Fertilizers and manures are substances that are applied to crops to enhance their productivity and yield. Manures come from natural sources, whereas fertilizers are generated synthetically in factories. However, the fertilizers and manures, when applied at inappropriate times and quantities and when they contain harmful chemicals, will pollute the soil and affect its nature and composition drastically. Ammonium sulfate, ammonium phosphate, ammonium nitrate, urea, and ammonium chloride are some examples of chemical fertilizers. Cattle dung, urine, and slurry from biogas plants are excellent examples of manures. This article will explain to you about the fertilizers and manures as a source of soil pollution which will be helpful in preparing the Environment syllabus for the UPSC Civil service exam.

Types of Fertilizers

Organic Fertilizers

• Natural fertilisers derived from plants and animals are known as organic fertilisers.
• It adds carbonic chemicals to the soil, which are necessary for plant growth.
• Organic fertilisers boost the soil's organic matter content, promote microorganism growth, and alter the soil's physical and chemical qualities.
• It is one of the most important nutrients in green foods.
• The following products can be used to make organic fertilisers:
  • Agricultural Waste
  • Livestock Manure
  • Industrial Waste
  • Municipal Sludge

Inorganic Fertilizers

Chemical fertilisers containing nutritional elements for crop growth generated by chemical processes are known as inorganic fertilisers. The following are examples of inorganic fertilisers:

1. Nitrogen Fertilizers

• Nitrogen fertilisers contain nitrogen, which is essential for crop development.
• The key component of chlorophyll that keeps the photosynthesis process balanced is nitrogen.
• It is also found in plants as part of the amino acids that make up protein.
• Nitrogen fertilisers boost agricultural product production and quality.

2. Phosphorus Fertilizers

• Phosphorus is the most important nutrient in phosphorus fertilisers.
• Fertilizer efficiency is determined by effective phosphorus concentration, fertilisation methods, soil conditions, and crop strains.
• Phosphorus, which is contained in the cell's protoplasm, is vital for cell growth and proliferation.
• The use of phosphorus fertiliser is favourable to the growth of plant roots.

Types of Manures

Green Manure

• Green manure raises the organic matter content of the soil.
• Such manures have deep roots that penetrate the soil.
• These aid in the control of weeds as well as the avoidance of soil erosion.
• Legumes such as vetch, clover, beans, and peas; grasses such as annual ryegrass, oats, rapeseed, winter wheat, and winter rye; and buckwheat are examples of green manures.

Farmyard Manure

• Farmyard manure is a natural fertiliser that helps to improve the soil structure.
• It expands the capacity of the soil to hold more water and minerals.
• It also boosts the soil's microbial activity, which improves mineral delivery and plant nutrition.
• Examples of farmyard manures include cattle shed wastes-dung, urine, sewage, sludge, poultry wastes, droppings of sheep and goat and fish wastes.

Compost Manure

• It improves the soil structure as well as its water and nutrient retention capacity.
• As a result, the nutrient value increases, and the plants' health improves.
• Examples of compost manures include food scraps, grass clippings, leaves, wood chippings and coffee grounds.

Advantages of Fertilizers and Manures

Fertilizers

• They restore soil fertility and provide plant nutrients quickly.
• They are lightweight and transportable.
• Plants easily absorb fertilizers.
• Many crops, such as wheat, maize, and rice, benefit from fertilisers, which boost and raise their yield.
• However, these are chemicals, and if applied frequently, they have the potential to reduce soil fertility. Additionally, it pollutes water bodies.

Manures

• It improves the soil's water-holding capacity.
• It makes the soil porous and allows gases to flow freely.
• The soil improves in texture by the application of manures.
• In the soil, the number of bacteria grows as a result of applying manures.
• However, there are numerous disadvantages to using manure. They are not nutrition specific and can be challenging to transport.

Fertilizers and Soil Pollution

• Although fertilizers are primarily used to repair deficiencies in soil nutrients such as potassium, calcium, nitrogen, and sulphur, among other key macronutrients, they should be treated with the appropriate fertilizer and in the appropriate amount.
• Fertilizers are used carelessly by some farmers, resulting in soil pollution.
• Furthermore, the materials utilized in fertilizer production contain harmful substances that contribute to soil toxicity.
• For example, the rock phosphate mineral used to make mixed fertilizers contains traces of Asbestos, Cadmium, and Lead, which are transferred to the fertilizer throughout the manufacturing process.
• These metals are non-biodegradable and build up to dangerous quantities over time.

Impact of Fertilizers as Pollutants

1. Degradation of Soil Quality

• Fertilizers pollute soil due to waste material released from raw materials used in manufacturing processes.
• Because metals are not biodegradable, they can contaminate soil by accumulating in it as a result of excessive phosphate fertiliser use.
• Because of the overuse of NPK fertilisers, agricultural practises have been reduced. Wheat, maize, and gram grown in such soils have lower protein content.
• Furthermore, the carbohydrate content of such crops degrades in quality.
• When there is an excess of potassium in the soil, the vitamin C and carotene content of vegetables and fruits decreases.
• Excessive fertiliser use can alter soil fertility and acidity levels. This is why soil should be tested at least once every three years to determine the exact amount of fertiliser to be used.
• The loss of humus reduces the soil's ability to store nutrients.

2. Change in Biology of Water Bodies

• Eutrophication is caused by the overuse of fertilisers. Fertilizers contain chemicals such as NO3 and PO4, which are washed into lakes and oceans.
• These substances are toxic to aquatic life because they promote the growth of algae in bodies of water and reduce oxygen levels.
• This results in a toxic environment and the extinction of aquatic life as well as other aquatic animals and plants.
• It indirectly disrupts the food chain because different types of fish in water bodies are the primary food source for many birds and animals in the environment.

3. Effects on Human Health

• Fertilizers, which contain N2 and other chemicals, have an impact on ground water systems and are used for drinking.
• One of the most common outcomes is the development of blue baby syndrome, which occurs in infants whose skin tissues are low in oxygen, causing their skin to appear purplish or blue in colour.
• Various studies have revealed that the use of lawn fertilisers and pesticides can endanger one's health. Cancer and chronic diseases in humans, particularly in children, are examples of these risks.

4. Climate Change

• Fertilizers contain substances and chemicals such as methane, carbon dioxide, ammonia, and nitrogen, and the emission of these gases contributes to the presence of greenhouse gases in the environment.
• As a result, global warming and weather changes occur.
• Carbon dioxide, methane, and nitrous oxide are the three most significant greenhouse gases. Nitrous oxide is a nitrogen byproduct.

Prevention and Control of Fertilizers

• Both inorganic and organic fertilisers should be used sparingly for healthy soil.
• Aside from that, the soil should be allowed to replenish its nutrients naturally by resting from crop production, and fertilisers should be avoided during precipitation.
• Planting crops like corn, tobacco, and cotton on the same land for several years in a row can deplete nutrients (especially nitrogen) in the top soil. Crop rotation is one method for reducing these losses.
• Farmers plant nutrient-depleting crops in areas or strips one year. The following year, they plant legumes with nitrogen-fixing root nodules in these areas. Furthermore, by keeping the soil covered with vegetation, this method reduces erosion.
• Furthermore, the use of 'green manure' is recommended.

Manures and Soil Pollution

• Manure has long been used in farms and kitchen gardens since it is considered organic and something that people believe is great for food production due to the concept that "it originates from nature and returns to nature."
• However, according to research produced by the United Nations Food and Agriculture Organization (FAO), livestock manure is the second most common source of soil pollution.
• Despite their potential agricultural benefits, there is enough scientific evidence that manure contains growing amounts of heavy metals, pathogen organisms, and veterinary antibiotic residues, which may lead to the expansion of antimicrobial-resistant bacteria in soils.

Impact of Manure as Pollutants

• Nitrate levels in the manure above a certain threshold can be hazardous to cattle and humans.
• In some cases, high nitrate concentrations have been created by stored or land-applied manures or nitrogen fertilizers.
• Nitrogen that is not utilized for crop or plant growth can quickly reach the groundwater because nitrates freely leach down through the soil profile.
• They ultimately pollute the soil apart from other implications.
• Untreated manure is a major source of veterinary antibiotics, which can lead to an increase in antibiotic resistance in soils.

Conclusion

In some way or the other, all living beings are vulnerable to the extensive long-term use of chemicals in agriculture, such as fertilizers, manures, and other chemicals. If fertilizers and animal manures are effectively managed, they can enhance crop yield. Thus it is imperative for the applicant to be informed of the potential harmful repercussions of improper fertilizer and manure management. While we cannot completely eliminate the negative consequences of chemical fertilizers and manures, we can significantly lessen their impact by reducing their use.

FAQs

Question 1: What are fertilizers and manures?

Question 2: How do fertilizers contribute to soil pollution?

Question 3: What are the types of fertilizers?

Question 4: How do manures help in soil improvement?

Question 5: What are the environmental effects of using fertilizers and manures?

MCQs

1. Which of the following is a primary constituent of fertilizers?

A) Nitrogen

B) Carbon

C) Hydrogen

D) Oxygen

2. Which manure is derived from the excreta of animals?

A) Compost manure

B) Green manure

C) Farmyard manure

D) Chemical manure

3. What is a consequence of excessive use of chemical fertilizers?

A) Soil erosion

B) Soil fertility improvement

C) Soil pollution

D) Increased biodiversity

4. What is the effect of manures on soil texture?

A) Reduces soil porosity

B) Improves soil structure and porosity

C) Increases soil acidity

D) Decreases soil water retention

5. Which of the following is an example of an inorganic fertilizer?

A) Cattle dung

B) Compost

C) Urea

D) Green manure

GS Mains Questions and Model Answers

Q1: Explain the impact of fertilizers and manures on soil pollution and how it affects agricultural productivity.

Answer: The excessive use of fertilizers and manures can lead to soil pollution, which negatively impacts soil health and agricultural productivity. Fertilizers, particularly chemical ones, when over-applied, can lead to nutrient imbalances and accumulation of harmful metals like cadmium and lead in the soil. This contamination reduces soil fertility and disrupts the natural microbial ecosystem. Additionally, excessive fertilizers can lead to water pollution through runoff, affecting nearby water bodies. On the other hand, while manures are organic and contribute positively to soil health, their overuse can also lead to nutrient overload, affecting plant growth and soil structure. Proper management and balanced use of both fertilizers and manures are crucial to sustaining long-term agricultural productivity.

Q2: Discuss the role of organic manures in sustainable farming practices.

Answer: Organic manures such as farmyard manure, compost, and green manure play a significant role in sustainable farming by improving soil fertility without harming the environment. Unlike chemical fertilizers, organic manures are rich in organic matter, which enhances the soil’s water retention, nutrient content, and microbial activity. These manures help in maintaining soil structure and reduce the need for synthetic fertilizers. They also promote sustainable farming practices by decreasing the reliance on chemical inputs, which can lead to soil degradation and pollution. Furthermore, organic manures are a renewable resource, supporting ecological balance and ensuring long-term soil health and productivity.

Q3: Evaluate the effectiveness of current measures to control soil pollution caused by fertilizers and manures.

Answer: The current measures to control soil pollution caused by fertilizers and manures include promoting integrated nutrient management (INM), which balances the use of organic and inorganic inputs. Soil testing is encouraged to determine the exact nutrient requirements, thus minimizing overuse of fertilizers. Additionally, the use of organic farming techniques and bio-fertilizers is being promoted to reduce dependency on chemical fertilizers. Regulations such as the Fertilizer Control Order (FCO) and National Mission on Sustainable Agriculture (NMSA) aim to ensure the safe and efficient use of fertilizers. However, challenges remain in widespread implementation, particularly in rural areas, where traditional farming practices dominate. More public awareness and government incentives are required to achieve long-term reduction in soil pollution from fertilizers and manures.

Previous Year Questions on Fertilizers and Soil Pollution

1. UPSC CSE 2020

Question: "How does the excessive use of fertilizers and manures contribute to soil pollution and what steps can be taken to mitigate it?"

Answer: Excessive use of fertilizers, particularly chemical ones, leads to nutrient imbalances, soil degradation, and contamination from harmful substances like lead and cadmium. Manures, while organic, can also cause nutrient overload if used in excess. To mitigate this, the government promotes integrated nutrient management (INM), proper soil testing, and the use of organic farming practices. Additionally, farmers are encouraged to reduce over-reliance on chemical fertilizers through education and awareness programs.

2. UPSC CSE 2019

Question: "Discuss the role of fertilizers and manures in soil pollution and their impact on environmental sustainability."

Answer: Fertilizers and manures, when used excessively, contribute to soil pollution by altering soil chemistry and introducing harmful substances like heavy metals. Fertilizers, particularly nitrogen-based ones, can cause nutrient imbalances, affecting plant growth and reducing soil quality. Manures, although organic, can also affect soil structure when overused. The long-term effects include reduced agricultural productivity, groundwater contamination, and loss of biodiversity. For environmental sustainability, integrated nutrient management, crop rotation, and organic farming techniques are promoted to maintain soil health and prevent pollution.