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After reading this article you will learn about Calcareous Soil:- 1. Formation of Calcareous Soil 2. Characteristics of Calcareous Soil 3. Effects 4. Management.
Formation of Calcareous Soil:
Calcareous soil is formed in arid as well as humid regions. It is more common in arid areas. In dry regions, calcareous soil is formed in situ whereas, it has secondary origin in water-logged areas.
(A) Formation of Calcareous Soil in Situ by Weathering of Parent Rock Materials:
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There is formation of calcium carbonate (CaCO3) due to weathering of rocks. The low rainfall in arid and semi-arid regions, is not sufficient to leach out the soluble products of weathering to ground water. In dry weather, the salt moves up with the water by capillary movement to the surface where they are deposited.
(B) Development of Calcareous Soil by Secondary Origin:
Calcareous soil of secondary origin is developed in low-lying areas or in basin shaped areas. Generally, drainage is impeded in these low-lying areas. During the rainy season, soluble calcium bicarbonate of nearby areas accumulate in the low-lying areas. During dry season, calcium bicarbonate converted into calcium carbonate and deposited on the soil surface by capillary movement.
Characteristics of Calcareous Soil:
(i) Calcareous soil mainly contains calcium carbonate in free form and magnesium carbonate may remain present in small quantity.
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(ii) There is effervescence when calcareous soils come in contact with the acid.
(iii) Soil colloids contain about 90 per cent calcium and magnesium carbonate as adsorbed bases.
(iv) Such soils usually having about pH 8.0 but pH may range from 7.0 to 8.3.
Effects of Calcareous Soil:
(A) Physical Properties of Soil:
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(i) Calcareous soils remain in a flocculated condition (granulated). Soil is permeable to water and air due to large number of pore spaces.
(ii) Flocculation in heavy (clay) soil increases pore spaces and consequently drainage but in light (sandy) soil it decreases water-holding capacity.
(B) Availability of Nutrients:
(i) Phosphorus:
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In calcareous soil, the solubility of phosphorus is depressed which results in the decrease of P availability.
(ii) Potassium:
Availability of potassium is decreased due to presence of excess calcium carbonate.
(iii) Zinc:
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Availability of zinc is reduced.
(C) Activity of Microorganism:
Moisture is essential for microorganism activity. Microorganism activity in wet calcareous soil is normal but it is affected in dry calcareous soil.
Management of Calcareous Soil:
Management and reclamation of calcareous soil are not difficult because pH in such soil is not very high. Generally, there is no need of chemical amendments for reclamation of calcareous soil.
The calcareous soil can be managed in the following ways:
(i) Tillage Operation:
Light (sandy) calcareous soil develops large number of pore spaces due to flocculation. These type of soils have poor water-holding capacity. Therefore, such type of soil needs compaction by plank or roller to increase the water- holding capacity.
(ii) Application of Organic Manure:
When sufficient amount of farm yard manure, compost and green manure are added, the amount of carbon dioxide and acid increases and as a result pH of soil decreases.
(iii) Use of Chemical Fertilizer:
Availability of phosphorus is low in calcareous soil.
To increase the availability of P, the phosphatic fertilizers should be used in the following manner:
(a) Phosphatic fertilizers should be used near the roots of plant.
(b) Use of phosphatic fertilizers in ball form also increases its availability.
(c) May be used in split dose.
(iv) Use of Micronutrients:
Addition of micronutrients like, zinc, copper, iron would be helpful in increasing the yield.
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