Understanding Our Soil: The Nitrogen Cycle, Fixers, and Fertilizer

Summary

The script explores the importance of nitrogen-fixing plants like peas, beans, and clover in the soil's health. It explains how these plants, through symbiotic bacteria in their roots, convert atmospheric nitrogen into a form usable by plants, enhancing soil fertility naturally. The script contrasts this organic process with chemical fertilizers, which can disrupt soil life, pollute waterways, and contribute to climate change. It emphasizes the need for maintaining healthy soil for nutritious food production.

Takeaways

• 🌿 Peas, beans, and clover are among the 18,000 species in the pea family, known as nitrogen fixers that increase soil nitrogen levels, essential for plant growth and protein production.
• 🌱 Interplanting nitrogen-fixing plants with others that require nitrogen or planting nitrogen-fixing cover crops like clover can enrich the soil for future planting.
• 🔄 Nitrogen makes up 78% of the Earth's atmosphere but is not directly usable by plants; it must be converted by bacteria into ammonium, then nitrite, and finally nitrate, which plants can absorb.
• 🌾 Plants often rely on mycorrhizal fungi attached to their roots to bring nutrients, including nitrogen, in exchange for sugars and carbohydrates exuded by the plant roots.
• 🌱 Nitrogen in the soil can be lost through crop harvesting, water runoff, or conversion back to atmospheric nitrogen by anaerobic bacteria under oxygen-deficient conditions.
• 🌳 Nitrogen-fixing plants, such as clover, facilitate bacteria that fix nitrogen by housing them in root nodules, where the bacteria convert atmospheric nitrogen into ammonium for plant use.
• 🌊 The use of synthetic nitrogen fertilizers can lead to environmental issues, such as nutrient runoff polluting waterways and contributing to eutrophication.
• 🌍 Nitrogen fertilizers can also lead to the release of nitrous oxide, a potent greenhouse gas, and disrupt the soil ecosystem, including the death or displacement of earthworms and beneficial fungi.
• 🌱 Healthy soil is vital for growing nutritious food; nitrogen-fixing plants can help restore life to depleted or 'dead' soil, promoting a self-sustaining ecosystem.
• 💧 The loss of soil organisms due to synthetic fertilizer use means that additional mineral fertilizers are needed, further depleting the soil's natural nutrient cycle.
• 📉 The decline in soil health over the past century has corresponded with a decrease in the nutritional value of vegetables, highlighting the importance of maintaining a living, fertile soil.

Q & A

What is the significance of the pea family in the context of the soil's nitrogen level?

The pea family, including peas, beans, and clover, contains nitrogen-fixing species that are capable of increasing the soil's nitrogen level, which is essential for plant growth and protein production.

How do nitrogen-fixing plants contribute to the soil's fertility?

Nitrogen-fixing plants, such as those in the pea family, create a habitat for bacteria that fix atmospheric nitrogen into a form that plants can use. The ammonium produced by these bacteria is released into the soil, enriching it for other plants and microorganisms.

What is the role of bacteria in the nitrogen cycle?

Bacteria play a crucial role in the nitrogen cycle by converting atmospheric nitrogen into various forms such as ammonium, nitrite, and nitrate, which are then available for plants to absorb and use.

Why is it beneficial to interplant nitrogen-fixers with other plants in a garden?

Interplanting nitrogen-fixers with other plants can enhance the soil's fertility by providing a natural source of nitrogen, which is particularly beneficial for plants that require a lot of nitrogen for growth.

How do plants typically acquire the nitrogen they need for growth?

Plants usually acquire nitrogen through mycorrhizal fungi that attach to their roots, bringing nutrients to the plant in exchange for sugars and carbohydrates exuded by the plant roots.

What happens to the nitrogen in the soil when crops are harvested?

When crops are harvested, the nitrogen contained in the removed plant material is taken away from the soil, which can lead to a decrease in soil fertility.

How does the use of nitrogen fertilizers differ from nitrogen fixation by plants?

Nitrogen fertilizers provide plants with pure nitrogen without the organisms involved in the natural nitrogen cycle, which can lead to environmental issues such as water pollution and greenhouse gas emissions.

What are the environmental consequences of using nitrogen fertilizers?

The use of nitrogen fertilizers can result in water pollution due to runoff, contribute to the release of nitrous oxide—a potent greenhouse gas—and disrupt the soil ecosystem by killing beneficial organisms and altering the soil pH.

Why is it important to maintain a healthy soil ecosystem for plant growth?

A healthy soil ecosystem supports a self-sustaining web of organisms that freely share nutrients, which is essential for plant growth and maintaining the nutritional value of the food produced.

How can nitrogen-fixing plants help improve soil health?

Nitrogen-fixing plants can help improve soil health by providing a habitat for nitrogen-fixing bacteria, which enrich the soil with nitrogen and support the growth of beneficial organisms that contribute to soil fertility.

What is the impact of soil health on the nutritional value of vegetables?

Healthy soil rich in beneficial organisms and nutrients is essential for producing vegetables with high nutritional value. Declining soil health has been linked to a decrease in the nutritional value of vegetables over the last century.

Outlines

00:00

🌱 Nitrogen Fixation in Pea Family Plants

This paragraph discusses the role of nitrogen-fixing plants like peas, beans, and clover within the pea family. These plants are crucial for increasing soil nitrogen levels, which is essential for plant growth and protein synthesis. The text explains the concept of interplanting nitrogen-fixers with nitrogen-demanding plants or using cover crops like clover to enrich the soil for future use. It also raises the question of why nitrogen-fixing plants are preferred over nitrogen fertilizers, setting the stage for an explanation of the nitrogen cycle and the importance of soil bacteria in making nitrogen available to plants.

🌿 Understanding the Nitrogen Cycle

This section delves into the nitrogen cycle, explaining how nitrogen, which makes up 78% of the Earth's atmosphere, is mostly unavailable to plants due to its unreactive diatomic form. The paragraph describes the process of nitrogen fixation by bacteria, which convert atmospheric nitrogen into ammonium, then nitrite, and finally nitrate—forms that plants can absorb. It highlights the symbiotic relationship between plants and fungi, where fungi provide nutrients to plants in exchange for sugars. The paragraph also touches on how nitrogen is lost from the soil through various means, such as harvest, water runoff, and gaseous release, and how anaerobic bacteria can convert nitrates back into atmospheric nitrogen under oxygen-deficient conditions.

🌳 The Role of Nitrogen-Fixing Plants and Bacteria

This paragraph clarifies the misconception that nitrogen-fixing plants directly fix nitrogen. Instead, they provide a habitat for nitrogen-fixing bacteria, particularly in root nodules, where these bacteria convert atmospheric nitrogen into ammonium, benefiting neighboring plants and soil microorganisms. The text emphasizes the importance of these plants in maintaining soil health and the abundance of beneficial bacteria when they die and decompose, contributing to a self-sustaining ecosystem of soil life.

💧 Environmental Impact of Chemical Fertilizers

The paragraph discusses the environmental consequences of using chemical nitrogen fertilizers, which can lead to water pollution through runoff and contribute to greenhouse gas emissions through volatilization. It points out that fertilizers can disrupt soil life, including earthworms and beneficial fungi, and alter soil pH, making it less hospitable for bacteria. The reliance on fertilizers can create a cycle of soil degradation and increased fertilizer use, exacerbating environmental issues and contributing to climate change.

🌾 The Decline in Soil and Nutritional Value

This final paragraph connects the decline in soil health with the decrease in the nutritional value of vegetables over the last century. It argues that healthy food production is dependent on healthy soil and emphasizes the importance of maintaining or reviving soil life through the use of nitrogen-fixing plants. The paragraph concludes by encouraging the preservation of rich, living soil and the use of nitrogen-fixers to restore life to depleted or dying soils, highlighting the importance of soil organisms in nutrient cycling and overall ecosystem health.

Keywords

💡Nitrogen Fixers

Nitrogen fixers are plants that have a symbiotic relationship with nitrogen-fixing bacteria, which convert atmospheric nitrogen into a form that plants can use. In the script, peas, beans, and clover are mentioned as nitrogen fixers, which are crucial for increasing the nitrogen level in the soil, thus helping other plants to grow by providing them with the necessary nitrogen for protein synthesis and chlorophyll production.

💡Nitrogen Cycle

The nitrogen cycle is the process by which nitrogen is converted into various chemical forms in the environment. It is central to the script's theme as it explains how nitrogen becomes available to plants. The cycle involves bacteria that convert atmospheric nitrogen into ammonium, then into nitrite and nitrate, which plants can absorb. The script emphasizes the importance of this cycle for plant growth and soil health.

💡Ammonium

Ammonium is a form of nitrogen that is produced by nitrogen-fixing bacteria as they convert atmospheric nitrogen. It is an essential component in the nitrogen cycle and is mentioned in the script as the first step in making nitrogen available to plants. Ammonium is then further processed by other bacteria into other forms of nitrogen that plants can use.

💡Nitrite

Nitrite is another form of nitrogen in the nitrogen cycle. It is produced when ammonium is consumed by certain bacteria. The script explains that nitrite is a transitional form that is eventually converted into nitrate, which is more readily absorbed by plants.

💡Nitrate

Nitrate is the final product of the nitrogen cycle that plants can directly absorb and use for growth. The script highlights that nitrate is the most accessible form of nitrogen for plants, often facilitated by mycorrhizal fungi that form a symbiotic relationship with plant roots.

💡Mycorrhizal Fungi

Mycorrhizal fungi are symbiotic organisms that form a relationship with plant roots, aiding in the absorption of nutrients, including nitrogen, in exchange for sugars and carbohydrates from the plant. The script mentions these fungi as a critical component in the nitrogen cycle, helping plants access nitrogen from the soil.

💡Nodules

Nodules are specialized structures found on the roots of nitrogen-fixing plants, such as clover, where nitrogen-fixing bacteria reside. The script describes these nodules as housing bacteria that convert atmospheric nitrogen into ammonium, which is then released into the soil for use by other plants.

💡Eutrophication

Eutrophication is the process by which an excess of nutrients, particularly nitrogen, leads to an overgrowth of algae in water bodies. The script mentions this as a negative environmental impact of nitrogen fertilizer runoff, which disrupts aquatic ecosystems.

💡Greenhouse Gases

Greenhouse gases, such as nitrous oxide, are mentioned in the script as a byproduct of the use of nitrogen fertilizers. The script explains that the volatilization of nitrogen from fertilizers can release potent greenhouse gases into the atmosphere, contributing to climate change.

💡Soil Health

Soil health is a central theme in the script, emphasizing the importance of maintaining a living soil rich in microorganisms for plant growth. The script contrasts the use of chemical fertilizers, which can harm soil life, with the use of nitrogen-fixing plants, which promote a healthy soil ecosystem.

💡Organic Fertilization

Organic fertilization refers to the natural process of enriching soil with nutrients through the use of organic matter, such as nitrogen-fixing plants. The script promotes this method over chemical fertilizers, highlighting its benefits for soil health, plant growth, and environmental sustainability.

Highlights

Peas, beans, and clover are among the 18,000 species in the pea family known as nitrogen fixers that increase soil nitrogen levels.

Nitrogen fixers help plants produce proteins and chlorophyll for growth and photosynthesis by increasing available nitrogen in the soil.

Interplanting nitrogen fixers with nitrogen-demanding plants or planting nitrogen-fixing cover crops like clover can improve soil fertility.

Nitrogen fertilizers do not replicate the benefits of nitrogen fixation, which involves a symbiotic relationship between plants and bacteria.

Understanding nitrogen fixation requires knowledge of the broader nitrogen cycle involving various bacteria species and plant interactions.

Nitrogen makes up 78% of Earth's atmosphere but is mostly unreactive and unavailable to plants without bacterial assistance.

Bacteria convert atmospheric nitrogen into ammonium, then nitrite, and finally nitrate, which plants can absorb directly or through mycorrhizal fungi.

Plants rely on mycorrhizal fungi attached to their roots to bring nutrients in exchange for sugars and carbohydrates.

Nitrogen exits the soil through crop harvest, water runoff, or conversion back to atmospheric nitrogen by anaerobic bacteria under oxygen-deficient conditions.

Nitrogen-fixing plants like clover create a habitat for nitrogen-fixing bacteria in root nodules, benefiting neighboring plants and soil microorganisms.

When nitrogen-fixing plants die, the bacteria disperse into the soil, enriching it with beneficial bacteria for future plant growth.

Fertilizers add pure nitrogen without the beneficial organisms, leading to environmental issues like water pollution and greenhouse gas emissions.

Fertilizer runoff can disrupt aquatic ecosystems by promoting excessive algae growth due to the high nitrogen content.

Excessive nitrogen from fertilizers can lead to volatilization, releasing nitrous oxide, a potent greenhouse gas, into the atmosphere.

Fertilizers can irritate earthworms, disrupt beneficial fungi on plant roots, and alter soil pH, making it inhospitable for bacteria.

Overreliance on fertilizers can lead to a vicious cycle of soil degradation, loss of beneficial organisms, and increased fertilizer use.

Healthy soil is essential for producing nutritious food, and nitrogen-fixing plants can help restore life to depleted or dead soils.

Maintaining a diverse and active soil ecosystem is crucial for long-term agricultural sustainability and nutritional value of crops.

Transcripts

peas beans and clover are among the 18

000 species in the pea family

most species in this family including

these three are known as nitrogen fixers

they increase the level of nitrogen in

the soil which plants need to produce

proteins so they can grow

and chlorophyll so they can

photosynthesize one way to use this in

the garden is to interplant nitrogen

fixers with other plants that need a lot

of nitrogen

or you could plant a nitrogen-fixing

cover crop like clover for fertile soil

next year

okay this can be useful but doesn't

nitrogen fertilizer do the same thing

but more conveniently

why bother with this nitrogen fixation

thing

understanding this requires us to

understand how nitrogen fixation works

which in turn requires us to understand

the broader nitrogen cycle

so let's start with the big picture

nitrogen makes up 78 of the earth's

atmosphere by volume

but most of this nitrogen takes the form

of two nitrogen atoms strongly bonded

together

which isn't very reactive and is useless

to plants

for it to become plant available we need

the help of bacteria

various species of bacteria eat

atmospheric nitrogen and poop out

ammonium

this gets eaten by other kinds of

bacteria which poop out nitrite

which gets eaten by yet another kind of

bacteria which poops out nitrate

all of these forms of nitrogen are

available for plants especially nitrate

which is the easiest for plants to use

plants can take this up directly if it

is near their roots but they most often

rely on strands of fungi that attach to

their roots and bring nutrients to them

in exchange for the sugars and

carbohydrates the plant roots exude

dead plant material is also rich in

nitrogen and gets brought down with the

help of worms whose poop is a delicacy

among nitrifying bacteria

some of the ways nitrogen exits the soil

is when the crop is harvested

when water carries it away or when it

becomes gaseous and returns to the

atmosphere

or if the soil lacks oxygen different

anaerobic bacteria grow which convert

nitrates back into atmospheric nitrogen

notice that these things only happen

with loose nitrogen in the soil

not with nitrogen inside organisms

okay so we know that the nitrogen cycle

depends heavily on life in the soil

without them the plants would be quite

sad but you may have noticed

if the fixation process is done by

bacteria where do nitrogen-fixing plants

fit into this

believe it or not nitrogen-fixing plants

don't fix nitrogen

rather they create habitat for the

bacteria that do the roots of this

clover plant have little nodules that

house huge amounts of nitrogen-fixing

bacteria

the ammonium that these bacteria create

slowly releases into the soil for

neighboring plants and microorganisms to

use

when the plant dies the bacteria

disperse into the soil

resulting in an abundance of bacterial

allies for future plants nitrogen needs

you know how earlier i said that water

can carry soil nitrogen away

this nitrogen ends up in rivers which

can disrupt the ecosystem by enabling

algae to dominate

but remember this only happens to lose

nitrogen in the soil

and not nitrogen embedded in organisms

and fertilizer

adds pure nitrogen without the organisms

so when it rains

huge amounts of it runoff and pollute

the water loose nitrogen

molecules are also much more prone to

volatilization releasing huge amounts of

nitrous oxide a potent greenhouse gas

into the atmosphere but that's not all

such quantities of pure nitrogen

irritate earthworms which end up dying

or leaving

it disrupts the helpful fungus on plant

roots and changes the soil ph

making it inhospitable to bacteria in

short it kills the soil

when the nitrogen all gets used up or

washes away the organisms aren't there

to help the plants get more so now you

have to add more fertilizer which

worsens the problem

and these organisms did much more than

just supply nitrogen the root fungi also

brought up important minerals for the

plants

and now that they're gone mineral

fertilizer must also be used

instead of working with this

self-sustaining web of organisms freely

sharing nutrients

we have to spend more money to add loads

of fertilizer to dead soil

poisoning the water and contributing to

climate change considering the inability

of dead soil to supply plants with

nutrients

it's no wonder that throughout the last

century vegetables have been steadily

declining in nutritional value

healthy food requires healthy soil

so if the soil around you is rich and

alive try to keep it that way

but if like most of us the soil around

you is dead or dying

nitrogen fixers can help to add a little

more life so that someday our tiny

allies under our feet will come back

you