Calcium oxide (CaO), also known as quicklime, is commonly used for liming ponds. When water is added to CaO, it produces calcium hydroxide and releases heat. Liming with CaO increases pond pH and alkalinity, making nutrients more available to plants and fish. It can also remove carbon dioxide, kill unwanted organisms, and disinfect pond bottoms. The proper dose of liming depends on the initial pond soil pH. Liming provides several benefits but must be applied carefully as a rapid pH increase can be lethal to fish.

1. Calcium Oxide (CaO)
Presented by
Name : Pabitra Pandey
Roll no. : 12

2. Contents
• Introduction
• Chemicals used for liming
• Time for Liming in pond
• Method of Liming
• Liming dose
• Advantage
• Conclusions
• References

3. Introduction
• Application of calcium and magnesium
• Part of pond management which has several beneficial effects on the pond
and health of fish
• In acid soils, these materials react as a base and neutralize soil acidity
• It’s the most common and effective practice to reduce soil acidity

4. Basic chemicals are commonly used for liming
1. Agriculture lime
• Calcite, CaCO3
• Dolomite, CaMg(CO3)2
2. Hydrated lime or slaked limed or Builder’s lime
• Calcium hydroxide, Ca(OH)2
3. Quick lime or Burnt lime
• Calcium oxide, CaO

5. Introduction of CaO
• Lime or Quicklime or burnt lime or unslaked lime
• Odorless greyish white powder
• A white, caustic, alkaline, crystalline solid at room temperature Ionic crystal structure
of calcium
oxide(Ca2+O2-)

6. Preparation of calcium oxide
• Produced by thermal decomposition of materials that contain calcium carbonate
in a lime kiln
• Calcination; that starts with thermally decomposing the reactants at high
temperature (1070-1270)
• Held in rotary kiln; products are lime and carbon dioxide
• Carbon dioxide is immediately removed
• CaCO3 CaO + CO2

7. Introduction to slaked lime or lime water
• When water is added to lime, calcium hydroxide is formed
• CaO + H2O Ca(OH)2
• The reaction of burnt lime and water releases considerable heat
• CaO reacts faster at lower temperature than at high temperature
• Liming increases water temperature in aquaculture ponds.
• Each kilogram of CaO that react with water release 272.6 kilocalories of heat
• One kilocalorie will rise the temperature of 1L water by 1 c

8. Time of CaO applied in pond
• pH and alkalinity is too low
• Organic matter content and deposition of pond bottom mud is too high
• Threat of outbreak of contagious disease or parasites and oxygen depletion
• Prophylactic measures are needed
• Fertilization fails to produce an adequate plankton bloom

9. Methods
• Ponds should be drained and cleaned prior to applying this product
• Best applied directly to the pond bottom prior to filling the pond with water
• It should be spread evenly over the entire bottom
• A disk harrow can be used to further incorporate the lime into the soil
• Applying limestone to ponds, that are full of water is more difficult

10. Liming dose for different soil pH value
Ph value 4-5 5-6.5 6.5-7.5 7.5-8 8 or above
Amount of lime
(kg/ha/yr)
2000 1000 500 200 No need of
liming

11. Liming materials
• Important property of lime for its effectiveness is
1. particle size
• Smaller particle size are more effective in neutralizing the acidity
• Fine particles react more quickly and complete with water to rise alkalinity
2. Neutralizing value
• Refers to the relative abilities of liming materials to neutralize acidity
• It represents its capacity to neutralize acidity comparison to that of an equal
quantity of CaCO3
n𝑒𝑢𝑡𝑟𝑎𝑙𝑖𝑧𝑖𝑛𝑔 𝑣𝑎𝑙𝑢𝑒(%) = 𝑀𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐶𝑎𝐶𝑂3 /𝑀𝑜𝑙𝑒𝑐𝑢𝑎𝑙𝑟 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑙𝑖𝑚𝑖𝑛𝑔 𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙 × 100

12. Advantage of liming in pond
1. To increase the availability of nutrients
2. To increase pH and to buffer against daily pH fluctuations
3. To sterilize ponds prior to stocking
4. Improves pond soil quality by promoting mineralization
5. Precipitates excess dissolved organic matter and reduces chances of
oxygen depletion
6. Supplies calcium needed for plant growth and for bone and scales
formation in fish
7. Increases the pH of bottom mud and thereby increase the availability of
phosphorous added in water

13. Cont…
8. Shrimp ponds to regulate phytoplankton abundance and pH
9. Lime increases pH and calcium concentration favoring the removal of
phosphate from the water
10.Raising the pH also removes carbon dioxide from the water
11. Less carbon dioxide and phosphate are thought to limit phytoplankton
photosynthesis and avoid wide daily shifts in pH
12.Killing unwanted organisms including vectors of disease

14. How to increase pH
• Without lime : H2O + CO2 H2CO3 ( PH acidic )
• With lime : CaO + CO2 CaCO3
• H2O + CaCO3 Ca(HCO3)2
• CaCO3 + 2H+ Ca2+ + H2O + CO2 ( CaCO3 trap the H+ and increase
the pH)
• CaMg(CO3)2 + 4H+ Ca2+ + Mg2+ + 2H2O + 2CO2
• Ca(OH)2 + 2H+ Ca2+ +2H2O
• CaO + 2H+ Ca2+ 2H2O

15. Lime for CO2 removal
• Lime may also be applied when DO is low to remove CO2 and allowing
fish or shrimp to use the existing DO more efficiently
• Lime removes CO2 from water according to following equations:
• CaO + 2CO2 + H2O Ca2
+ + 2HCO3
-
• Ca(OH)2 + 2CO2 Ca2
+ + 2HCO3
-

16. Uses of calcium oxide
• Extensively used for medicinal purposes and insecticides.
• Manufacturing of cement, paper, and high grade steel
• As a reagent in laboratories for dehydration, precipitation reaction
• Importance ingredient in the manufacturing of caustic soda

17. Points to remember
• Soil, water, alkalinity, hardness determines the quantity of lime
• Don’t dump the lime
• If pH is near to neutral, agriculture lime will be best
• If pH is at very low level, Quicklime and hydrated lime
• Adding hydrated lime is not recommended when fish are present in the pond
• The rapid increase in ph is almost always lethal to fish

18. Conclusions
• Application of agricultural limestone to increase alkalinity to about 50 mg/l
improves production in fertilized ponds and enhances water quality in ponds for
feed-based aquaculture
• Burnt lime and hydrated lime cause an initial high pH, but they can be applied to
bottoms of empty ponds for the purpose of neutralizing bottom soil acidity
• In addition, even where acidic soil and low alkalinity are not present, burnt or
hydrated lime also may be used to raise pH and disinfect pond bottoms

19. References
• Boyd, C. E. (2017). Use of agricultural limestone and lime in
aquaculture. CABI Reviews, (2017), 1-10.
• Green, B. W. (2022). Fertilizer use in aquaculture. In Feed and
Feeding Practices in Aquaculture (pp. 29-63). Woodhead
Publishing.
• Wurts, W. A., & Masser, M. P. (2004). Liming ponds for
aquaculture. Southern Regional Aquaculture Center.
• Faruk, M. A. R., Alam, M. J., Sarker, M. M. R., & Kabir, M. B.
(2004). Status of fish disease and health management practices
in rural freshwater aquaculture of Bangladesh. Pakistan Journal
of Biological Science, 7(12), 2092-2098.