (46-0-0-0) $620 / tonne
  • 620 / (10 x 46) = $1.35 /kg
37
Q

Fertiliser rate equation

A

(100 x nutrient required (kg/ha) / % nutrient in fert

  • 22kg P/ha, how much super phosphate 0-9-0-1
  • (100 x 22) / 9
  • = 244 kg
38
Q

Sulphur nutrient cycle

A

refer to notes

39
Q

Nitrogen cycle

A

refer to notes

40
Q

Phosphorus cycle

A

refer to notes

41
Q

Potassium cycle

A

refer to notes

42
Q

RPRs vs Superphosphate

A
  • RPRs are cheaper
  • RPRs have little to no S
  • RPRs are slower release
  • RPRs only effective under high rainfall, and low soil pH
43
Q

Elemental S breakdown process

A
  • Must be oxidised by specialised soil bacteria into sulphate before the plant can use it
  • 2S + 302 + 2H20 -> 2H2S04

S04 is plant available

44
Q

How is SSP made

A

Made by reacting insoluble rock phosphate with sulphuric Acid (H2SO4 )

This process converts insoluble phosphates into forms more readily available to plants

45
Q

How to choose a fert

A
  1. Nutrients it contains
  2. concentration of nutrient
  3. form of nutrient
  4. rate nutrient becomes available to plants
  5. cost /kg of nutrient
  6. risk of damage to sensitive plants
46
Q

Efficient use of fertilisers

A
  1. reduce costs of production
  2. avoid wastage of non-renewable resources
  3. avoid pollution of groundwater and environment
  4. improve the efficiency of production
47
Q

When to apply fertilisers

A
  1. during periods of rapid plant growth
  2. in cropping, lime or phosphate fertiliser usually done during soil cultivation
  3. do not apply lime and superphosphate together
48
Q

How is N fert made

A

Haber-bosch process - combines N with hydrogen under pressure making liquid nitrogen.

49
Q

pH buffering capacity

A

The ability of soil to resist pH change

50
Q

In what soils can plants tolerate more acidity?

A

Organic soils

For most plants = optimum around pH 6

51
Q

Benefits of applying lime

A
  1. Decreases Al toxicity
  2. Increases P availibility to plants
  3. Increases mineralisation rate
  4. increases N fixation
  5. improves soil structure
  6. Decrease toxic effects of some micro nutrients
52
Q

The depletive phase of soil fertility

A

Cultivation stimulates mineralization of organic matter

  • degrades structure
  • Reduces biological activity
  • depleats fertility
53
Q

The restorative phase of soil fertility

A

in pasture phase

  • Legumes
  • organic matter built up by pasture resides, roots, animal poo, which improves the structure
  • Biological activity increases
  • soil fertility increase

Soil Science (1 decks)

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