Problem Soils Flashcards
Types of problem soils
- Acid soils
- Calcareous soils
- Salt affected soil
one of the most important soil
fertility problems in the tropics
Acid soils
Soils become acidic when considerable portions of
the exchangeable cations are
hydrogen (H+) and
Al3+
acidic cations-
Fe, Al, H
basic cations-
Ca, Mg, Na, K
produced from soil organic matter
decomposition
Organic acids
Strong acids?
c. carboxylic acid
d. phenolic acid
organic matter forms Soluble complexes with
non-acid nutrient cations (Ca & Mg) thus,
facilitating the loss of these cations by_____.
Leaching
removal
of H+ ions from
functional group of
organic matter.
Deprotonation
rain water or irrigation water that moves
downward through the soil dissolves nutrients
and move with water
Leaching
soils that developed from_____
are likely to be more acidic than those
developed from shale or limestone
Weathered granite
H+ and Al3+ in the soil solution
Active acidity
portion of H+ and Al3+ ions
that are adsorbed by soil colloids (e.g., clay and
organic matter) that can be replaced by salt
solution such as KCl or NaCl.
Exchangeable acidity
refers to bound H+ and Al3+ ions
that cannot be replaced by salt solution.
Residual acidity
sulfur oxidation in acid sulfate
soil
Potential acidity-
can form soluble complexes with
Al ions that are non-toxic to plants and microbes.
organic acids
contains oxides of Ca, Mg and K)
Wood ashes
Managing acid soil
- Using organic matter
- Wood ashes (contains oxides of Ca, Mg and K)
- Biochar
A Soil with high calcium carbonate (CaCO3)
content and give effervescence visibly releasing
CO2 gas treated with hydrochloric acid (HCl)
Calcareous soils
• CaCO3 content ranged from___%to___%
by weight
3% to more than 25%
pH value of Calcareous soils
7.6-8.3
Why calcareous soils have
alkaline pH
Dissolution of CaCo3 in water produces OH- which
raises soil pH
• Formed largely by the weathering of parent
material rich in CaCO3 such limestone, chalk, marl
calcareous soils
Commonly found in arid and semi-arid region
(evapotranspiration>precipitation)
calcareous soils
True or false
• Application of acid forming fertilizers such as
ammonium sulfate and urea fertilizers can manage calcareous soils
True
Problems associated with
calcareous soils
- Crust formation
- Ammonia volatilization
- Precipitation of soluble phosphate
- Precipitation of iron compounds
• White alkali salts
• Salty white crusts on the soil surface due to
accumulation and precipitation of CaSO4, CaCO3
and MgCO3,
CaCl2 , MgSO4, MgCl2,
NaC
Saline soils
pH of saline soils
pH < 8.5
Effect on plant growth?
ELECTRICAL CONDUCTIVITY: 8.1 to 16 , Strongly saline
Most cultivated plants are
inhibited
1 mmhos/cm=?
100 S/m
1 Siemens/cm= ?
1 mmhos/cm
Is <640 ppm salt suitable for crops?
Uu hehe
TRUE OR FALSE
>1,600 ppm salt is suitable for crops
false
How do salts accumulate in soils?
- Weathering of primary
minerals - High evaporation, low
precipitation - Irrigation water containing high levels of salts
- Application of fertilizers, amendments and
manure containing high salts
The following are effects of saline
soils on plant. EXCEPT
- Wilting
- Root injury
- Poor germination
4.Leaf burn
5. Stunted growth
6. Death
7. None of the above
- None of the above
• Black alkali soils
• EC < 4 dSm-1
• Exchangeable Na (>15 %)
Sodic soils
Ph of sodic soils
pH at or above 8.5
True or false
Sodic soils are dispersed soil condition
True
- Dispersion of soil colloids leads to development
of compact soils. true or false?
True
White crust on the surface formed from dispersed
organic matter is a symptoms of sodic soil. True or false
False- BLACK CRUST
Soil particles will disperse if
concentrations of (Ca2+ + Mg+) are
INCREASED relative to the
concentration o f Na* (SAR i s
increased). T or F?
False- DECREASED
• EC > 4 dSm-1
• Exchangeable Na is greater than 15 %
• pH less than 8.5
• Contains large amount of total soluble salts
• Good soil physical properties as long as an excess
of soluble salts is present
Saline-sodic soils
Saline sodic pH?
pH less than 8.5
. Applying irrigation (flooding) approximately 1 foot
high can reclaim saline soils
T or f?
T
• 6 inches or 15.24 cm can remove___% of salt within
the topsoil (1,524,000 million L ha-1)
50%
12 inches or 30.48 cm can remove__ % of salt within
the topsoil (3,048,000 million L ha-1)
80%
24 inches or 60.96 cm can remove70 % of salt within
the topsoil (6,096,000 million L ha-1)
T or f
F - 90%
Ngano deman ko niya ge pursue
Its because i dasurv betterrrr😝😝😝🫵🫵🫵🫵
Symptoms:
1. Wilting
2. Root injury
3. Poor germination
4. Leaf burn
5. Stunted growth
6. Death
The following symptoms above are the effects of ___ soils on plants
a. Sodic soil
B. Saline-sodic soils
C. Calcareous soils
D. Saline soils
D. Saline soils
