CAUSES OF SOIL ACIDITY
. Soil acidity is caused when heavy rains leach bases like Ca2+, Mg2+, K+ and Na+ from the soil to the ground water table leave surplus H+ in the soil.
. Also industrial regions may bring sulphuric (vi) acid and nitric (v) acid to the soil which increases its acidity.
. Acidic mineral fertilizers like ammonium sulphate (vi) and ammonium chloride make the soil more acidic due to hydrolysis.
. Also the nitrification of ammonium ions by bacteria produces H+(aq)
NOTE: Organic acids are produced during the decomposition of organic matter. Due to this, most soils in humid tropics are Acidic.
Liming & liming materials
Discuss:
– Meaning and significance of liming as treatment to soil PH.
– The efficiency of liming materials i.e. neutralizing values of carbonates, oxides, hydroxides and silicates.
– Beneficial effects of liming
– Detrimental effects of over-liming
Liming:
It refers to the process of adding basic compounds of calcium and magnesium to acid soil (PH 
5) in order to raise the PH of the soil to the required level.
The compound of calcium and magnesium (oxides, hydroxides, carbonates and silicates) are called agricultural limes. Such compounds are contained in limestone, dolomite, building (slaked) lime, oyster shells and blast furnace slag which can be used for liming soil if finely grind.
Significance of Liming:
- To raise the soil PH
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Q. 1. Explain similarities and differences between industrial fertilizers and manure
Q. 2. To mention the advantages of straight and mixed fertilizers of N, P and K
Q. 3. Mention examples of straight and mixed fertilizers and classify them
Q. 4. Compare the relative advantages and disadvantages of manures as compare industrial fertilizers.
How to maintain and improve soil fertility:
A fertile soil provides all essential plant nutrients in amounts which are suitable for the growth of most plants.
How can a soil be made more fertile
1. Good cropping system
2. Adding manure to the soil
3. Adding industrial fertilizers to the soil
1.GOOD CROPPING SYSTEM:
Crop rotation should be practiced. Every season, another crop should be planted on a given field. Legumes should be rotated with cereals, shallow rooted plants with deep rooted ones .
2.ADDING MANURE:
Manures are organic materials that can be added to the soil to increase soil fertility.
E.g. Kraal manure – from cattle kraal
Farmyard manure – wastes from animals
Compost manure-mixture of soil and decomposing organic matter
Bio gas manure – from effluent of bio gas plants
3.ADDING INDUSTRIAL FERTILIZERS:
– Fertilizers are most inorganic compounds which contain one or more plant nutrients in a concentrated form.
E.g. Nitrogen fertilizers, phosphorus fertilizers, potassium fertilizers.
Similarities between manure and industrial fertilizers.
– They both increase humus to the soil and promote good soil structure
– Both manure and industrial fertilizers contain minerals Nitrogen, phosphorus and potassium which are essential for plant growth.
Differences between manure and industrial fertilizers
| Manure | Industrial fertilizers |
| 1. It is organic material | 1. It is inorganic compound |
|
2. It is composition varies depending on the type of manure |
2. It is composition is fixed |
| 3. It is less toxic | 3. It is toxic if used in large amounts |
| 4. It has low contents of nutrients | 4. It has high content of nutrients |
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