Target Grade Level / Age Range:

Grades 9-12


50 minutes


Students will understand that nitrogen is essential to plant growth and health. Students will understand how excess nitrogen in soil can cause problems in the environment.


  • Paper
  • Pens or pencils

Suggested Companion Resources (books and websites)

Vocabulary (with definitions)

  • Nitrogen fixing bacteria: bacteria that live in nodules on the roots of legumes
  • Legumes: a crop of the family Fabaceae known for their symbiotic relationship with nitrogen fixing bacteria. Common legume crops are alfalfa, clover, peas, beans, lentils, lupin, soybeans, and peanuts.
  • Eutrophication: excess nutrients stimulate plant growth (algal bloom); when plants die, decomposers use up the available oxygen during decomposition leading to hypoxia.
  • Hypoxia: oxygen is not available for other living organism creating a ‘dead zone’
  • Nitrogen cycle: bacteria (nitrosomonas) oxidize ammonia (NH 3) to nitrite (NO 2). Bacteria (nitrobacter) oxidize nitrite to nitrate (NO 3). In the final stage, anaerobic bacteria convert nitrates into nontoxic nitrogen gas
  • Methemoglobinemia: A disease in which hemoglobin cannot carry oxygen to cells throughout the body. Sometimes caused by high levels of nitrates in the human body. In infants is known as blue baby syndrome.

Background – Agricultural Connections (what would a teacher need to know to be able to teach this content)

Because amino acids build proteins and nitrogen is an essential component of amino and nucleic acids, nitrogen is vital to all life. The nitrogen cycle is complex because nitrogen can exist in multiple forms – solid or gaseous. Nitrogen is found naturally in Earth’s atmosphere and makes up approximately 78% of the air we breathe. Plants cannot use the nitrogen gas to create organic compounds for themselves. Gaseous nitrogen in the atmosphere is N 2, which is two nitrogen atoms held together by a very stable triple bond. Nitrogen gas must be changed into nitrates which plants can absorb through their roots.

Interest Approach or Motivator

  1. How has land use changed over time in Iowa? Have students brainstorm what Iowa was like in the early 1800s. How does that compare with the way land in Iowa is used today? Capture student answers up on the board or writing surface. Once answers are shared, show slide #2 in the PowerPoint. Did the student answers align with the map?
  2. Continue the student conversation by asking, ‘What is nitrogen?’ and ‘Why do plants need it?’ Have students discuss in partners and then come together as a full class to discuss. Present the information on slides #3 and #4. Have students capture key information into their notebooks.
  3. Why do plants need it?
    1. Macronutrient – plants need large amounts of it to sustain basic metabolic functions
    2. Plants have 1-6% of nitrogen by weight
    3. Building block for structure and function
    4. Essential to produce amino acids which then produce proteins
    5. Functional group on enzymes allowing them to complete specific reactions
    6. Building block of nucleic acids that make up DNA and RNA
    7. Nitrogen is in the center of the chlorophyll molecule which allows plants to photosynthesize
    8. Nitrogen uses carbohydrates giving the plant structure
    9. Nitrogen builds the protein found in grain (wheat, corn, etc.) that humans then eat
      1. Grain is graded on protein
      2. Low protein might return a low price for the grain to the farmer
  4. Nitrogen deficiencies
    1. If nitrogen resources in the soil are limited, crop growth and production becomes impaired
    2. If nitrogen in soil is low, soil amendments (fertilizers) are added to increase nitrogen levels.
    3. Plants deficient in nitrogen will show signs of yellowing
    4. Plants deficient in nitrogen will not be able to complete metabolic functions
    5. Decreased growth and vigor
  5. Crop yield and quality decreases


Objective 1: Students will understand the role that nitrogen plays in the human body, how humans get nitrogen, and what are the risks of too much nitrogen.

  1. What are natural levels of nitrogen? Break the class into four groups. Assign each group an article to read. You can print the articles off ahead of time or have the students read the articles on a computer or table. Students will read and discuss the articles in their group. Each group should prepare to teach the rest of the class about what they learned. They should prepare a 2-3 minute presentation on key facts. Give each group 8 minutes to discuss and prepare and then 2-3 minutes to present.
  2. After the student presentations, recap some of the key pieces of information. Have students capture notes into their notebook. Use slides 5-9.   Natural levels of nitrogen will be different in every field, but we can measure nitrate levels in food (per 100 gram serving)
    1. Arugula: 480 milligrams
    2. Rhubarb: 247 milligrams
    3. Butter leaf lettuce: 200 milligrams
    4. Beets: 110 milligrams
    5. Carrots: 92-195 milligrams
    6. Spinach: 24-387 milligrams
    7. Cauliflower: 20-50 milligrams
    8. Most of the nitrates in our diet come from vegetables
  3. Health benefits of nitrates in human diet
    1. Treat hypertension
    2. Treat high blood pressure
    3. Lower risk of heart disease
    4. Act as antimicrobials in the digestive system
  4. So, what’s the problem?
    1. Infants (under 6 months of age) exposed to large amounts of nitrates usually in drinking water cannot process the nitrates.
    2. This can lead to a dangerous condition called methemoglobinemia sometimes called blue baby syndrome
      1. Hemoglobin in the blood cannot carry oxygen to cells
      2. Bluish color in the skin results
      3. Severe cases can result in death
    3. This can result when nitrates are more than 10 parts per million in water
    4. 278 cases in 1940s and 1950s. Only two cases have been reported since the 1960s.
    5. Today, municipal water is treated to have no more than 10 parts per million of nitrates
  5. Increase production of cereal crops (corn, wheat, rice, etc.) highly correlates with increased use of nitrogen fertilizers
    1. This was known as the Green Revolution
    2. Nitrogen not used by plants stays in the soil, is converted to gas through denitrification, or leaches into waterways
    3. Sources of added nitrogen include:
      1. Organic sources: legumes, poultry or cow manure (only 50-70% is plant available)
      2. Inorganic sources: ammonia or urea (98% is plant available)

Objective 2: Students will understand agriculture’s role in nitrate leaching and minimizing or eliminating nitrate leaching into drinking and surface water.

  1. Present the content in slides 10-12. Have students capture information into their notebooks. Causes of nitrogen runoff
    1. Nitrate is soluble in water
    2. Nitrate is negatively charged and doesn’t have an ion bond with soil particles
    3. If water supply is too high, nitrate stays in solution and can leach out of soil or drain out through tile lines
    4. Leaching can increase
      1. from high rates of nitrogen fertilizers applied
      2. fertilizing during rainy seasons
      3. low nitrogen uptake by the crop
      4. Coarse soil textures.
  2. Problems of excess nitrogen or nitrogen runoff
    1. Algae bloom – dead zones depleting dissolved oxygen in bodies of water leading to hypoxia
    2. Contamination of drinking water: human health concerns (blue baby syndrome)
    3. Applied ammonium can reduce soil pH and lower soil quality
  3. Solutions to nitrogen runoff
    1. Nutrient management
      1. Right Source: Apply the right nutrients based on what the crop needs to grow
        1. Manure and other organic matter
        2. Inorganic nitrogen like anhydrous
      2. Right Time: Apply nutrients when the crop needs it – as the crop starts to grow and after it is harvested to replenish the soil
        1. Apply when temperature is below 50 degrees F to minimize leaching
        2. Apply right before peak crop maturation when plant is readily using nitrogen
      3. Right Place: Apply nutrients in the right place so more nutrients are used by the crop and less are lost to leaching
        1. Variable rate technology adjusting the rate of fertilizer application based on soil tests and soil maps of the field
        2. Manure injection to minimize smell and deliver nutrients to root zone
      4. Right Rate: Apply the correct amount of nutrients that the crop needs to grow – not too much, not too little.
        1. Variable rate technology adjusting the rate of fertilizer application based on soil tests and soil maps of the field
    2. Land management
      1. No-till farming
      2. Cover crops
      3. Terracing
      4. Tiling
      5. Bioreactors
      6. Buffer zones
      7. Riparian area management
  4. To solidify the content, have students create a nursery rhyme with the new learned information. They should use a common Mother Goose rhyme and change the lyrics to reflect key information from the lesson. You can have everyone use the same rhyme of allow students to choose their own. This works best in groups of two or three. Share one or two Mother Goose rhymes with students to get them thinking creatively. Allow five to ten minutes for inventing the new rhymes. Then give everyone an opportunity to recite their new rhymes. For example, a rhyme could look like this:

Five Little Nitrates Jumping in a Field (based on Five Little Monkeys Jumping on a Bed)

Five little nitrates jumping in a field,

One fell off from just the right source.

Corn called the farmer and the farmer said.

“No more nitrates jumping in the field!”

Four little nitrates jumping in a field,

One fell off at just the right time.

Soybean called the farmer and the farmer said,

“No more nitrates jumping in the field!”

Three little nitrates jumping in a field,

One fell off in just the right place.

Wheat called the farmer and the farmer said,

“No more nitrates jumping in the field!”

Two little nitrates jumping in a field,

One fell off in just the right rate.

Barley called the farmer and the farmer said,

“No more nitrates jumping in the field!”

One little nitrate jumping in the field,

He fell off and bumped his head,

Farmer called the Water and the Water mused,

“Put those nitrates straight to use!”

Essential Files (maps, charts, pictures, or documents)

Did you know? (Ag facts)

  • In considering the many transformations and reactions of N in soils, there are some major points to keep in mind. Although N can be added to soil in either organic or inorganic forms, plants take up only inorganic N (that is NO 3 --N and NH 4 +-N). One form is not more important than the other and all sources of N can be converted to NO 3 --N. 
  • Commercial N fertilizers, legumes, manures, and crop residues are all initial sources of NO 3 --N and NH 4 +-N and once in the plant or in the water supply it is impossible to identify the initial source.
  • Nitrate is always present in the soil solution and will move with the soil water.
  • Inhibiting the conversion of NH 4 +-N to NO 3 --N can result in less N loss and more plant uptake; however, it is not possible to totally prevent the movement of some NO 3 --N to water supplies, but sound management practices can keep losses within acceptable limits.

Extension Activities (how students can carry this beyond the classroom)

  • Have students research soil mapping to try and find nutrient maps from farmers in their area.
  • Have students research public health records to see if there have been any cases of methemoglobinemia that are attributed to nitrates in drinking water in the U.S. or around the world.
  • Have students write a paper on a nutrient management plan for a farm that includes right source, right rate, rate time, and right place of nutrient application.


  • Some components adapted from:
  • Adapted from: UCAR “Nitrogen Cycle Game”
  • Lesson plan development was funded by the Resource Enhancement and Protection Conservation Education Program (REAP CEP). Resource Enhancement and Protection Program (REAP): Invest in Iowa our outdoors, our heritage, our people. REAP is supported by the state of Iowa, providing funding to public and private partners for natural and cultural resources projects, including water quality, wildlife habitat, soil conservation, parks, trails, historic preservation and more.

Author(s) (your name)

Will Fett

Organization Affiliation (your organization)

Iowa Agriculture Literacy Foundation

National Agriculture Literacy Outcomes

  • T1.9-12.a. Describe how wildlife habitats are created and maintained by farmers/ranchers and why these habitats are important (e.g., promoting pollinator habitat, insect refuges, creating buffer zones for nutrient management, etc.)
  • T1-.9-12.b. Describe resource and conservation management practices used in agricultural systems (e.g., riparian management, rotational grazing, no till farming, crop and variety selection, wildlife management, timber harvesting techniques)
  • T4.9-12.c. Discuss population growth and the benefits and concerns related to science and technologies applied in agriculture to increase yields and maintain sustainability
  • T1.9-12-f. Evaluate the various definitions of “sustainable agriculture,” considering population growth, carbon footprint, environmental systems, land and water resources, and economics

Iowa Core Standards

  • HS-LS2-1. Use mathematical and/or computational representations to support explanations of factors that affect carrying capacity of ecosystems at different scales. (field carrying capacity of water, nitrogen, plants)
  • HS-ESS3-2. Evaluate competing design solutions for developing, managing, and utilizing energy and mineral resources based on cost-benefit ratios. * (adding nitrogen vs. crop rotation)
  • HS-ETS1-1. Analyze a major global challenge to specify qualitative and quantitative criteria and constraints for solutions that account for societal needs and wants. (want clean water, want abundant food, want to protect the environment)

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