There is a wide range of soil types in India. Soils get their distinguishing features from the parent rocks, which are sieved by flowing water, sliding glaciers, and drifting wind and are deposited on landforms such as river valleys and coastal plains. The process of sieving such soils has led to deposition of materials in layers without any marked pedologic horizons, though it has altered the original chemical composition of the soils.

Common types of soils are the red-to-yellow (including late rite) and black soils. After these the alluvial soil is the third most common type. Also significant are the desert soils of Rajasthan, the saline soils in Gujarat, southern Rajasthan, and some coastal areas, and the mountain soils of the Himalayas. The type of soil is determined by numerous factors, including climate, relief, elevation, and drainage, as well as by the composition of the underlying rock material. These soils are encountered over extensive no alluvial tracts of peninsular India and are made up of such acidic rocks as granite, gneiss, and schist. They develop in areas in which rainfall leaches soluble minerals out of the ground and results in a loss of chemically basic constituents; a corresponding proportional increase in oxidized iron imparts a reddish hue to many such soils. Hence these are commonly described as ferralitic soils. In extreme cases, the concentration of oxides of iron leads to formation of a hard crust, in which case they are described as lateritic (for later, the Latin term meaning “brick”) soils. The heavily leached red-to-yellow soils are concentrated in the high-rainfall areas of the Western Ghats, the western Kathiawar Peninsula, eastern Rajasthan, the Eastern Ghats, the Chota Nagpur Plateau, and other upland tracts of northeastern India. Less-leached red-to-yellow soils occur in areas of low rainfall immediately east of the Western Ghats in the dry interior of the Deccan. Red-to-yellow soils are usually infertile, but this problem is partly ameliorated in forested tracts, where humus concentration and the recycling of nutrients help restore fertility in the topsoil.

The black soils found in the lava-covered areas are the most conspicuous. These soils are often referred to as regur but are popularly known as “black cotton soils,” since cotton has been the most common traditional crop in areas where they are found. Black soils are derivatives of trap lava and are spread mostly across interior Gujarat, Maharashtra, Karnataka, and Madhya Pradesh on the Deccan lava plateau and the Malwa Plateau, where there is both moderate rainfall and underlying basaltic rock. Because of their high clay content, black soils develop wide cracks during the dry season, but their iron-rich granular structure makes them resistant to wind and water erosion. They are poor in humus yet highly moisture-retentive, thus responding well to irrigation. These soils are also found on many peripheral tracts where the underlying basalt has been shifted from its original location by fluvial processes. The sifting has only led to an increased concentration of classic contents.

Alluvial soils are widespread. They occur throughout the Indo-Gangetic Plain and along the lower courses of virtually all the country’s major rivers (especially the deltas along the east coast). Narrow ribbons of alluvium also mark the no deltaic plains along India’s coasts.

New alluvium found on much of the Indo-Gangetic floodplain is called khadar and is extremely fertile and uniform in texture; conversely, the old alluvium on the slightly elevated terraces, termed bhangar, carries patches of alkaline efflorescence, called usar, rendering some areas infertile. In the Ganges basin, sandy aquifers holding an enormous reserve of groundwater ensure irrigation and help make the plain the most agriculturally productive region of the country.

Fertilizers :Inorganic fertilizers (mineral fertilizer): Naturally occurring inorganic fertilizers include sodium nitrate, mined rock phosphate, and limestone (to raise pH and a calcium source).

Macronutrients and micronutrients:Fertilizers can be divided into macronutrients and micronutrients based on their concentrations in plant dry matter. There are six macronutrients: nitrogen, phosphorus, and potassium, often termed primary macronutrients because their availability is usually managed with NPK fertilizers, and the secondary macronutrients — calcium, magnesium, and sulfur — which are required in roughly similar quantities but whose availability is often managed as part of liming and manuring practices rather than fertilizers.

The macronutrients are consumed in larger quantities and normally present as a whole number or tenths of percentages in plant tissues (on a dry matter weight basis). There are many micronutrients, required in concentrations ranging from 5 to 100 parts per million (ppm) by mass. Plant micronutrients include iron (Fe), manganese(Mn), boron (B), copper (Cu), molybdenum (Mo), nickel (Ni), chlorine (Cl), and zinc (Zn).

Synthesized materials are also called artificial, and may be described as straight, where the product predominantly contains the three primary ingredients of nitrogen (N), phosphorus(P), and potassium (K), (known as N-P-K fertilizers or compound fertilizers when elements are mixed intentionally).

Such fertilizers are named according to the content of these three elements. For example, if nitrogen is the main element, the fertilizer is often described as a nitrogen fertilizer.

Health and sustainability issues:Many inorganic fertilizers do not replace trace mineral elements in the soil which become gradually depleted by crops. This depletion has been linked to studies which have shown a marked fall (up to 75%) in the quantities of such minerals present in fruit and vegetables.

When used appropriately, inorganic fertilizers enhance plant growth, the accumulation of organic matter, and the biological activity of the soil, thus preventing overgrazing and soil erosion. The nutritional value of plants for human and animal consumption is typically improved when inorganic fertilizers are used appropriately.

There are concerns regarding arsenic, cadmium and uranium accumulating in fields treated with fertilizers. The phosphate minerals contain trace amounts of these elements and if no cleaning step is applied after mining the continuous use of phosphate fertilizers leads towards an accumulation of these elements in the soil.

Phosphate fertilizers replace inorganic arsenic naturally found in the soil, displacing the heavy metal and causing accumulation in runoff .Eventually these heavy metals can build up to unacceptable levels and build up in produce.

Another problem with inorganic fertilizers is that they are now produced in ways which cannot be continued indefinitely. Potassium and phosphorus come from mines (or saline lakes ) and such resources are limited. Nitrogen sources are effectively unlimited (forming over 70% of atmospheric gases), however, nitrogen fertilizers are presently made using fossil fuels such as natural gas and coal, which are limited.

Organic fertilizers ('natural' fertilizer): Naturally occurring organic fertilizers include manure, worm castings, seaweed etc. Cover crops are also grown to enrich soil as a green manure through nitrogen fixation from the atmosphere by bacterial nodules on roots as well as phosphorus (through nutrient mobilization) content of soils.

Processed organic fertilizers from natural sources include compost (from green waste), bloodmeal and bone meal (from organic meat production facilities and others.

Benefits of organic fertilizer : However, by their nature, organic fertilizers provide increased physical and biological storage mechanisms to soils, mitigating risks of over-fertilization. Organic fertilizer nutrient content, solubility, and nutrient release rates are typically much lower than mineral (inorganic) fertilizers.

Organic fertilizers had released between 25% and 60% of their nitrogen content

Controlled release fertilizers (CRFs) had a relatively constant rate of release

Soluble fertilizer released most of its nitrogen content at the first leaching Disadvantages of organic fertilizer

It is difficult to chemically distinguish between urea of biological origin and those produced synthetically.Like chemical fertilisers, it is possible to over-apply organic fertilizers if does not measure and distribute the required amounts according to the recommended amounts for the plot of land in question. Release of the nutrients may happen quite suddenly depending on the type of organic fertiliser used.

Environmental risks of fertilizer use: High application rates of inorganic nitrogen fertilizers in order to maximize crop yields, combined with the high solubilities of these fertilizers leads to increased leaching of nitrates into groundwater.

Eventually, nitrate-enriched groundwater makes its way into lakes, bays and oceans where it accelerates the growth of algae, disrupts the normal functioning of water ecosystems, and kills fish.

The use of ammonium nitrate in inorganic fertilizers is particularly damaging, as plants absorb ammonium ions preferentially over nitrate ions. This allows excess nitrate ions which are not absorbed to be freely dissolved (by rain or irrigation) into groundwater and other waterways, leading to eutrophication.

For these reasons, it is recommended that knowledge of the nutrient content of the soil and nutrient requirements of the crop are carefully balanced with application of nutrients in inorganic fertilizer. This process is called nutrient budgeting. By careful monitoring of soil conditions, farmers can avoid wasting expensive fertilizers, and also avoid the potential costs of cleaning up any pollution created as a byproduct of their farming.

Hazard of over-fertilization: Over-fertilization of a vital nutrient can be as detrimental as underfertilization. "Fertilizer burn" can occur when too much fertilizer is applied, resulting in a drying out of the roots and damage or even death of the plant.

Environmental toxicity of fertilizer: Toxic fertilizers are recycled industrial waste that introduce several classes of toxic materials into farm land, garden soils, and water streams. This is leading to major environmental problems due to the fact of toxic waste being processed and planted into our land and water. The most common toxic elements in this type of fertilizer are mercury, lead, and arsenic. Let us read our awareness in this matter.

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