The naturally occurring thin layer of unconsolidated material on the earth surface that has been influenced by parent material, relief, climate, in addition to physical, chemical, biological agents to produce a medium, suitable for the growth of the plants is called soil. Soil exhibits differences in their physical and chemical characteristics as well as in their capability for growing crops.
Soils of any region may be classified into:
- zonal, in broad altitudinal zones or belts;
- Inter-zonal, resulting from special parent rocks (e.g. Limestone, sandstone);
- Azonal or immature soils, new material on which soil-forming processes have not had sufficient time to work
The agriculture department of Himachal Pradesh has classified the soils into five types, taking into consideration the climate and the altitude.
Low Hill Soil Zone:
This Hill Soil Zone extends up to an elevation of about 900 metre. In this zone the soils are shallow and embedded with stone. Soil reaction is almost neutral; carbon to nitrogen ratio is 10:1. The nutrient status varies from low to medium. These soils are devoted mainly to rice, barley, wheat, and Maize and fodder crops. Leeching of soils on the slopes is the main problem in this zone.
Mid-Hill Soil Zone:
The Mid-Hill Soil Zone extends between 900 metre to 1500 metre.The soils are loam to clayey-loam in texture with grayish brown colour and are well drained. The carbon to nitrogen ratio varies between 10:12. These soils are neutral to slightly acidic in reaction. Available nitrogen and phosphate are medium, whereas, available potash varies from low to medium.
High Hill Soil Zone:
The High Hill Soil Zone extends between 1500-2000 m and has developed on steep slopes with good drainage. Soil texture ranges from silty loam to clayey loam with dark brown colour. On favourable aspects, the soils are quite deep. The organic matter is also high. The available nitrogen varies from medium to high, whereas, potash is medium. The soil react ion is acidic to neutral. Soil erosion is a serious problem in this zone.
Mountain Soil Zone:
The Mountain Soil Zone extends between 2100-3000 m. These soils are shallower in-depth than the high hill soils. Soil texture is silty loam to loam, with dark brown to light brown colour Soil reaction is slight to moderately acidic. The organic content varies from 2.5 to 3.5. The available nutrient status is medium to high. These soils are not very much used for agricultural purposes.
The Dry Hill Soil Zone:
These soils are found in Lahaul and Spiti, Pangi and Kinnaur where monsoon rainfall is scanty. These are high textured soils with variable fertility. The organic content and humus in the soil are low.
Middleton classification of soils:
However, people take a utilitarian view of soils, distinguishing between lands lying close to or at a distance from the homestead and between lands that yield one or two crops. Middleton in his final report on Land Revenue Settlenwnt has classified soils as under:
- Chaih—Irrigated by wells.
- Nehri 1—land irrigated by gravity Canals which are perennial in character.
- Nehri I—Land receiving water from the non-perennial source or only at times.
- Nad—Inundated land, growing only rice crop.
- Dofasli—Unirrigated—Bearing two crops a year or three in two years.
- Ek-Fasli (unirrigated)—This type of land produces only one crop in a year.
- Bahnd Banjar —It bears one crop in two to three years. The per acre yield is generally poor.
- Kharetar—These are hay-fields and pastures
Soils on the basis of their development and physicochemical properties:
The soils of the State can also be broadly divided into nine groups on the basis of their development and physicochemical properties. These are:
Alluvial soils: Alluvial soils are characterized by the incipient profile development and are found in Una (Una district), Indora (Kangra district) and Poanta (Sirmaur district) areas where floodplain is a dominant physiography. These soils correspond to Udifluvents and Eutrochrepts in accordance with Soil Taxonomy of USDA (Soil Survey Staff, 1990). These are generally coarse textured soils comprising loamy sand and sandy loam and occasionally loam to sandy clay loam, low in organic matter and neutral (pH >6.5) in reaction. The soils are somewhat calcareous in nature in which calcium carbonate varies from 2.0 to 4.5 per cent.
Brown hill soil: Brown hill soils are Sandy loam to clay loam texture found in Nahan (Sirmaur district) and Solan (Solan district) areas. These soils are medium to high in organic matter and neutral to slightly acidic in reaction. According to the soil taxonomy, the soils are classified as Hapludols, Hapludalfs and Udorthents.
Brown earth: Non-Calcic Brown soils are generally found in parts of Hamirpur, Bilaspur and Mandi districts besides Dehra Gopipur (Kangra district) areas. Soil reaction is neutral in most cases and rarely acidic. The texture varies from loamy sand to clay loam. Organic matter content varies from low to medium. These soils are equivalent to Eutrochrepts and Hapludalfs according to Soil Taxonomy of USDA.
Brown forests soils: Brown Forest soils are found in parts of Chamba districts where there is forest vegetation. These have moderately deep to deep solum. The soils are sandy loam to clay loam in texture and slightly acidic to neutral in reaction. The soils belong to Hapludalf, Hapludolls and Eutrochrepts groups in order of their occurrence.
Grey wooded or podzolic soils: Grey Wooded or Brown Podzolic Soils commonly developed under the varying magnitude of podzolization are found in parts of Shimla and Kullu districts and Karsog area of Mandi district. They are generally characterized by darker colours containing high organic matter. Soil reaction ranges from slightly to strongly acidic and the textures are sandy loam to clay loam. The soils belong to Hapludolls and Hapludalfs groups.
Grey brown podzolic soils: Grey Brown Podzolic soils are formed by the dominant process of podzolization and are found in parts of Kangra district and Jogindernagar area of Mandi district. They are distinctly acidic in reaction, heavy texture of clay loam silt loam and silty clay soils. In soil taxonomy these soils are classified as Paleudalf, Hapludalf and Haplorthods.
Planosolic soils: Planosolic Soils These imperfectly drained soils are found in Balh valley of Mandi district, Ghumarwin of Bilaspur district, Nagwain area of Kullu district and Saproon valley of Solan district. Soils are medium to fine-textured i.e. sandy loam to sandy clay loam and clay loam and neutral in reaction. Organic matter is usually medium to high whereas available phosphorus and potassium are rated under medium categories. These soils are placed in Ochraqualfs, Hapludalfs and Haplaquepts groups under soil taxonomy.
Humus and iron podzols: Humus and Iron Podzols are formed under the process of podzolisation. They are mainly confined to parts of Shimla, Dalhousie and Manali regions. These soils have dark coloured A horizon, enriched with organic matter, acidic in reaction, and reddish brown to yellowish brown B2 horizon contains free iron and aluminum accompanied by organic matter. Profiles are marked by distinct spodic horizon underlying Mollic or Umbric epipedon.
Alpine humus mountain speletal soils: Alpine Humus Mountain Skeletal Soils are found in the Himalayan highlands constituting the districts of Kinnaur, Lahaul-Spiti and Pangi tehsil of Chamba district where the precipitation is low and temperature is frigid. Soils are gravelly loamy sand to loam, usually high in organic matter and neutral in reaction. Available phosphorus and potassium are generally medium to high. On the basis of soil taxonomy, these soils can be classified as Hapludolls, Eutrochrepts and Udorthents.
In the State of Himachal Pradesh, soils are adversely affected by soil-erosion. The removal of organic matter and plant nutrients from the top layer and its leaching by the agents of denudation is called soil erosion. Unchecked erosion gradually leads to poverty of soil and undermines the strength of the land. Although there are a number of physical and socio-cultural factors responsible for the depletion and erosion of soil. The aspect of slope, precipitation, weather, temperature, wind, snowfall human action (overgrazing, defective crop-rotation) all combine to accentuate the rate of soil erosion. In order to overcome the problem of soil depletion and soil erosion, some of the important devices which need to be adopted are as under.
The soil erosion can be checked by:
- the maintenance of an effective vegetation cover,
- contour ploughing,
- rotation of crops,
- planting of cover crops,
- creation of windbreaks (trees, fences),
- pipe-drainage to prevent gullying,
- damning of gullies or filling them with brushwood.