Soil: Problems & measures of it's Conservation
Soil: -
“Soil is the loose surface material consisting of inorganic particles and organic matter that covers most of the land surface. Soil provides the structural support and the source of water and nutrients for plants used in agriculture”.
Soil is a material composed of five ingredients — Minerals, Soil organic matter, Living organisms, Gas, and Water. Soil minerals are divided into three size classes — Clay, Silt, and Sand; the percentages of particles in these size classes is called soil texture. The mineralogy of soils is diverse. For example, a clay mineral called smectite can shrink and swell so much upon wetting and drying that it can knock over buildings. The most common mineral in soils is quartz; it makes beautiful crystals but it is not very reactive. Soil organic matter is plant, animal, and microbial residues in various states of decomposition; it is a critical ingredient — in fact, the percentage of soil organic matter in a soil is among the best indicators of agricultural soil quality. Soil colours range from the common brown, yellow, red, grey, white, and black to rare soil colours such as green and blue.
Problems with Soil: -
Even though our country is blessed with wide varieties of soils with high fertility, it is being degraded day by day by various natural and human activities. Farmers in India are complaining about low productivity because of various reasons and soil degradation is one of them. Loss of soil fertility results in low productivity. It also results in high cost-of-production, low income, food scarcity, loss of biodiversity etc. As food security is a major concern, India must overcome the challenge of low productivity due to soil degradation. Conservation of soil is the only way to override this problem.
India is on the verge of a looming soil crisis that can potentially impact its agriculture soon. A third or 120 million hectares of soil of the total 350 million hectares has already turned problematic.
The reasons for the declining health of the soil is that they are either acidic, saline, sodic or alkaline soils. Whatever be the name, the net result is the poor health can have a big impact on agriculture productivity, sustainability and on human health, says a report brought out by a consortium of agriculture institutes.
Soil is the key to ecosystem services, as it plays a vital role in carbon cycle, storing and filtering water. The organic matter content, on an average, has gone down to a critical level of 0.3 to 0.5 per cent and several micro-nutrient deficiencies are surfacing rather quickly in different parts of the country, the report released on World Soil Day on 5th of December 2019 observed.
For India, which has over 17 per cent of the world population with limited land resources, the current situation warrants immediate attention and urgent remedial measures. In fact, a national policy to address the critical issue is needed, says MANAGE, one of the institutes in the consortia.
According to V. P. Sharma of Manage, the Centre has been briefed about the evolving situation. Countries such as Germany and even Kenya have national soil policies. Two institutes -- the Institute of Soil & Water Conservation, Dehradun and the Indian Institute of Soil Sciences (IISS), Bhopal are involved in studying some aspects of soil.
Giving an example of the emerging crisis, Sharma said the carbon content in soils is less than one per cent in the plains and around 2 per cent in the hill states of the country. Compare this with the world average of 4 per cent. Similarly, the increasing salinity and decreasing carbon content do not bode well for the future of agriculture.
The declining response ratios due to excess spraying of fertilisers, which leads to wasteful expenditure on fertiliser subsidy, only leads to loss of key national resources. This will affect human health, as agriculture produce is deficient in nutrition values.
India has a varied geological, climate and vegetation, which gives it different soil types. It takes thousands of years to make one-metre depth of soil, therefore, there is no option before the country but to halt and reverse the deterioration, so that the ability to feed billions and meet their nutrition needs is not severely impacted, the report says.
Major causes of soil degradation: -
- Soil erosion
- Decline of soil fertility
- Water logging
- Salinity
- Shifting cultivation
Soil erosion:
Among the agents, water is considered as the main cause of soil erosion.
Main agents of soil erosion are
(1) Water,
(2) Wind,
(3) Waves and
(4) Glaciers
Removal of the top layer of soil by various means, which include both natural events and human activities, is called as soil erosion.
Water-caused soil erosion can be classified as below:
- Sheet Erosion: Uniform removal of the topsoil just like a sheet.
- Rill Erosion: Heavy water flow cause rill in Land.
- Gully Erosion: Rill will enlarge as Gullies and land will be disordered. ( eg: Chambal Valley)
Note: Wind erosion also causes sheet and rill erosions.
Note: The largest area affected by soil erosion in India is the State of Rajasthan followed Madhya Pradesh.
- The fertility of topsoil will be lost.
- Nutrients content will decline as they are washed away by erosion.
- Underground water level will be reduced.
- Loss of vegetation and habitat.
- Drought and flood become frequent.
- Rivers get dried off.
- Adversely affect the economy and culture.
- Natural hideouts are formed when gully erosion occurs (Ex: Chambal valley was famous for criminal’s hideout).
Problems arising due to soil loss: -
- Deforestation
- Leaching
- Erosion
Deforestation leads to loss of top soil, soil erosion, nutrient leaching. It takes 2,000 years for the top soil to develop. Due to deforestation, on open, bare land, soil gets dissipated or carried away by monsoon rains and deposited in rivers, tanks and ponds, thus leading to silt formation, thereby reducing their water holding capacity. The exposed poor soil in agricultural lands makes it unfit for cultivation.
Soil erosion occurs due to wind and rain. Prolonged soil erosion may lead to formation of gullies and may lead to landslides.
Acidic Soils
In humid regions where rainfall is high, the continued leaching of soils results in the replacement of calcium, magnesium, potassium and sodium ions by hydrogen ions, leading to the formation of acidic soils. Lime application neutralises to some extent the acidity in the soil.
Crops like millets, oats, peas and soyabeans, can tolerate moderate acidity and trees like Derris indica, Gliricidia and Tamarind can be grown in this soil.
Saline Soils
In India around 7 million hectares of land are saline in nature. This soil contains toxic concentrations of soluble salt in the root zone. Because of the white encrustation due to salts, the saline soil is also called white alkali. The salinity may increase due to a rise in the water table, water-logging in the root zone and sea coast irrigation. Excess soluble salts like chlorine, sulphate, sodium and calcium will be present. Tree species like Azadirachta indica, Prospis julliflora, Terminilia arjuna and Albizia lebbeck can be grown in these soils. While planting, ridge-trench method, sub-surface planting and planting in furrow irrigation channels would help to reduce the toxicity of salts.
Alkaline or Sodic Soils
These soils do not contain any neutral salts. Because of high alkalinity resulting from sodium carbonate, the surface soil appears discoloured and black. Such soils have a very low infiltration rate. If the soil texture is heavy, gypsum can be added. Silt and rice husk can also be added to improve the texture. Trees like neem, Albizia lebbeck, Derris indica, Subabul, Prosopis and terminilia arjuna can be planted.
Decline of soil fertility: -
- Soil fertility is mostly affected in the states of Punjab, Haryana, and U.P.
- It is a condition when the soil is not giving enough production even though adequate irrigation and nutrients are supplied.
The major reasons for decline of soil fertility are:
- Frequent cropping,
- Unscientific rotation of crops,
- Extensive and excessive use of chemical fertilizers,
- Too much use of chemical pesticides.
- Land should leave uncultivated for a period and let to retain its fertility. Cropping after cropping will leave the land unfertile.
- Leguminous plants can be cultivated in intervals which will increase the fertility of the soil.
Water logging: -
- If there is no proper drainage system in the land, the land will become waterlogged.
- This results in the saturation of crops.
- The normal circulation of air will not be possible due to water logging and the amount of oxygen in the soil will decline.
- Construction of proper drainage system to allow water flow away from the land is the best way to reduce water logging.
Salinity: -
- Soil will become saline or alkaline in low rainfall areas. Rajasthan is an example.
- When the sea water enters the land, the soil becomes saline.
- The presence of calcium carbonate beneath (kankar) the soil will act as impermeable to water and water gets logged as happened in Indira Gandhi canal regions of Rajasthan. If the soil contains salt content, it will spread to the whole land due to this.
Shifting / jhum cultivation: -
- It is a type of cultivation practiced mainly in North-Eastern states of India
- It is a type of slash and burn method of cultivation.
- After reaping the crops, the land (usually the forest) is slashed and burned. The next cultivation will be in another plot and the burned land will let uncultivated for a period.
- In the early periods, the gap between two cultivations in a land was 10-20 years.
- Due to population increase and availability of land is reduced, the gap decreased to merely 2-3 years.
- This causes major deforestation, environmental pollution, loss of habitat for wild animals etc.
- The burning of forest results in soil erosion and gradual degradation of soil.
Soil conservation methods: -
- Afforestation.
- Contour ploughing (cultivation against the direction of the wind).
- Strip cultivation (cultivation in strips).
- Flood control by government initiatives.
- Reclamation of badlands.
- Windbreaks inland; like trees at borders.
- Organic farming.
- Control/restrict shifting cultivation.
- Construction of proper drainage.
- Levelling of gullies, ravines etc.
- Control of chemical fertilizers and pesticides in the market.
- Proper awareness about the need of conservation.
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