Biology of Soil - Lesson 12 - Future of Soil

Author

Will Fett

Published

6/8/2014

Biology of Soil - Lesson 12 - Future of Soil

Topics:

Lesson Plans - 9th - 12th

Target Grade Level / Age Range:

Grades 9-12

Estimated Time:

90 minutes

Purpose:

Students will identify the opportunities and challenges that exist with managing soils and soil biology and implementing best management practices.

Materials:

Worksheets for students
Writing utensils

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

Vocabulary (with definitions)

Carbon sequestration – a natural or artificial process by which carbon dioxide is removed from the atmosphere and held in solid or liquid form.
Climate change – a change in global or regional climate patterns, in particular a change apparent from the mid to late 20th century onwards and attributed largely to the increased levels of atmospheric carbon dioxide produced by the use of fossil fuels.
Best management practice – a practice, or combination of practices, that is determined to be an effective and practicable (including technological, economic, and institutional considerations) to achieve a desired outcome.

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

Through photosynthesis, plants absorb carbon dioxide from the atmosphere. They use water and sunlight to turn the carbon into leaves, stems, seeds and roots. As the plants respire, they return some carbon dioxide to the atmosphere and exude some carbon as a sugary substance through their roots. This secretion feeds the microbes (bacteria, fungi, protozoa and nematodes) that live underground. When the plants die, soil microbes break down their carbon compounds and use them for metabolism and growth, respiring some back to the atmosphere.

Because microbial decomposition releases carbon dioxide, the soil can store more carbon when it is protected from microbial activity. One key way that happens is through the formation of soil aggregates. This occurs when tiny particles of soil clump together, sheltering carbon particles inside them. Mycorrhizal fungi, which produce sticky compounds that facilitate soil aggregation, are able to transfer 15 percent more carbon into the soil than other microbes. Soils with high clay content are also able to form chemical bonds that protect carbon from microbes. These aggregates give soil its structure, which is essential for healthy plant growth.

Some carbon, made up mainly of plant residue and the carbon exuded by plant roots, remains in soil only for a few days to a few years. Microbes can easily digest this “fast pool” of carbon, so it emits a great deal of carbon dioxide. The “slow pool,” where carbon can remain for years to decades, is composed of processed plant material, microbial residue from the fast pool and carbon molecules that are protected from microbes. A third “stable pool,” comprised of humus—decomposed organic material—and soil carbon that is well protected from microbes, is found below one meter deep and can retain carbon for centuries to millennia.

Interest Approach – Engagement (what will you do to engage students at the beginning of the lesson)

As students enter the classroom, have a question written on a large writing surface – What does the future of agriculture look like? Pick one or more of the videos below that give a glimpse into what the future of agriculture might look like.

KNOW: The Future of Farming https://youtu.be/Fr29UKzm2CI
The Future of Agriculture https://youtu.be/uAM4Si_WhDk
The Futuristic Farms That Will Feed the World https://youtu.be/KfB2sx9uCkI

Facilitate a brief student discussion about the future of food, the future of agriculture, and how to address some of the challenges.

Procedures

Present the content in the PowerPoint slide deck titled Future of Soils.pptx.
1. Goals of soil management
  1. Improve productivity
  2. Carbon sequestration
  3. Improve connected ecosystems – air and water quality
2. Improve productivity
  1. Healthy rhizosphere biology can lead to increased plant productivity
  2. Improved nutrient cycling
    1. Symbiotic relationships between plants, fungi, and bacteria
    2. Plants can obtain 80-90% of their nitrogen needs from mycorrhizal fungi partnerships
    3. Predator/prey relationships, for example between nematodes and bacteria, allow for nutrient availability
  3. Improved energy cycling
    1. Plants share carbon with their fungal and bacteria partners
    2. 30-40% of carbon created by photosynthesis can be exuded directly into soil via plant roots to nurture microbes
  4. Improved plant health and ability to fight disease and parasites
    1. Helpful bacteria can help ward off parasitic bacteria and other pests
  5. Increasing the carbon (organic matter) available in soil provides more food for the microbiome
  6. Better developed microbiomes lead to improved plant health
3. Sequester more carbon
  1. Atmospheric carbon dioxide levels have fluctuated throughout Earth’s history between 175 and 300 ppm
  2. Since humans have started burning fossil fuels CO ₂ levels have steadily increased to 383 ppm in 2007 and more than 400 ppm in 2013
  3. Some projections estimate levels will increase to 600 ppm by 2100
  4. Plants AND the microbiome play and important role in the carbon cycle and carbon sequestration
  5. The Earth’s soils contain about 2,500 gigatons of carbon—that’s more than three times the amount of carbon in the atmosphere and four times the amount stored in all living plants and animals.
  6. Currently, soils remove about 25 percent of the world’s fossil fuel emissions each year.
  7. Because almost half the land that can support plant life on Earth has been converted to croplands, pastures and rangelands, soils have lost 50 to 70% of the carbon they once held. This has contributed about a quarter of all the manmade global greenhouse gas emissions that are warming the planet.
  8. A 2017 study estimated that with better management, global croplands have the potential to store an additional 1.85 gigatons carbon each year—as much as the global transportation sector emits annually.
  9. Some scientists believe soils could continue to sequester carbon for 20 to 40 years before they become saturated.
  10. Basic Steps in C0 ₂, Soil/Carbon Cycle
    1. Photosynthesis: process where sunlight energy is transformed into biochemical energy – sugar called glucose. CO ₂ from the air and water from the soil. Releases O ₂ as a by-product.
    2. Resynthesis: glucose is resynthesized into a variety of carbon compounds including carbohydrates, proteins, organic acids, waxes and oil
    3. Exudation: 30-40% of carbon created by photosynthesis can be exuded directly into soil via plant roots to nurture microbes
    4. Respiration: carbon compounds created through resynthesis are used by plants, animals, or microbes to gain energy, grow, and maintain healthy systems. They respire carbon dioxide back into the atmosphere.
    5. Humification: creation of humus, a chemically stable type of organic matter composed of complex molecules (carbon, nitrogen, minerals, and soil particles). Carbon not used in microbial respiration can be converted to humus.
4. Improve connected ecosystems – air and water quality
  1. Healthy plants mean that fewer pesticides need to be used to treat problem species. Less chemical application means less impact on adjacent ecosystems.
  2. Improved microbiome – specifically for denitrifying bacteria – can lead to fewer nitrates leaching into the waterways. The bacteria return the nitrogen to the atmosphere in the stable N ₂ form.
  3. Improved microbiome can lead to quicker degradation of agrochemicals with less chance of leaching or run-off
  4. Improved microbiome can lead to more carbon capture and less atmospheric CO ₂
5. Best Management Practice - cropland
  1. No-till planting or conservation tillage planting
    1. Minimize disturbance of soil microbiome
    2. Increase organic matter left on fields
  2. Occasional tillage or conservation tillage
    1. Changes soil temperature and moisture that can be more hospitable to some microbes
    2. Can change the organic matter distribution in the soil making it available throughout the rhizosphere
  3. Fertility management
    1. Add animal manure to increase organic matter
    2. Apply soil amendments (fertilizer) based on soil tests and only apply where needed
  4. Buffer strips along edge of field, terraces, grassed waterways, and prairie strips in fields
    1. Slow water movement across fields
    2. Minimize soil erosion from fields
  5. Precision agriculture
    1. Minimizes machinery passes on the field which can then minimize soil compaction
    2. Apply pesticides and fertilizers at the right time to maximize efficacy and minimize negative impacts
  6. Perennial crops when possible
    1. Promotes continued symbiotic relationships
  7. Crop rotation
    1. Can influence quantity and quality of organic matter
    2. Affects hosting ability
      1. Breaks pathogen cycles
      2. Promotes symbiotic relationships with different species
  8. Cover crops
    1. Help reduce erosion during fallow months
    2. Promotes continual symbiotic relationship when cash crop is not actively growing
    3. Helps store nutrients like phosphorus that could be lost during erosion
    4. Helps build soil structure including macropore spaces
    5. Helps reduce soil compaction from heavy machinery
    6. Helps increase organic matter in soil
6. Best Management Practice - pasture
  1. Manage stocking rates closely
    1. Account for native grazers like deer and elk
    2. Account for excessively dry years with low forage production
  2. Manage access to water to minimize soil erosion
  3. Manage access to things like mineral/salt blocks to ensure animals move across the entire pasture
  4. Enhance riparian areas and manage natural water flow
7. Implement intensive rotational grazing
  1. Small pastures with short durations of grazing
  2. Mimics herds moving through the plains
  3. Gives plant communities a longer time to rest and recover
  4. Promotes perennials and reduces the spread of annual weeds
  5. Incorporates manure into the soil which increases organic matter
  6. Improves seed-to-soil contact for better germination

Facilitate student conversation throughout the presentation and check for comprehension. To apply this new-found knowledge and connect it with information from other lessons, students will participate in a Best Management Practice challenge. Divide the class into groups. Give half of the groups the worksheet for BMP cropland and the other half the worksheet for BMP pasture. Instruct them to follow the instructions and be prepared to present their ideas. Allow for 10 to 20 minutes of work time and then 30 minutes in which each group can make a 5-minute presentation.

Did You Know? (Ag facts)

The Earth’s soils contain about 2,500 gigatons of carbon—that’s more than three times the amount of carbon in the atmosphere and four times the amount stored in all living plants and animals.
Currently, soils remove about 25 percent of the world’s fossil fuel emissions each year.
Because almost half the land that can support plant life on Earth has been converted to croplands, pastures and rangelands, soils have actually lost 50 to 70 percent of the carbon they once held. This has contributed about a quarter of all the manmade global greenhouse gas emissions that are warming the planet.
A 2017 study estimated that with better management, global croplands have the potential to store an additional 1.85 gigatons carbon each year—as much as the global transportation sector emits annually.
Some scientists believe soils could continue to sequester carbon for 20 to 40 years before they become saturated.

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

Some agricultural companies are leading the way in new techniques that marry technology with improving soil biology. Have the students conduct research on one or more of these companies and write a synopsis of the company and their groundbreaking research. Potential companies for research are:
- Pivot Bio: https://www.pivotbio.com/
- Indigo Ag: https://www.indigoag.com/
- Mammoth Microbes: https://mammothmicrobes.com/

Suggested Companion Resources (books and websites)

Sources/Credits

This material is based upon work supported by the Natural Resources Conservation Service, U.S. Department of Agriculture, under number NR196114XXXXC003. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the U.S. Department of Agriculture. USDA is an equal opportunity provider and employer.
The grant by which this project is funded is administered by the Conservation Districts of Iowa.
ROOTS: Root and Soil Biology: Managing the “Microherd” for Max Tree Performance–Dr. Mark Mazzola https://youtu.be/Ok3cevqbTC4
Soil biology for crop and soil health. https://youtu.be/dlQjS67W3q0
https://blogs.ei.columbia.edu/2018/02/21/can-soil-help-combat-climate-change/

Author(s)