Soil Fertility and Nutrient management (1+1)

Management or Amelioration of soil acidity

• In general the fertility status of acid soils is very poor and under strongly to moderately acidic soils, the plant growth and development is affected to a great extent. The crops grown on such problematic soils do not give remunerative returns. One of the most important and practically feasible management practices is the use of LIME AND LIMING MATERIALS to ameliorate the soil acidity.
• The addition of lime raises the soil pH, thereby eliminating most major problems of acid soils. Cultivation of acid tolerant crops/varieties is also possible option.

Lime requirement (LR): Is defined as the amount of liming material that must be added to raise the pH to some desired value (pH 6.0 to 7.0). There are a number of liming materials available in the market and may be used according to their availability, convenience and economy. Some of the important liming materials are;
1. Lime oxide (CaO)- Burnt lime/quick lime or oxide of lime. Caustic in nature and difficult to handle.
2. Lime hydroxide {Ca (OH)2}- hydrated lime or slaked lime. Caustic in nature and difficult to handle.
3. Lime carbonate (CaCO3)- ground lime stone occurs as Boglime or marl, Calcite, Oysters shells and precipitate carbonates. It is most commonly used and it is largely sold in the market as pulverized or ground lime stone, called agriculture lime.
4. Basic slag: Byproduct of Iron industry.
5. Dolomite (CaMgCO3)

Liming reaction in soils
          H+ [Soil] + CaCO3 ------- Ca2+ [Soil) + CO2 + H2O
                                                      or
                       CaCO3+H2CO3 -------Ca (HCO3)2
            H+ [Soil] + Ca(HCO3)2-------- [Soil ]Ca2+ + 2 H2O + 2CO2

Benefits of liming on acidic soils
1. Direct benefits
a. Addition of lime raises the soil pH to a desired level.
b. It eliminates major problems of Fe, Al, Mn and H toxicities.
2. Indirect benefits
a. The nutrients like Ca2+ and Mg2+ are added to the soil if lime is dolomite (Ca, MgCO3)
b. The raised pH also reduces excess soluble Mn and Fe by forming insoluble hydroxides.
3. Phosphorus availability is improved or increased because of liming precipitates Fe and Al in other forms (P is fixed as Fe and AlPO4).
4. It makes K+ more efficient in plant nutrition.
5. It increases the availability of N by creating a more favorable environment for microbes.
6. Bacterial activity is enhanced and help in control of certain plant pathogens like club rot disease of cole crops. 
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