Abstract
Fertilizers are added to crops in order to produce enough food to feed the human population. Fertilizers provide crops with nutrients like potassium, phosphorus, and nitrogen, which allow crops to grow bigger, faster, and to produce more food. Nitrogen in particular is an essential nutrient for the growth of every organism on Earth. Nitrogen is all around us and makes up about 78% of the air you breathe. However, plants and animals cannot use the nitrogen gas in the air. To grow, plants require nitrogen compounds from the soil, which can be produced naturally or be provided by fertilizers. However, applying excessive amounts of fertilizer leads to the release of harmful greenhouse gases into the atmosphere and the eutrophication of our waterways. Scientists are currently trying to find solutions to reduce the environmentally harmful effects of fertilizers, without reducing the amount of food we can produce when using them.
What Is Fertilizer?
Fertilizer is any substance or material added to soil that promotes plant growth. There are many fertilizer varieties, and most contain nitrogen (N), phosphorus (P), and potassium (K). In fact, fertilizers sold in stores have an N-P-K ratio on their packaging. Fertilizers are applied all around the world to keep lawns green and to produce more crops in agricultural fields. Fertilizers can be divided into three groups:
- Mineral fertilizers(phosphorus and potash) are mined from the environment and crushed or chemically treated before being applied.
- Organic fertilizers(manure and compost) are made from animal feces, and plant or animal decomposed matter.
- Industrial fertilizers(ammonium phosphate, urea, ammonium nitrate) are produced industrially by humans through chemical reactions.
While organic and mineral fertilizers have been used to increase crop yields in agriculture for a long time, industrial fertilizers are a relatively new development. Even so, industrial fertilizers are the most widely used fertilizers today.
Why Do We Need Nitrogen-Containing Fertilizers?
Nitrogen is one of the elements, or nutrients, that all living things (microorganisms, plants, and animals) need to grow. Although, there is a lot of nitrogen all around us (~78% of the air we breathe), most of the nitrogen on Earth is present as a colorless and odorless gas, called nitrogen gas (N2). Unfortunately, plants and animals cannot directly use nitrogen gas. As humans, we get our nitrogen from the food we eat. High protein foods like meat, fish, nuts, or beans are high in nitrogen. Plants get their nitrogen from the soil and nitrogen is the most common nutrient to limit plant growth. There are two ways nitrogen gas is naturally transformed or “fixed” into nitrogen-containing compounds that can end up in soil, without human intervention (Figure 1):
- Lightning: Lightning strikes generate enough energy to split nitrogen gas in the atmosphere creating nitrogen-containing compounds, which end up in soil.
- Biological nitrogen fixation: Some microorganisms can use nitrogen gas directly as a nutrient. These specialized microorganisms convert nitrogen gas to ammonium (NH4+) and are called “nitrogen fixers.” Some nitrogen-fixing microorganisms live in soil, and some can form a close relationship with the roots of certain plants, like beans or clover.
However, even with all this naturalnitrogen fixation, low nitrogen levels in soils often still limit plant growth. This is why most fertilizers contain nitrogen compounds and why industrial fertilizers are essential in order to produce enough crops to feed the human population. Humans now add as much or more industrially fixed nitrogen (~150 billion kilograms) to the environment each year, than is naturally fixed [1,2]. One hundred and fifty billion kilograms (~330 billion pounds) of anything is hard to imagine, but this is equal to the weight of ~24 million fully grown adult elephants!
How Are Nitrogen-Containing Industrial Fertilizers Produced?
As mentioned, most nitrogen on Earth is present as nitrogen gas, which is unusable for plants and animals. In the early 1900’s, scientists discovered how to transform nitrogen gas from the atmosphere into nitrogen-containing compounds that could be used to fertilize soils (Figure 1). This industrial fixation is called theHaber-Bosch process. Almost all the nitrogen in industrial fertilizers is fixed through the Haber-Bosch process.
This industrial fixation of nitrogen is performed in chemical laboratories and large factories all over the world. The Haber-Bosch process requires that nitrogen gas be mixed with hydrogen gas (H2) and put under enormous pressure (200 times atmospheric pressure). This is the pressure you would feel if you dove 2,000 meters (~6,500 feet) underneath the sea, which is a longer distance than 6 Eiffel Towers stacked on top of one another! This pressurized gas mixture is then heated to very high temperatures (450°C/842°F). Sustaining these high pressures and temperatures requires a huge amount of energy. The Haber-Bosch process is estimated to consume 1–2% of the world’s energy supply each year [2].
Why Do We Use So Much Nitrogen-Containing Industrial Fertilizer?
The short answer is that nitrogen-containing fertilizers help crop plants grow faster and helps to produce more crops. This allows agricultural land to be used more efficiently because fertilized land produces more food. In fact, the invention of industrial fertilizers is one of the main reasons the Earth’s population has grown so quickly in the last 60–70 years. Before the widespread use of industrial fertilizers in the 1960’s, it took ~123 years for the Earth’s population to double from 1 to 2 billion (1804–1927). However, it only took ~45 years (1974–2019) for the Earth’s population to double from 4 to 8 billion. Now, we are so dependent on nitrogen fertilization that we would only be able to produce enough food to feed ~50% of the world’s population without it [1,2].
Where Does the Nitrogen From Nitrogen-Containing Fertilizer End Up?
The crops take it up of course! Unfortunately, that is not the end of the story. For a more detailed look at all the reactions in the nitrogen cycle, you should read thisYoung Minds Article: “What is the Nitrogen Cycle and Why is it Key to Life” [3]. In an average agricultural field, only ~50% of the nitrogen from fertilizers is used by crops [4]. So, while fertilizers make crops grow better and faster, half of the fixed nitrogen we add is lost. Imagine that—we lose the equivalent of 12 million nitrogen elephants (~165 billion pounds) every year! The lost nitrogen can end up in the atmosphere or it can be washed out of the soil and end up in waterways, such as groundwater, streams, lakes, rivers, and oceans (Figure 2). This lost nitrogen causes a variety of environmental problems [2].
What Environmental Problems Do Nitrogen-Containing Fertilizers Cause?
Some soil microorganisms can transform nitrogen provided in fertilizers into nitrogen-containing gases, which get released into the atmosphere like the greenhouse gas nitrous oxide (N2O).Greenhouse gasesare one of the main factors accelerating global warming. Nitrous oxide has a warming potential ~300 times greater than the most commonly mentioned greenhouse gas, carbon dioxide (CO2).
In waterways, the addition of external nutrients (like excess nitrogen) is calledeutrophication. Eutrophication is an unwanted fertilization of a waterway and it promotes the growth of microorganisms, algae, and plants, just like the fertilization of soil. However, the fast growth of microorganisms and plants can use up all the oxygen in these waterways and turn them into so-called dead zones, because aquatic animals cannot live without oxygen. Eutrophication can also lead to the growth of algal species that produce toxic chemicals, calledharmful algal blooms.
While we need nitrogen from fertilizers in our agricultural soils, we do not need or want additional nitrogen in our atmosphere or waterways. This means we have to balance the positive benefits of nitrogen fertilization (more food) with the negative consequences of excess fertilizer (environmental problems) [1,2]. Scientists are currently working to find this balance to improve our current situation.
What Fertilizer Related Research Is Currently Being Done?
One main goal of fertilizer related research is to decrease the amount of industrially fixed nitrogen that is lost (~12 million elephants worth) to the atmosphere and waterways. This solution is called improving the nitrogen use efficiency of agricultural environments. Here are a few examples of ongoing fertilizer research:
Microbiologistsandsoil scientistsare working on ways to improve field conditions to promote the growth of naturally occurring soil nitrogen-fixing bacteria. In addition, they are also working on ways to prevent the growth of soil microorganisms that contribute to fixed nitrogen being lost to the atmosphere or waterways (Figure 3). Together, this would reduce the overall amount of nitrogen-containing fertilizer needed to get the same crop yield.
Chemistsare working on designing fertilizers that are stable in soils over longer time periods and are less likely to be broken down by microorganisms. These slow release fertilizers release little bits of nutrients at a time, so nutrients are available throughout the lifetime of the crops. This approach is still dependent on nitrogen-containing fertilizers, but it would reduce the amount of fertilizer needed and decrease the nitrogen lost.
Plant biologistsare trying to genetically engineer crops that would require less nitrogen from fertilizers [5]. These crops would be able to fix their own nitrogen from nitrogen gas, just like the specialized nitrogen-fixing microorganisms. These crops would need less fertilizer to produce the same crop yield (Figure 3).
Computer scientistsandsoil scientistsare working together to design smart fertilization systems, which can monitor soil and air conditions in agricultural fields. These systems can then add small amounts of fertilizer only when needed. This minimizes the amount of fertilizer added, makes fertilizer additions targeted to the crops needs, and decreases the amount of nitrogen lost.
Summary
Fertilizers provide crops with essential nutrients like nitrogen, so that the crops grow bigger, faster, and produce more food. However, applying too much fertilizer can be a problem because it leads to the release of greenhouse gases and eutrophication. Scientists are currently trying to find solutions to reduce the amount of fertilizers needed, without reducing the amount of food produced.
Glossary
Nitrogen Fixation:↑The process of converting nitrogen gas into nitrogen containing compounds. Nitrogen fixation can occur naturally through lightning strikes, be performed by specialized microorganisms, or be accomplished industrially.
Haber-Bosch Process:↑An industrial nitrogen fixation process that can be performed in a laboratory to produce fertilizer components. It was discovered by and is named for the scientists Fritz Haber and Carl Bosch.
Greenhouse Gases:↑Gases that trap heat in the atmosphere much like the roof of a greenhouse traps heat to protect the plants growing in it from cold weather and frost.
Eutrophication:↑A change in an environment’s nutrient status caused by high levels of nutrients (nitrogen or phosphorus) entering waterways (lakes, rivers, or oceans). One major consequence is harmful algal blooms and the loss of aquatic life.
Harmful Algal Blooms:↑When cyanobacteria and algae grow very fast because of large amounts of nutrients (nitrogen or phosphorus) present in the waters they live in. These cyanobacteria and algae release harmful chemicals—toxins—into the waterway.
Conflict of Interest
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Acknowledgments
Linnea Kop graciously created and granted permission for the use of her illustrations for all of the figures used in this article.
References
[1]↑Galloway, J. N., Leach, A. M., Erisman, J. W., and Bleeker, A. 2017. Nitrogen: the historical progression from ignorance to knowledge, with a view to future solutions.Soil Res.55:417–24. doi: 10.1071/SR16334
[2]↑Erisman, J. W., Galloway, J. N., Dice, N. B., Sutton, M. A., Bleeker, A., Grizzetti, B., et al. 2015.Nitrogen: Too Much of a Vital Resource. Science Brief. Zeist: WWF Netherlands.
[3]↑Aczel, M. 2019. What is the nitrogen cycle and why is it key to life?Front. Young Minds7:41. doi: 10.3389/frym.2019.00041
[4]↑Hirel, B., Tétu, T., Lea, P. J., and Dubois, F. 2011. Improving nitrogen use efficiency in crops for sustainable agriculture.Sustainability3:1452–85. doi: 10.3390/su3091452
[5]↑Good, A., 2018. Toward nitrogen-fixing plants: a concerted research effort could yield engineered plants that can directly fix nitrogen.Science359:869–70. doi: 10.1126/science.aas8737
FAQs
Is Too Much Fertilizer a Problem? ›
Too much fertilizer (applied too often or too much) can burn or desiccate roots, ultimately killing the plant. Too much fertilizer can also be harmful to the environment. But, fertilizers do a lot of good by providing macro and micronutrients that enhance the health and performance of plants.
Is too much fertilizer is bad for an ecosystem? ›Too much fertilizer can actually kill the plant and excess fertilizer can runoff into streams and lakes causing toxic algal blooms that are harmful to aquatic life and even people and their pets. Excess fertilizer runoff from lawns and agricultural applications also contribute to aquatic “dead zones” in coastal areas.
What are 3 consequences of over fertilizing? ›Over fertilization can actually decrease growth and leave plants weak and vulnerable to pests and diseases. It can also lead to the ultimate demise of the plant. Signs of over fertilization include stunted growth, burned or dried leaf margins, wilting, and collapse or death of plants.
What happens when there is overuse of fertilizers? ›Excess use of fertilizers causes environmental pollution as their residual and unused amounts will become pollutants for air, water, and soil. It also initiates the process of eutrophication in the water bodies, decreasing the soil quality by killing the soil microflora, etc.
What is one problem with fertilizer? ›Some of these impacts include algae blooms causing the depletion of oxygen in surface waters, pathogens and nitrates in drinking water, and the emission of odors and gases into the air. Nutrients from manure and fertilizers enter lakes and streams through runoff and soil erosion.
Are fertilizers too much of a good thing? ›Excess fertilizer alters the soil by creating too high of a salt concentration, and this can hurt beneficial soil microorganisms. Over- fertilization can lead to sudden plant growth with an insufficient root system to supply adequate water and nutrients to the plant.
How much is too much fertilizer? ›To avoid over-fertilizing, applying a fertilizer every two weeks is not recommended. Fertilizing as often as every two weeks will likely lead to problems such as lawn burn, excessive grass growth, as well as polluted water that can lead to toxic algae growth.
Can plants survive over fertilizing? ›Too much fertilizer can potentially cause a chemical burn on the roots of your plant. In severe cases, it can also cause the whole plant to wilt and die. You'll need to act quickly if your plant has been overfertilized.
Does fertilizer have negative effects? ›To grow, plants require nitrogen compounds from the soil, which can be produced naturally or be provided by fertilizers. However, applying excessive amounts of fertilizer leads to the release of harmful greenhouse gases into the atmosphere and the eutrophication of our waterways.
What results from excessive use of fertilizers is called? ›Nutrient pollution is the process where too many nutrients, mainly nitrogen and phosphorus, are added to bodies of water and can act like fertilizer, causing excessive growth of algae. Nutrients can run off of land in urban areas where lawn and garden fertilizers are used.
Will grass grow back after fertilizer burn? ›
Fertilizer burnt grass can grow back if untreated, but this is not likely the case. Most of the time, you will have to apply some extra water to the turf to ensure the burn goes away.
How do you reverse the effects of too much fertilizer? ›Giving your lawn extra water helps to dilute and wash away the excess fertilizer. This remedy works best if done promptly after over-fertilizing but even if you already notice some browning or yellowing of the grass, water helps it to recover and bounce back.
What are two disadvantages of fertilizer? ›- The naturally occurring microorganisms in soil are harmed by the chemicals in the fertilizers.
- It can destroy the soil fertility of an area.
- It can reduce the organic matter and humus content in the soil.
Fertilizer replaces the nutrients we take from the soil when we harvest a crop. If we don't replace the nutrients, the soil slowly gets mined to exhaustion.
What are 4 effects of fertilizer? ›Fertilizers boost crop yields, but their excessive usage has hardened the soil, reduced fertility, strengthened insecticides, polluted air and water, and emitted greenhouse gases, creating health and environmental risks.
How does too much fertilizer affect soil? ›However, excessive use of chemical fertilizers has led to several issues such as serious soil degradation, nitrogen leaching, soil compaction, reduction in soil organic matter, and loss of soil carbon.
Why do we need so much fertilizer? ›Without fertilizers, nature struggles to replenish the nutrients in the soil. When crops are harvested, important nutrients are removed from the soil, because they follow the crop and end up at the dinner table. If the soil is not replenished with nutrients through fertilizing, crop yields will deteriorate over time.
Is fertilizing your lawn bad for the environment? ›Overapplication of any lawn chemical can result in runoff that carries toxic levels of chemicals or excessive nutrients into lakes, streams and groundwater. Fertilizers usually contain nitrogen, phosphorous and potassium (potash). Nitrogen is an important lawn nutrient, but it can contaminate groundwater with nitrates.
Can you over fertilize with nitrogen? ›The same nutrients that make your lawn green and healthy -- nitrogen, phosphorus, and potassium -- can hurt your lawn if you apply too much. Too much fertilizer adds too much nitrogen and salt to the soil. It's called fertilizer “burn,” and can actually kill your lawn.
What is a normal amount of fertilizer? ›In general, lawns should be fertilized about 4 times a year with 1 lb. of nitrogen at each application. Both cool-season and warm-season grasses require 4 - 6 lbs. of actual nitrogen per year. This amount is usually divided into 4 applications of 0.5 to 1 lb.
How many times a year should you fertilize your lawn? ›
A well-fed lawn is healthier, which means it has a better root system to combat heat, cold, drought, mowing, foot traffic, and other stresses. While feeding your lawn once a year will improve its condition, feeding it 4 times a year will make it even healthier and more beautiful.
When should you not fertilize? ›Applying fertilizer in the wrong season can cause increased tender new growth that can be damaged, especially if applied in cold weather in late fall or in winter. So it is best to stop fertilizing during dormant seasons. Additionally, in zones that can be in danger of a late freeze, it's best to wait until mid-spring.
How many times can I fertilize my plants? ›Vegetable gardeners can fertilize their garden beds about once a month with a quick-release fertilizer or about once a season with a slow-release fertilizer. Some gardeners prefer to feed their flowers and plants with a liquid-soluble plant food once every one to two weeks.
What makes plants grow faster and bigger? ›So What Makes Plants Grow Faster & Bigger? Water, air, light, soil nutrients, and the correct temperature coupled with affection and care are the most basic factors to make a plant grow faster and bigger.
Which fertilizer should not be mixed? ›Don't try to mix hydrated lime or flowable dolomite with fertilizers. This can cause an excessive release of ammonia. Mixing calcium nitrate with phosphorus fertilizers can cause precipitation or “salting out” of calcium phosphate and calcium ammonium phosphate.
What happens to plants with excess nitrogen? ›Excess nitrogen can cause plants to grow excessively and develop overly succulent leaves and shoots, which promotes outbreaks of certain sucking insects and mites. Excessive nitrogen causes fruiting plants to produce relatively more foliage, reducing their fruit production and delaying fruit maturity.
Are weeds which typically live longer than a year but no longer than two years? ›Biennial weeds survive for two growing seasons, reproducing vegetatively or by seed; however, seed is not produced until the second year. Perennial weeds survive for many years, and though they produce seeds, many primarily reproduce vegetatively by creeping stems (stolons and rhizomes), tubers, or fleshy roots.
How do you fix grass that has been killed by fertilizer? ›How to Repair Burned Grass from Fertilizer. Burned lawns will need a generous amount of water to get back to green. It's important to water your lawn as soon as you spot any brown or yellow patches to prevent further damage. Slowly soak the affected areas every day for about a week to fully flush out the salt.
How long does it take for fertilizer to get out of grass? ›After the fertilizer has been completely absorbed into the soil, yes. It's generally recommended to wait about 24-72 hours after a fertilizer application before letting your kids go back onto the grass and to also ensure your lawn is watered well before the kids go back to playing in the grass.
Can I fertilize my lawn every 2 weeks? ›But even then, you should not fertilize more often then every three or four weeks. If you fertilize too often, you can damage your lawn.
How long does it take a plant to recover from fertilizer burn? ›
Be sure to remove excess fertilizer and flush out excess with water. You may even need to replant in new soil if the soil is over-saturated with fertilizers. How long it will take your plant to recover will depend on the plant. It generally takes a couple of weeks to recover.
Why is my lawn turning brown after fertilizing? ›Over-Fertilization
Many fertilizers also have soluble salts in them, and these can actually burn the grass and leave it brown. This is especially common for quick-release fertilizers. If you spilled the fertilizer or applied too much in certain areas, then you could get brown patches in your grass.
Watering to the appropriate levels after a fertilizer application is important. Too much and you can have run-off and diluted products. Too little and the fertilizer will just sit on the very surface of the ground and will not provide ideal conditions for the grass to take up the nutrients.
What are the cons of lawn fertilizer? ›- Grass burns and injury to plants.
- Polluted waterways.
- Contaminated drinking water.
- Damage to native plants and animals.
- Harm to skin and airways of humans and household pets.
Manure is the organic matter added to the soil to increase its fertility. On the contrary, fertilizers are chemicals that are added to the soil to increase its fertility. Fertilizers might harm the soil, but manure is environment-friendly.
What is one disadvantage of using organic fertilizer? ›The biggest disadvantage of using an organic fertilizer is that it may not contain primary nutrients like nitrogen, phosphorous or potassium, also known as NPK. Manure-based fertilizers contain these nutrients and are still considered organic. However, many others don't contain significant quantities of NPK.
What diseases are caused by fertilizers? ›High levels of nitrates and nitrites in chemical fertilizer may cause some disease like hemoglobin disorders, Alzheimer's disease and diabetes mellitus. As chemical fertilizers are composed chemical substances so they have lots of detrimental effects on human health as well as environment.
How do you stop fertilizer runoff? ›Plant native trees and shrubs, keep livestock away from water's edges, and leave grass or native buffers between tilled fields and streams. Leave stubble on tilled fields through the winter, cover manure piles, and plant a grass or native buffer between agriculture activities and streams.
Is fertilizer bad for wildlife? ›The chemicals that are so helpful in encouraging plant growth can be toxic for birds and other wildlife that come into the garden. If digested by birds, lawn fertilizer can cause serious harm.
How does fertilizing affect the environment? ›Excessive use of fertilizers leads to eutrophication. Fertilizers contain substances including nitrates and phosphorus that are flooded into lakes and oceans through rains and sewage. These substances boost the excessive growth of algae in the water bodies, thereby decreasing the level of oxygen for aquatic life.
How do fertilizers affect climate change? ›
Production and transportation cause carbon emissions, while agricultural use of these fertilizers leads to the release of nitrous oxide (N2O)—a greenhouse gas 265 times more potent than carbon dioxide (CO2) over a century.
Can fertilizer hurt soil? ›However, excessive use of chemical fertilizers has led to several issues such as serious soil degradation, nitrogen leaching, soil compaction, reduction in soil organic matter, and loss of soil carbon.
Will fertilizer hurt birds? ›The key to a healthy lawn is regular fertilization. However, some people are concerned that the fertilizer they spread on their lawn may have harmful effects on local wildlife, specifically birds. The good news is that lawn fertilizer generally does not hurt birds.
Will fertilizer hurt animals? ›While commercial fertilizers may provide nutrition for plants, they contain harmful chemicals which are toxic to dogs. Your dog can accidentally consume these chemicals when they are sprinkled on the lawn or garden just by running and playing outside and then grooming himself.
What kind of fertilizer is the least harmful to the environment? ›Organic Fertiliser
This includes manure, blood meal and bone meal. They are good for the soil because they are slow release, meaning you don't need to apply as much chemical fertiliser. They also do not pollute the environment like some inorganic fertilisers can do.
Early farmers used manure to fertilize their crops thousands of years ago, even before farm machinery was invented to make the task more efficient.
Why did Canada ban fertilizer? ›Canada is urging farmers to reduce fertilizer emissions to curb greenhouse gases, triggering a backlash. The government of Justin Trudeau is proposing a 30% reduction by 2030 from 2020 levels in emissions from fertilizer as part of a plan to reduce greenhouse gases.
How does fertilizer affect water? ›High levels of nitrogen and phosphorus can cause eutrophication of water bodies. Eutrophication can lead to hypoxia (“dead zones”), causing fish kills and a decrease in aquatic life.
Is breathing in fertilizer bad? ›Plant fertilizers can poison people and pets if they are inhaled or accidentally ingested. Touching the fertilizer may cause skin irritation, and ingesting it may be poisonous. Nitrates are the ingredients that cause the poisoning. Nitrates are a form of nitrogen that plants can easily absorb.
Is mowing the lawn bad for the environment? ›Maintaining grass lawns increases greenhouse gasses, pollutes ecosystems, wastes water, and diminishes biodiversity. Grass lawns are expensive, unsustainable, and poor investments. While more environmentally friendly than pavement, grass lawns and their upkeep come with heavy carbon costs.
How do fertilizers cause pollution? ›
The usage of organic fertilizers results in the discharge of nitrate, potassium and phosphates that pollute the water. The contamination of groundwater occurs as a result of leaching due to nitrate. The ground and surface waters are infested with heavy metals, whose concentration poses a threat to humans and animals.