chapter 5 a & b

Question 1

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

Answer 1

soil fertility

Question 2

3 important things in soil fertility

Answer 2

content, balance, availability

Question 3

4 factors that affect plant growth

Answer 3

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

Question 4

forms of available nutrients in soil

Answer 4

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

Question 5

arnon’s criteria

Answer 5

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

Question 6

absorbed by plants in large amount

Answer 6

macro nutrients

Question 7

absorbed by plants in small amount

Answer 7

micro nutrients

Question 8

non-mineral nutrients

Answer 8

hydrogen, carbon, oxygen

Question 9

macro nutrients

Answer 9

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

Question 10

micro nutrients

Answer 10

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

Question 11

nitrogen is essential component of plant material especially

Answer 11

protein molecule

Question 12

when N is deficient

Answer 12

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

Question 13

too much N

Answer 13

delay maturity
excessive growth

Question 14

N fertilizer is produced by

Answer 14

haber-bosch process

Question 15

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

Answer 15

eutrophication

Question 16

process that increase N content

Answer 16

fixation
mineralization: nitrification, ammonification

Question 17

process that decrease N content

Answer 17

denitrification
volatilization
immobilization
leaching

Question 18

in what form of N is taken by plant

Answer 18

nitrate (NO3-)

Question 19

conversion of atmospheric N to plant available form

Answer 19

fixation

Question 20

biological process of N fixation

Answer 20

biological N-fixation by legume crops and microorganisms

Question 21

nitrogen fixation requires

Answer 21

energy, enzymes, and minerals

Question 22

microorganism fixing N2

Answer 22

cyanobacteria
green sulfur bacteria
azotobacteraceae
rhizobia
frankia

Question 23

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

Answer 23

mineralization

Question 24

rate of mineralization vary with

Answer 24

soil temp
moisture
aeration (amount of oxygen)

Question 25

mineralization readily occurs in

Answer 25

warm well-aerated and moist soils

Question 26

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

Answer 26

ammonification

Question 27

under aerobic condition, ammonia produced is

Answer 27

rapidly converted to nitrate by bacteria

Question 28

under anaerobic condition, such as paddy paddy fields

Answer 28

mineralization favors the accumulation of NH4-

Question 29

microorganism convert ammonium to nitrate to obtain energy

Answer 29

nitrification

Question 30

2 groups of bacteria in nitrification

Answer 30

nitrosomonas nitrobacter

Question 31

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

Answer 31

denitrification

Question 32

denitrification is common

Answer 32

poorly drained soils

Question 33

soil is saturated and bacteria use nitrate as oxygen source

Answer 33

denitrification

Question 34

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

Answer 34

volatilization

Question 35

volatilization losses increase at

Answer 35

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

Question 36

volatilization losses are higher for

Answer 36

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

Question 37

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

Answer 37

immobilization

Question 38

rate of leaching depends on

Answer 38

soil drainage rainfall amount of nitrate present in soil crop uptake