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Agriculture Quality > Module 7: Nitrogen and Phosphorous Cycles > Flashcards

Module 7: Nitrogen and Phosphorous Cycles Flashcards

1
Q

plant nutrients

A

nitrogen, phosphorous, magnesium, calcium, and a few other elemtnts

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2
Q

how can we determine plant growth in any land-based ecosystem?

A
  • optimal temperature
  • moisture
  • light condition
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3
Q

what is distribution of a crop based on?

A
  • optimal temp
  • light
  • soil conditions
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4
Q

what impacts management practices?

A

soil properties and climate
- igher
quality soil means fewer inputs are required to grow crops. Hence, lower quality soils require
more water, more nutrients to maintain a viable crop yield

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5
Q

how much nitrogen is in the atmosphere?

A

78%

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6
Q

what forms of nitrogen can plants assimilate?

A
  • nitrates
  • nitrites
  • ammonium
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7
Q

legumes

A

soybeans, clover, peanuts, kudzu

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8
Q

nitrogen fixing bacteria

A
  • convert atmospheric nitrogen into ammonia
  • do this through an enzyme called nitrogenase which is the only biological enzyme that can break the nitrogen triple bond
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9
Q

how else can ammonium be made?

A
  • other decomposers like fungi, protists, and other kinds of bacteria
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10
Q

nitrifying bacteria

A
  • can take ammonia from the nitrogen fixing bacteria and turn into nitrates and nitrites
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11
Q

denitrifying bacteria

A

metabolize nitrogen dioxide and turn back into nitrogen has using a special enzyme called nitrate reductase

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12
Q

what is unique about the phosphorous cycle?

A
  • only element that does not involve the atmosphere
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13
Q

phosphorous cycle

A
  • re-exposed rocks with water eroding them and phosphates are dissolved into water
  • immediately available to plants
  • decomposers can break down living things and integrate phosphorous back into the soil or water
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14
Q

what are the three categories of fluxes?

A

additions, losses, and internal transformations
- key to determining nutrient availability in any ecosystems

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15
Q

nutrient additions

A

through atmospheric deposition, nitrogen fixation, and mineral weathering of rocks in phosphorous minerals
- very low and not enough to support plant annual growth requirements

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16
Q

how are plant nutrient needs met?

A

decomposition and mineralization
- internal transformation

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17
Q

additions in target ecosystem

A
  • atmospheric deposition through rain or dust
  • weathering of rocks or minerals
  • biological nitrogen fixation
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18
Q

losses in target ecosystem

A
  • leaching of nutrients with water
  • gaseous losses to the atmosphere
  • erosion of soil by wind or water
19
Q

transformations in target ecosystem

A
  • keep nutrients stored
  • still active and still available for plant and microbial growth
20
Q

what is an important distinction between the phosphorous and nitrogen cycle?

A

almost all the fluxes within the nitrogen cycle are mediated by microbes
- the phosphorous cycle is mediated by mineralization and immobilization

21
Q

mineralization

A

the conversion of organic nitrogen and phosphorus to inorganic
nitrogen and phosphorus that are soluble in water and available for plant and microbial uptake

22
Q

nitrification

A

only takes place in the presence of oxygen and results in the production of nitrate

23
Q

how can microbes gain energy?

A

from converting ammonium to nitrate

24
Q

mobilization

A
  • reverse of mineralization
25
Q

denitrification

A

only takes place in the absence of oxygen and
is how we get nitrogen back from the soil and the atmosphere

26
Q

how long does it take to form 38 cm of rock?

A

20,000 years

27
Q

how is nitrogen primarily lost?

A

nitrate leaching and denitrification

28
Q

how is phosphorous primarily lost?

A

erosion

29
Q

what are some similarities between the nitrogen and phosphorous cycles?

A
  • stored in soil, water, and living biomass
  • movement through mobilization and mineralization
30
Q

why does phosphorous readily fixed in the soil?

A

by adsorption and precipitation processes

31
Q

what is phosphorous sorption and precipitation high dependent on?

A

pH
- very soluble at neutral pH

32
Q

acidic soils

A

high in aluminum or iron
- phosphate readily sticks or absorbs to the surface or locked to the actual soil particles

33
Q

basic soils

A
  • more calcium
  • calcium and phosphate in the soil solution immediate form calcium phosphate forming a precipitate
34
Q

what is the pH of most agricultural soils?

A

a little above or a little below neutral

35
Q

nitrogen mineralization

A

the conversion of organic nitrogen into
ammonium, an inorganic form of nitrogen that is soluble in water. Since ammonium is soluble in
water, we consider it to be part of the soil solution

36
Q

what are the 5 factors that impact plant growth?

A

Climate
Soil properties
Management
Plant age
Plant genetics
Irrigation schedule
Nitrogen nutrient management

37
Q

nutrient cycles: pools

A
  • plant (living) biomass
  • soil
  • minerals
  • water bodies
  • atmosphere
38
Q

comparisons of natural and conventional agricultural ecosystem

A
  • natural ecosystems: additions are small, losses are small, Internal transformations provide a plant’s daily nutrient needs
  • agricultural ecosystem: additions are greater, losses are greater, Internal transformations cannot meet a crop’s daily nutrient needs without the additions of fertilizers
39
Q

what is the key to understanding nutrient cycles is to identify what factors?

A
  • pools
  • fluxes
  • ecosystem boundaries
40
Q

differences in inputs of N and P

A
  • P - born of rock (weathering, dust)
  • N - born of air
41
Q

differences in transformations of N and P

A
  • N - microbially mediated
  • N - involves transfer of energy
  • P - involves P minerals
42
Q

differences in losses of N and P

A
  • N - losses by leaching and gas production
  • P - losses by erosion
43
Q

similarities between N and P

A
  • immobilization and mineralization
  • connected the carbon cycle via decomposition and soil organic matter formation
44
Q

best management practices promote

A
  • Right amount of fertilizer to minimize overloading
  • Conditions that promote organic matter, which promote immobilization of N and P
  • Conditions that minimize erosion and leaching losses

Agriculture Quality (18 decks)

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