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AGRI 51 > chapter 5 a & b > Flashcards

chapter 5 a & b Flashcards

1
Q

potential of soil to supply nutrients in amounts, forms, and proportions required for the normal growth of plants

A

soil fertility

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2
Q

3 important things in soil fertility

A

content, balance, availability

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3
Q

4 factors that affect plant growth

A

genetic factors: tolerance to pest and diseases, soil acidity, elemental toxicity
environmental factors: sunlight, weather, avail of water, soil fertility, solum thickness
earth’s crust: 95% igneous, 5% sedimentary and meta
hydrosphere: 98% sea 2% fresh
atmosphere: 78% nitrogen, 20% oxygen

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4
Q

forms of available nutrients in soil

A

readily: soluble & exchangeable- fertilizers
moderately: elements in readily mineralized form- compost
difficulty: slowly decomposable sources of nutrients- fresh OM, fixed form (bodies of micro-org) P, K, NH4

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5
Q

arnon’s criteria

A
  1. deficiency of element makes it impossible for plant to complete life cycle
  2. deficiency can be corrected only by supplying limiting element
  3. element must be directly involved in nutrition of plant
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6
Q

absorbed by plants in large amount

A

macro nutrients

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7
Q

absorbed by plants in small amount

A

micro nutrients

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8
Q

non-mineral nutrients

A

hydrogen, carbon, oxygen

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9
Q

macro nutrients

A

primary: N, P, K
secondary: Ca, Mg, S

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10
Q

micro nutrients

A

boron, copper, iron, chloride, manganese, molybdenum, zinc

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11
Q

nitrogen is essential component of plant material especially

A

protein molecule

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12
Q

when N is deficient

A

root system and plant growth is stunted
older leaves turn yellow
crop is low in crude protein

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13
Q

too much N

A

delay maturity
excessive growth

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14
Q

N fertilizer is produced by

A

haber-bosch process

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15
Q

gradual increase of P, N, and other plant nutrients in an aquatic ecosystem

A

eutrophication

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16
Q

process that increase N content

A

fixation
mineralization: nitrification, ammonification

17
Q

process that decrease N content

A

denitrification
volatilization
immobilization
leaching

18
Q

in what form of N is taken by plant

A

nitrate (NO3-)

19
Q

conversion of atmospheric N to plant available form

A

fixation

20
Q

biological process of N fixation

A

biological N-fixation by legume crops and microorganisms

21
Q

nitrogen fixation requires

A

energy, enzymes, and minerals

22
Q

microorganism fixing N2

A

cyanobacteria
green sulfur bacteria
azotobacteraceae
rhizobia
frankia

23
Q

microbes decompose organic N from manure
OM and crop residues to ammonium

A

mineralization

24
Q

rate of mineralization vary with

A

soil temp
moisture
aeration (amount of oxygen)

25
Q

mineralization readily occurs in

A

warm well-aerated and moist soils

26
Q

process of degradation f organic nitrogenous constituents of freshly added residues as well as those in SOM, which produces ammonia

A

ammonification

27
Q

under aerobic condition, ammonia produced is

A

rapidly converted to nitrate by bacteria

28
Q

under anaerobic condition, such as paddy paddy fields

A

mineralization favors the accumulation of NH4-

29
Q

microorganism convert ammonium to nitrate to obtain energy

A

nitrification

30
Q

2 groups of bacteria in nitrification

A

nitrosomonas
nitrobacter

31
Q

N is lost through conversion of nitrate to gaseous forms of N, such as nitric oxide, nitrous oxide, and nitrogen gas

A

denitrification

32
Q

denitrification is common

A

poorly drained soils

33
Q

soil is saturated and bacteria use nitrate as oxygen source

A

denitrification

34
Q

loss of N through conversion of ammonium to ammonia gas, which is released to atmosphere

A

volatilization

35
Q

volatilization losses increase at

A

higher soil pH and conditions that favor evaporation (hot and windy)

36
Q

volatilization losses are higher for

A

manures and fertilizers that ae surface applied and not incorporated (by tillage or rain) into the soil

37
Q

reverse of mobilization
nitrate and ammonium are taken up by soil organism and becomes unavailable to crops

A

immobilization

38
Q

rate of leaching depends on

A

soil drainage
rainfall
amount of nitrate present in soil
crop uptake

AGRI 51 (11 decks)

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