chapter 4c

Question 1

more H+ ions

Answer 1

pH low (acidic)

Question 2

more OH+ ions

Answer 2

pH high (alkalinity)

Question 3

negative logarithm of the total hydrogen ion concentration in the solution

Answer 3

pH

Question 4

acidity or alkalinity, due to relative concentration of H+ and OH ions

Answer 4

pH

Question 5

humid
arid
inorganic

Answer 5

5 to 7
7 to 9
4 to 10

Question 6

relationship between pH and %BS

Answer 6

linear relationship

Question 7

as pH increases

Answer 7

H+ decreases

Question 8

method by pH meter, more accurate

Answer 8

electrometric method

Question 9

organic dyes, litmus paper (ex: cornell pH)

Answer 9

colorimetric method

Question 10

soil test kit

Answer 10

nitrogen, phosphorus, and potassium. next is lime requirement

Question 11

effects of soil pH on microbial act

Answer 11

fungi: unaffected
bacteria & actinomycetes: inhibited at pH 5

Question 12

(1) origin of soil acidity

Answer 12

release of hydrogen atoms under natural chemical processes in the soil

Question 13

rel of H under natural chem

Answer 13

*atmospheric carbon dioxide reacts w/ water to form carbonic acid
*organic molecules reacts w/ water and causes acid dissociation
*oxidation of ammonium nitrogen, sulfur, and iron

Question 14

(2) origins of soil acidity

Answer 14

accumulation of OM and subsequent release of products of decomposition: fulvic and humic acid

Question 15

(3) origins of soil acidity

Answer 15

reaction of aluminum cations with water, “hydrolysis”

Question 16

(4) origins of soil acidity

Answer 16

natural deposition
- lightning deposits nitric acid
- volcanic activity deposits sulfuric acid
- mineral weathering: Pyrite or Fool’s Gold (FeS2) once oxidized, results to formation of acid sulfate soils

Question 17

(5) origins of soil acidity

Answer 17

human factors
- oxidation of applied synthetic ammonium-based fertilizer
-oxidation of nitrogen compounds in applied animal manure or sewage
- deposition of acid rain (nitric and sulfuric caused by industrialization)

Question 18

forms of soil acidity

Answer 18

active acidity: due to H+ in soil solution, determined as pH
reserve acidity: due to H+ and Al+++ in the solid phase

Question 19

ability of soil to resist sudden/drastic changes in pH

Answer 19

buffering capacity

Question 20

measure of the buffering capacity of soil

Answer 20

reserve and active acidity

Question 21

buffering capacity is high if

Answer 21

CEC is high
clay content is high
OM content is high

Question 22

production constraints associated with acid soils

Answer 22

aluminum toxicity- usually damages the root system first
mn toxicity- less common than Al toxicity
nutrient deficiency- P, Ca, and Mo deficiency (also nitrogen)

Question 23

(4-5) production constraints with acid soils

Answer 23

restricted microbial activities: mineralization of organic N, biological fixation of N
incidence of plant diseases: some plants are more likely to be affected by damping off (fungal disease) and root rot in acid soils

Question 24

(1) management strategy

Answer 24

reduce acidification
- minimize use of acidifying fertilizer
- reduce leaching of N by use of split applications of fertilizer
- return plant material to soil

Question 25

(2) management strategy

Answer 25

used acid-tolerant crops - sweet potato, coffee, radish, tomato, pineapple, strawberry, irish potato

Question 26

(3-4) management strategy

Answer 26

apply more nutrients apply agricultural lime

Question 27

only means of correcting soil acidity

Answer 27

lime

Question 28

any oxide, hydroxide, or carbonate of Ca or Mg used to neutralize soil acidity

Answer 28

lime

Question 29

carbonate form

Answer 29

CaCo3 (calcitic limestone) CaMg(Co3)2 dolomitic limestone

Question 30

oxide and hydroxide form

Answer 30

CaO (burned lime) Ca(OH)2 hydrated lime

Question 31

depends on soil

Answer 31

pH: lower- more lime exchangeable Al- more, more lime texture- clayey, more lime OM- depeds

Question 31

amount of lime depends on soil

Answer 31

pH: lower- more lime exchangeable Al- more, more lime texture- clayey, more lime OM- depends

Question 32

amount of lime depends on (2)

Answer 32

type and variety of crops to be grown

Question 33

amount of lime depends on (3)

Answer 33

kind of lime - fineness - chemical guarantee

Question 34

amount of lime depends on (4)

Answer 34

economic return from lime application

Question 35

amount of salt that have accumulated in the soil

Answer 35

salinity

Question 36

expressions of chemical guarantee of lime

Answer 36

oxide content in %CaO r %MgO calcium oxide equivalent- strength in pure CaO calcium carbonate equivalent (neutralizing power)- CaCo3

Question 37

high osmotic potential

Answer 37

low salt concentration

Question 38

low osmotic potential

Answer 38

high salt concentration

Question 39

excess Na causes

Answer 39

disperse and swell, affect drainage, aeration, and root penetration. toxicity to plants

Question 40

ability of substance to conduct electric current

Answer 40

electrical conductivity

Question 41

ability of an electrolytic solution to conduct electric current

Answer 41

electrical conductivity

Question 42

index of total ionic concentration in solution

Answer 42

electrical conductivity

Question 43

more saline

Answer 43

higher EC

Question 44

correct salinity

Answer 44

irrigation water

Question 45

correct sodicity

Answer 45

gypsum or sulfur