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Intensive cultivation and improper nutrient replenishment have affected soil fertility.
Stagnating or declining yields are the telltales.
Soil plays a central role for economic and social development.
It ensures food, fodder, fiber and renewable energy supplies to sustain human, animal and plant life.
Since increasing cultivation area is difficult, the pressure is on increasing productivity of existing cultivated area.
However, in our urge to grow more food, soils have been particularly misused to an extent that it is now affecting the state of our health.
Soil degradation refers to decline in the soil’s productivity through adverse changes in nutrient status, soil organic matter, structural attributes, and concentrations of electrolytes and toxic chemicals.
In India, Soil health is showing signs of fatigue due to intensive cultivation, over-mining of nutrients by crops with lesser replenishments through organic and inorganic sources.
A national database on land degradation prepared by ISRO in 2016 shows that 120.7 million hectare (mha), or 36.7 % of India’s total arable and non-arable land, suffers from various forms of degradation with water erosion being its chief contributor in 83 mha (68.4 %).
Water erosion results in loss of organic carbon, nutrient imbalance, soil compaction, decline in soil biodiversity, and contamination with heavy metals and pesticides.
According to National Academy of Agricultural Sciences (NAAS), the annual soil loss rate in India is 15.35 tonnes per ha, resulting in loss of 5.37 to 8.4 million tonnes of nutrients.
The loss of soil has another immediate major impact on crop productivity.
The eroded soil causes siltation of reservoirs and reduces reservoir capacity which is estimated 1 to 2 % annually which further impact irrigation in its command area.
Major rainfed crops in India suffer an annual production loss of 13.4 million tonnes due to water erosion which amounts to a loss of Rs 205.32 billion.
Around 1.07 mha is under physical degradation due to waterlogging. 0.88 mha area is under permanent surface inundation and about 12.53 mha of rainfed soil remains fallow due to temporary water logging during kharif.
Waterlogging, which damages soil by causing salinisation, results in annual loss of 1.2 to 6.0 million tonnes of grain in India.
Besides India’s huge tract of fertile soils also get affected due to diversion for non-agriculture purposes.
Chemical degradation of soil health is based on parameters like salinisation (alkalinisation), acidification, soil toxification through chemicals, and depletion of nutrients and organic matter and other nutrient input related issues.
6.74 mha are under salt affected soils comprising of 3.79 mha under high sodicity (presence of sodium, pH > 9.5) and about 3 mha under high salinity.
In terms of pH value that major part of country is moderately Alkaline. Some part of North India like Himachal Pradesh, J&K (undivided), western Uttarakhand and East India like Odisha, Jharkhand, North Eastern and western coast peninsula are high or moderately acidic.
About 11 mha of arable land suffers from acute soil acidity (pH < 5.5) with very low productivity.
Soil toxification through chemicals is increasing with urbanisation.
A study by the Indian Institute of Soil Science, Bhopal, in 2015 indicated high concentration of heavy metals in composts manufactured in many cities of India from mixed municipal solid wastes.
These heavy metals may accumulate in soil with repeated applications.
Nutrient Deficient Soils:
In terms of major macro-nutrients (nitrogen-phosphorus-potassium, or npk), Indian soils are generally deficient in nitrogen and phosphorous, while high in potassium.
Phosphorous is low mostly in Indo-Gangetic plains, Central and North East India.
Also, nitrogen deficiency is across the country, with the deficiency higher in central and southern India than in the Gangetic plains.
The ideal n-p-k use ratio is 4:2:1, but has gone from 6:2.4:1 in 1990 to 6.7:2.7:1 in 2016.
The situation is grimmer in agriculturally important states like Punjab and Haryana where the ratio is as high as 31.4:8.0:1 and 27.7:6.1:1 respectively.
Skewed consumption of Fertilizer:
Even the consumption of fertilisers is concentrated in 42 % districts of India. Of the total 525 districts of the country, about 292 account for 85 % of total fertiliser use.
The pattern of use of fertiliser also varies widely among crops. Fertiliser use in potato, sugarcane, cotton, wheat and paddy is quite high at 347.2 kg/ha, 239.3 kg/ha, 192.6 kg/ ha, 176.7 kg/ha and 165.2 kg/ha respectively.
Even among these crops, there is excessive use of nitrogenous fertiliser. Excessive use of urea is further deteriorating the soil.
54th report of the Parliamentary Standing Committee of Agriculture (2017-18) says that skewed subsidy policy in favour of urea and high prices of other fertilisers are behind the imbalance in the use of fertilisers in the country.
The Soil Health Card (SHC) scheme, launched in 2015 with a budget outlay of Rs 568 crore under the National Mission for Sustainable Agriculture, aims to regulate and minimize the use of fertilizer.
The card which is issued to a farmer after an analysis of his / her land has recommendations on the dosage of different nutrients needed and encourages farmers to use fertilizers according to soil deficiencies.
The National Productivity Council, a government body that carries out research on productivity found that as a result of the application of fertilizers according to recommendations of SHCs, there has been an 8-10 percent decrease in the use of chemical fertilizers in the country.
However, even five years after they were introduced, the impact of SHC is not visible on the ground and the consumption of fertilizers has been increasing.
With changing climate, land degradation is expected to only increase due to high intensity storms, extensive dry spells, and denudation of forest cover.
In context of such large scale of soil degradation, India has vowed to restore 26 mha by 2030 at the 2019 meeting of the United Nations Convention to Combat Desertification.
For this to happen, there is need for adoption of integrated watershed approach agricultural intensification using innovative farming practices and to take steps to rationalise over usage of chemical fertilisers in country to restore fertility.
Also, Conservation agriculture (CA) coupled with other technologies like micro-irrigation, fertigation, and management of problem soils using specific technologies hold great promise to increase productivity of crops and fruits.
Source: Down To Earth.