Soils of Pakistan
The soils in Pakistan are affected by arid climate, therefore belong to dry group, rich in basic having a high calcium carbonate content and poor in nitrogenous matter. They vary in color from reddish brown in north to red or gray in south. The soils at the foot of the mountains are sandy but become finer towards plains where lime concentration is occasionally found. These are derived from two types of parent materials:
Alluvium, loess and windblown sand. They are of mixed mineralogy. The deposited alluvium near the river is called khaddar and mostly consists of sand. The old alluvium of the bar uplands, called bangar consists of loams. The soils of Thal and the Thar deserts and Baluchistan are wind blown. In southern Potohar thin layer of residual silt is found. In parts of canal irrigation lands, salt afforescences are found, generally in the areas of high water table. These saline areas are known as thur or kallar.
Residual material obtained from weathering of underlying rocks. Most of the are calcareous. In some areas granites have produced non-calcareous soil material. Very small quantities of salts are released from most of the rocks. The therefore, essentially non-saline.
The soils of Pakistan have acquired distinct characteristics from the parent and by their mode of formation. The river-laid sediments have developed into alluvial soils. The desert sands have turned into distinct soils. The hills, mountains and the plateaus produced residual soils with patches of alluvial, loess and other soils. The soils of Pakistan can be classified into the following six soil types:
Alluvial Soils of the Flood Plains
The food conditions differ from one region to another within the flood plains of Pakistan. This is because areas close to rivers are flooded each year, areas away from rivers are inundated in years of severe floods, while coastal areas are subject to tidal flooding. This the sod texture, soil water, soil pH and other soil characteristics and led to development of different types of soils such as:
Loamy and sandy Soils: The soils develop in active flood areas and occupy the narrow strips along Indus river and its tributaries, the Jhelum, the Chenab, the Ravi Satluj. These soils are characterized by presence of sand and loam; however, the loam dominates the area.
Loamy and Clayey Soils: These soils are found in old flood plains that lie between the active flood plains and the Bar uplands in the northern Indus plains and between the active flood plains and the desert region in the southern Indus plains. These sods are considerably stable and homogenized with saline and alkaline patches found here and there. Loam is the predominant soil and pH ranges from 8.0 to 9.0.
Loamy Saline Estuarine Soils: These soils occupy a major part of Indus delta from levees to the back slopes of the Indus and its distributaries. These soils are low in organic matter, saline in most parts and their pH ranges from 8.0 to 8.5
Alluvial Soils of the Bar Uplands
These soils are located well above the flood plains in Kirans Bar, the Sandal Bar and Nili Bar areas. These soils are rich in lime, their texture is silt loamy and clay loamy, are quite fertile, and extensively cultivated with the help of irrigation.
Soils of the Piedmont Plains
These plains are found between Sulaiman-Kirthar mountains and the Indus river. Two relatively smaller areas occur in the norther part of the Punjab along the Pir Panjal mountains. The foothills of these mountains are occupied by stony fans formed of loose material washed down from the mountains by occasional rainfall. The stream beds are filled with gravel and stones. The soils are predominantly stony, strongly calcareous and of little agricultural importance.
Gently sloping plains lie beyond the foothills formed by alluvium laid down by flooding steams. These are covered mainly with sandy loams and silts and strongly calcareous. In some areas dunes have developed by wind action. The soils are quite fertile and produce good crops after rains and on application of irrigation.
There are three large areas of desert soils in Pakistan: Thar-Cholistan, Thai and Kharan, consisting of regosols. Thar-Cholistan is the most extensive desert located in the eastern Part of Pakistan and consists of sand dunes. The dunes are occupied by loamy sands. The soil are weakly developed, calcareous and rich in mineral.
The Thal area lies between the Indus and Jhelum rivers and is a river terrace covered with a comparatively thin layer of gray sands. Calcareous ridges and sandy loams are present between the dunes.
The Kharan desert occupies a large area of western Balochistan and is covered with sand.
Soils of Potwar Plateau
The Potwar plateau consists of loess, alluvial and residual soils. All these soils are eroded and characterized by presence of gullies.
The loess corer a small area, brown in color, moderately alkaline and very fertile but badly eroded.
The alluvial soils cover the narrow river valleys formed of fine sands and loams and alluvial terraces consisting of clay loams. They are fertile and are suitable for agriculture
The residual soils are derived from the decomposition of shale and sandstone. They are clayey soils rich in calcium carbonate. These soils are poor and suitable for pasture.
Soils of Western Hills
The Western hills are dominated by steep rocky bare soils. Some parts of the extreme north are covered with glaciers. The soils that cover the mountain and hills are lithosols and regosols, whereas the river valleys and basins are filled with alluvial soils.
The, soils found in Pakistan are grouped into six soil orders. These orders include 21 soil groups.
Aridsols: This order includes soils occurring in arid and semi-arid climates. These soils have cambic. sa!ic, calcic, and argillic diagnostic horizons.
Entisols: The soils that lack any soil profile development, except for some humification and homogenization in the surface horizon are included in this order.
Inceptisols: The soils that occur in humid and sub-humid areas of Pakistan are included in this order. These soils are non-calcareous or moderately calcareous and poor in organic contents.
Alfisols: The order comprises of three soil groups of non-calcareous, nearly soils found in high sub-humid climates; fairly well-developed, slightly calcareous soils of sub-humid areas of river terraces and loess plain; and saline-sodic soils have natric horizon.
Vertisols: This order includes clayey soils which occur in sub-humid areas. These soils are slightly or moderately calcareous.
Mollisols: This order comprises of soils rich in organic matter (mollic horizon) occur under cool, sub-humid highland climate.