Introduction

Soils with different layers have different physical and chemical properties. The topmost layer is humus or organic matter, topsoil followed by a transition zone, subsoil, weathered rock material and parent rock. In soil erosion topsoil is lost. Subsoil can’t support plant life.

Soil nutrients:

• Air – carbon, oxygen
• Water – hydrogen, oxygen
• Soil:
• Macronutrients: nitrogen, phosphorous, potassium, calcium, magnesium, sulfur
• Micronutrients: Boron, chlorine, iron, magnesium, iron, copper.

The ideal ratio of N, P, and K should be 4:2:1 but in India, it’s 8:4:1. Urea is out of Nutrient based subsidy and so is misused. Due to the high misuse of urea, there is nitrate pollution in the ground and water.

Soil health cards are issued by the government for providing information on the nutrient status of the soil and recommendation on the appropriate dosage of nutrients.

Implications:

• Soil and water pollution.
• Eutrophication of lakes.
• Nitrate poisoning in groundwater leads to stomach cancer
• Without humus, chemicals harden the soil and make it infertile.

Organic farming:

1. Paramparagat Krishi Vikas Yojana to promote organic farming, discourage the use of chemicals as inputs and promote bio-fertilizers, vermin compost, sustainable practices like crop rotation, and water efficiency.
2. Green manure is the sowing of crop seeds, sun hemp, and guar then mulching and plowing them into the soil to enrich N, and P in the soil.

Vermicompost:

A mixture of earthworms and organic waste. The earthworms break down the matter to give nutrient-rich, water soluble, moist organic fertilizers. It increases soil aeration, water retention, root growth, and microbial matter and is also affordable.

Soil forming factors are:

1.  Rock
2.  Climate
3.  Relief
4.  Biota
5.  Time

Rocks:

Soil is made up of erosion of soft rocks. It provides soil material, texture, porosity, and pH value. Soft rocks mean better soil formed than hard rocks.

Climate:

Wind, water, and glaciers are agents of erosion. Climate determines the type of erosion and its intensity.

Relief:

A steep gradient gives underdeveloped soil and a plain area gives well-developed soil.

Biota:

Microbes enrich the soil. Roots from plants help in weathering of rocks and humus content from plants enriches the soil.

Time:

Soil formation is a long-term process. Time decides the maturity of the soil.

Transportation in soil:

• Capillary:
• Upward movement of minerals.
• The hot and dry climate causes this.
• Salts within the soil come to the surface. This results in soil salinity.

 

• Leaching:
• Downward movement of minerals.
• Seen during the humid climate.
• Silica moves downwards but iron and aluminum remain on top. Thus we get laterite soils that are acidic and reddish.
• Gleying:
• In swamps peaty soil is formed.
• Excessive potassium is seen.

 Soil Conservation:

Structural solutions for soil conservation:

1.  Construction of retaining walls. Strengthen slopes of river banks using stone pitching or wire netting.
2.  On rivers construction of multi-purpose dams. Construction of tri-pods, tetra-pods, and groins to prevent erosion.

Nonstructural solutions:

1. Afforestation.
2. Discourage cultivation on marginal lands.
3. Agroforestry.
4. Along slopes: Contour bunding, terrace farming, basin listing, soil mulching, crop rotation, relay farming, strip farming, organic farming, and use of biofertilizers.
5. To control wind erosion transverse farming and shelterbelts.

Soil Salinity:

Causes:

•   Arid regions are created due to salts on the upper layers of the soil.
•  Bad drainage due to basin topography and black cotton soil
•  Faulty agriculture practices like over-irrigation, and cultivation of water-intensive crops.
•  Seawater intrusion into groundwater reserves.

Implications:

•   Salts of sodium, potassium, and manganese come to the topsoil.
•  Soil fertility is reduced.
•  Choice of crops is reduced to only salt-resistant varieties like cotton, barley
•  Quality of fodder reduced.
•  Reduced infiltration of water into the ground.

Solutions:

•  Soil is flushed with water and salts are dissolved and removed but this method cant is used in India.
•  Laying drainage pipes underground to pump out excessive water.
•  The lining of canals to avoid seepage.
•  Use of agents like gypsum and sodium pyrite to recover soil.
•  Discourage the use of groundwater and encourage rainwater harvesting, and agro-climatic farming.

Desertification:

•  An extreme form of land degradation in semi-arid or sub-humid areas. Expansion of desert areas.
•  It cant be reversed only prevented.

    Solutions:

• Constructing retaining walls.
• Growing grass on sand dunes.
• Cultivation of trees on margins
• Transverse farming

Types of Soils:

1. Alluvial Soil

•  Covers 42% of India.
•  Deposited by rivers. Well-drained. Most fertile.
•  Covers the northern plains. Fertility and productivity decreased but productivity increased. These soils are both well-drained and poorly drained. In general, they have an immature profile in undulating areas, while in the leveled areas they have a well-developed and mature profile. The Khadar type Solis is low-lying and frequently inundated by floods during the rainy season. Thus, the khadar occupies the flood plains of the rivers and is enriched by fresh silt deposits every year. The khadar tracts are generally rich in concretions, and nodules of impure calcium carbonate or Kankar. In the drier areas, it also exhibits stretches of saline and alkaline efflorescences. The Bhangar type of soil is above the flood level. It is generally well-drained but contains concretion (kankars] of impure calcium carbonate. The soil texture varies from loamy soil to clayey-loam. It is well-drained and rich in humus, phosphoric acid, lime, and organic matter. Alluvial soils are, however, deficient in potash.

2. Red Soil

•  Covers 25% of the country.
•  Formed due to erosion of granite and gneissic rocks. Best drained soil, least susceptible to waterlogging. Most vulnerable to soil erosion.
•  Lacks nitrogen, and phosphorous. Supports max crop diversity. Their color is mainly red because of the presence of ferric oxides. Generally, the top layer is red, while the horizon below is yellowish in color. The texture of red soils varies from sand to clay and loam. Their other characteristics include porous and friable structure, absence of lime, kankar, and carbonates, and a small number of soluble salts. In general, these soils are deficient in lime, phosphate, magnesia, nitrogen, humus, and potash. Intense leaching is a menace to these soils. In the uplands, they are thin, poor, gravelly, sandy, or stony and porous, light-colored soils, but in the lower plains and valleys, they are rich, deep, dark-colored fertile loams.

3. Black soil

•  Covers 15% of India.
•  Formed from erosion of volcanic rock. Lacks nitrogen and phosphorous.
•  High water retention. Cracks when dry so self plowing and sticky when wet. In general, these soils have a clayey texture and are rich in iron, lime, calcium, potash, aluminum, and magnesium. They are, however, deficient in organic matter. When the soil is wet, it becomes difficult to plow the field as the plow gets stuck in the mud. It is a matured soil and also known as Regur (cotton soil) soil.

4. Laterite soil

•  Found in areas with the alternate wet-dry season. Used for making bricks. The red color of the soils is due to the presence of iron oxide. These soils developed mainly in the highland areas of the plateau. The soils in the higher areas are generally more acidic than those in the low-lying areas. These soils are rich in iron and aluminum, but poor in nitrogen, potash, potassium, lime, and organic matter. Although they have low fertility, they respond well to manuring.

5. Mountainous soil

•  Immatured soil. Cant support agriculture due to the steep slopes but can grow grass and shrubs.
•  Good for lumbering.
•  Leaves of coniferous trees are hard to degrade. A cold climate slows bacterial growth.

6. Desert soils

•  Sandy, is loose and friable with a low water retention capacity. It cants support agriculture.
•  But Indian desert soil is suitable for agriculture under irrigation as its made of aluminum deposits. The desert soils are sandy to gravelly with low organic matter, low nitrogen, and varying percentage of calcium carbonate. These soils contain a high percentage of soluble salts, but have low moisture content and low water-retaining capacity.

7. Mangrove soils

•  Bluish-green color due to sulfide.
•  Cant support plants but only mangroves. Present in coastal areas of all states.

 Karewa Soil

• • Karewas are the lacustrine deposits in the Valley of Kashmir. These are the flat-topped mounds that border the Kashmir Valley on all sides. They are composed of fine silt, clay, sand, and bouldery- gravel. They are characterized by fossils of mammals and places by peat.

• • The karewas are mainly devoted to the cultivation of saffron, almond, walnut, apple, and orchards. The karewas, devoted to saffron cultivation are fetching good income to the growers.

Snowfields

• • The area under snow and glaciers is about 4 million hectares. The high peaks of the Greater Himalayas, Karakoram, Ladakh, and Zaskar {Zanskar} are covered by ice and glaciers.

• • The soils in these areas are immature, generally, without soil erosion, It remains frozen and is unsuitable for the cultivation of crops.

Soil alkalinity:

    1.  Calcium salts in the upper layer cause moderate salinity. But in the next stage sodium, and potassium salts are in the upper layer.

2. This is due to bad drainage and over-irrigation.

Land use in India:

1.  India is home to 17% of the population but 2.4% of the land in the world.

                                                           TABLE 1: LAND USE IN INDIA

 

Land use	Percentage
Net son area	46
Forests	23
Land not available for agriculture [cities, development infra]	15
Fallow land	12.5
Pastures	3.5

Miscellaneous

• Desired land use wants to increase forest cover to 33%. Development land should be increased and fallow land reduced.
• India also has the highest percentage of dairy animals but isn’t a leading exporter of dairy products.
• India’s Net Sown Area [NSA] is 10% of the world’s agricultural area but low productivity is seen.
• India has more natural potential for agriculture than china.
• India’s NSA is more than china’s. India’s Gross sown area [GSA] is 199 million hectares. Irrigated land = 61 million hectares.
• Cropping intensity = G.S.A / N.S.A = 140% target = 160%