Nutrients (nitrogen and phosphate), silt, pesticides, salts, and animal wastes are the most common agricultural nonpoint source contaminants. Agricultural nonpoint sources enter surface water via direct runoff or seepage into groundwater that discharges to a surface water outlet. Soil particles are eroded as a result of various farming activities. Erosion produces sediment that can harm fish habitats and wetlands and transport excess agricultural chemicals, resulting in a contaminated runoff. This runoff, in turn, has an impact on changes in the aquatic environment, such as temperature rises and oxygen depletion. Chemical fertilisers and manure from livestock operations are the most prevalent nonpoint sources of excess nutrients in surface water. In surface water, these nutrients produce eutrophication. 

What are the agricultural sources of water pollution?

The agricultural sources of water pollution are classified into two sources i.e., Abiotic and Biotic sources. 

Abiotic Sources 

• Pesticides- Pesticides & herbicides are used to control pests that impede crop yield on agricultural land. Pesticides that remain and accumulate in soils can affect the biological processes, enhance plant uptake of the chemical, and be hazardous to soil species, resulting in soil pollution. The persistence of pesticides and herbicides is determined by the chemical, which influences adsorption dynamics and, as a result, fate & transport in the soil ecosystem. Animals that feed infected bugs and soil organisms can collect pesticides.

• Fertilisers- Fertilisers are used to supplement crops with nutrients like phosphorus, potassium, and nitrogen that enhance plant development and increase agricultural yields. While they help plants develop, they can also disturb normal nutrient & mineral biogeochemical cycles, putting human and environmental health at risk.

• Nitrogen- Plants receive nitrogen fertiliser in nitrate and ammonium, which are biologically accessible for plant absorption. This boosts crop yields and agricultural production, but it also has the potential to pollute surface and groundwater waters and harm soil health. Crops do not take up all fertiliser nutrients, and the rest accumulates in the soil or is lost by runoff. Because of its high solubility and similar charges between molecules and negatively charged clay particles, nitrate fertilisers are considerably more likely to disappear from the soil profile through runoff. High nitrogen-containing fertiliser application rates combined with nitrate’s high water solubility result in higher runoff into surface water and leaking into groundwater, resulting in groundwater pollution.

• Phosphorus- Phosphate is the most prevalent type of phosphorus fertiliser used in agricultural activities, and it comes in synthetic compounds with PO43- or organic forms like dung and compost. As it plays a role in cell and metabolic operations, including nucleic acid synthesis and metabolic energy exchanges, phosphorus is a crucial nutrient in all organisms. Most organisms, especially crops, require only a little quantity of phosphorus since they are developed in habitats with low phosphorus levels. Organic forms of phosphorus can be converted to soluble plant-available forms such as phosphate by microbial communities in soils.

Biotic Sources

Following are the biotic sources of water pollution:

• Biopesticides- Pesticides made from natural ingredients are known as biopesticides (plants, microorganisms, animals, certain minerals). As an alternative to standard pesticides, biopesticides can help minimise overall agricultural pollution since they are easy to use, have a short residual time, and are generally non-toxic to useful invertebrates and vertebrates. However, there are worries that biopesticides may deleteriously impact non target species populations.

• Greenhouse gases from faecal waste– According to the United Nations Food and Agriculture Organisation (FAO), livestock accounts for 18% of anthropogenic greenhouse gas emissions, either directly or indirectly. This report also claimed that livestock emissions were higher than those of the transportation industry. While cattle contribute to greenhouse gas emissions, the figures have been claimed to be inaccurate. While the FAO employed a life-cycle assessment for animal agriculture (which included all factors such as emissions from growing crops for feed, transport to slaughter, and so on), they did not do so for transportation.

Effect of water pollution on agriculture

Following are the effects of water pollution on agriculture:

• Health Disorders- Agricultural contamination is the leading cause of water and lake pollution. Fertilizers and pesticides leach into the groundwater, eventually ending up in our drinking water. It may create health difficulties because it contributes to the blue baby syndrome, which causes newborn death. When oil, degreasing chemicals, metals, and poisons from farm equipment contaminate drinking water, they cause health problems.

• Impact on aquatic habits– When fertilisers, waste, ammonia, and manure are washed into neighbouring water bodies, they convert to nitrate and phosphates, which increases algae formation and decreases the oxygen in the water, resulting in the death of many aquatic species. Bacteria and parasites from animal faeces can also end up in drinking water, posing significant health risks to various marine life and animals. As a result, oxygen levels are likely to drop, perhaps resulting in the death of fish and other aquatic species.

• Eutrophication- Eutrophication is the heavy growth of plant life and algae on the water’s surface, resulting in frequent algal blooms. Excessive use of fertilisers and pesticides causes phosphorus, nitrogen, and other chemical nutrients to be carried into surrounding surface waterways by rain or irrigation, causing eutrophication of rivers and lakes by encouraging algal growth. Eutrophication causes a significant reduction in the amount of oxygen dissolved in water, which can have a negative impact on aquatic life.

• Reduce crop yield- Excessive fertiliser and pesticide use, in combination with other agrochemicals, controls weeds, invasive pests, and illnesses while yielding huge crop yields. However, the beneficial effects of these compounds are only temporary, as excessive usage of dangerous chemical elements is likely to harm the soil in the long run.

Conclusion

In the above article, we have read about agricultural sources of water pollution, types of agricultural pollution, and the effects of water pollution on agriculture. Agriculture pollution is one of the major concerns in today’s world. Nutrients (nitrogen and phosphate), silt, pesticides, animal wastes, and salts are the most common agricultural nonpoint source contaminants. Agricultural nonpoint sources enter surface water via direct runoff or seepage into groundwater that discharges to a surface water outlet. Soil particles are eroded as a result of various farming activities.