Water Quality - Nutrient Management and Cropping Systems - Lesson 11 Cover Crops

Water Quality - Nutrient Management and Cropping Systems - Lesson 11 Cover Crops

Target Grade Level / Age Range:

Grades 9-12

Time:

70 minutes

Purpose:

To understand the purpose and methods of using cover crops to maintain soil and water integrity.

Materials:

  • Dictionaries or computers/tablets with internet access
  • Writing utensils
  • Cover Crop Options sheet
  • Farmer Profiles Sheet
  • Farmer Profiles Key
  • Universal Soil Loss Equation sheet

Suggested Companion Resources (books and websites)

Vocabulary (with definitions)

  • Cover crops: a non-cash crop seeded at the end of the growing season that extends biological activity during the typical fallow season (late fall/early spring in Iowa)
  • Vernalization: the induction of a plant’s flowering process by exposure to prolonged cold of winter or an artificial equivalent
  • Monocotyledon: a plant with an embryo that bears a single cotyledon (leaf). Monocotyledons, also called “monocots”, typically have elongated, stalkless leaves with parallel veins (e.g., grasses)
  • Dicotyledon: a plant with an embryo that bears two cotyledons (leaves). Dicotyledons, also called “dicots”, typically have broad leaves with netlike veins (e.g., soybeans, dandelions, roses, etc.)
  • Nutrients: a substance that provides nourishment essential for growth and maintenance of life
  • Macronutrients: a substance required in relatively large amounts by living organisms. In plants, there are six macronutrients: nitrogen, phosphorus, potassium (the three largest), and calcium, magnesium, and sulfur.
  • Micronutrients: A substance required in trace amounts for the normal growth and development of living organisms. In plants, there are seven micronutrients: boron, molybdenum, chlorine, zinc, manganese, copper, and iron.
  • Forage: a plant used for food for livestock, including grasses and hay.
  • Herbicide: a chemical spray used to specifically terminate plants
  • Tillage: the preparation of land for growing crops; specifically cultivation
  • Legumes: a leguminous plant, or member of the pea family. Includes plants with a fruit that is contained in a pod, like beans, peanuts, and alfalfa.
  • Soil series: the lowest category of the national soil classification system, and described by the USDA – NRCS. Each series has names, like Clarinda, Tama, Gara, or Sparta, as well as map units, like 377C2 (meaning Dinsdale Soil Series, 5-9% slope, eroded).
  • Biomass: a mass of material of a living or once-living organism. In cover crops, largely means the amount of plant material the crop produces.
  • Organic material: plant or animal material or compost in the soil that helps build soil health and adds nutrients to the soil. Also called organic matter. (Organic here meaning carbon-based, not raised without chemicals.)

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

This lesson was created to be used in conjunction with the Water Quality – Nutrient Management and Cropping Systems curriculum. This lesson is the 8 th in the series. The previous lessons include the following topics: soil erosion, soil conservation, watershed decisions, nitrogen cycle, nitrogen runoff, soil structure, water cycle, solutions to run-off, and no-till farming. This lesson will discuss cover crops, what they are, how they are used, and how they impact the environment and finances of a farm operation.

In short, cover crops are crops that are planted during the “off-season.” These plants would be planted in the fall after the harvest of the main crop, and would remain in the field until the spring, when the main crop would need to be planted again. However, by using modified equipment and different seeding methods, some farmers establish their cover crops shortly before they harvest their main crop. That way, the cover crop is already working as ground cover by the time the main crop is taken off the field.

There are many kinds of plants that can be used as cover crops, and more research is being done to discover other good cover crops to use. In this lesson, there are two groups of cover crops that are covered. They are small grains and brassicas. Small grains (or cereal grains) include things like rye (the most common cover crop), triticale, and winter wheat. Brassicas are broadleaf crops that commonly have enlarged roots, like turnips or radishes. In general, small grains have root systems that help keep the soil in place better, but brassicas have larger taproots that can help alleviate compaction better and add more organic matter to the soil. Both of these groups establish well with aerial or broadcast seeding.

Cover crops can meet many objectives. The biggest objectives are soil conservation and water quality. These plants help keep soil in place during a time when it would otherwise be bare and vulnerable to wind and water erosion. Because they keep the soil in place, they also help keep nutrients in place, and help to stop fertilizers and other inputs from eroding into the water system.

In addition to these purposes, cover crops can also help suppress weed growth, increase soil tilth by adding organic matter and different root systems, help manage soil water content, and cover crops can serve as a feed crop for livestock in some operations.

There are many benefits of using cover crops, but logistically they can be difficult for some producers to implement. Cover crops are planted in the fall, after harvest of the main crop, and are terminated in the spring, before the planting of the main crop. These are already two of the busiest times of the year, and planning an extra step of planting or terminating a crop can be difficult. This is made more difficult when we often deal with wet springs in Iowa. Ideally, farmers want to be in the field about three days following a good rain. At this time, the soil is moist enough to be a good seedbed for the crops, but it is dry enough that the tractor will not cause excess compaction by driving through it.

Farmers also face difficulties with cost of cover crops. There is the cost of seed, cost of fuel to plant the seed, the value of time it takes, as well as the cost to terminate the plant in the spring, if herbicides, more fuel, and potentially new equipment are needed.

Because of the difficulties with timing, cost, and the needs of different crops, farmers have been very creative with ways to plant, terminate, and utilize their cover crops. Some farmers broadcast their cover crop seed using a broadcast seeder. Others will broadcast the seed, then incorporate it using tillage equipment. Others will use a planter they have modified for the smaller seeds. Others yet may hire an agricultural pilot to fly the seeds over the field with a small plane. Producers also have connected different machines together, so that they may harvest one crop while they plant the next, or in the spring, till under one crop while they plant the main crop. In the attached Cover Crop Options document, there are a few of the more common management options outlined. This document also outlines each of the five cover crops talked about in the lesson (rye, wheat, triticale, turnips, and radishes).

When students are introduced to the Cover Crop Options sheet, they may have more questions than the sheet answers. For instance, what kind of nutrients do the crops use? What are their root structures like? How soon will they emerge, etc. It could be easy for students to try to take too many factors into consideration and become overwhelmed. Encourage students to use knowledge they have of grasses, taproot crops, and soils, and make the best decisions they can with that knowledge. If students want to research crops more, many good resources are listed above in Suggested Companion Resources, and below in Sources/Credits.

This lesson starts with a general discussion about cover crops, their purposes, life cycles, and benefits. It then breaks down into three separate activities. The first activity assigns students to a specific scenario, in which they need to help make management decisions regarding cover crops. This activity is followed with an activity about calculating soil loss. Students will use information from their scenario to make calculations, and will then use those calculations to decide if any management decisions should be revised. Finally, students will be instructed to write a short paper summarizing their learning about cover crops.

Throughout this lesson, there are many careers that can be mentioned. Some include being a crop farmer, a soil conservationist, agronomist, seed scientist, agronomy researcher, agricultural engineer, chemical engineer, agricultural pilot, agricultural sales, agriculture business, animal nutritionist, watershed coordinator, or extension specialist.

Interest Approach or Motivator

Write a selection of the listed vocabulary words on the board. Assign each word to a different student and give students two minutes to research their word(s) and share it with the class. Students may use classroom books/resources or computers/tablets with internet access. Write the definitions on the board as they are shared.

Procedures

  1. Start class by asking students to summarize their knowledge of soil conservation so far.
    1. Students may talk about runoff and no-till farming, and the importance of keeping soil and nutrients in place.
  2. Ask students to describe ways that soil becomes eroded.
    1. Things like wind, rain, and overworking the soil can be mentioned. Floods and other natural disasters can negatively impact soils.
  3. Ask students to summarize what they know about plant life cycles and practices that can prevent erosion.
    1. Crops are planted in the spring and harvested in the fall, leaving fields empty from fall to spring. Some conservation practices include conservation tilling, no-till, contour farming, terracing, grassed waterways, buffer strips, and cover crops.
  4. Introduce students to the idea of cover crops by expanding on the time of year when there are no crops in the field. What happens during this time of year? Is there precipitation or wind? How would different tillage practices impact the soils during this time? Have students discuss and brainstorm what could happen to soils during this time and ways to curb the impact.
  5. Ask students if they have heard of cover crops. Ask them what benefits they think cover crops would have in soil conservation.
    1. Students can say things like roots holding soil in place, plant growth shielding soil from the elements, plant growth adding organic matter to soil, roots holding nutrients at the soil surface preventing leaching, suppresses weed growth, etc.
  6. Hand out information sheets about cover crops (Lesson 8 – Cover Crop Options), and walk through them as a class. Talk about reasons farmers may use cover crops, and factors they need to pay attention to. Walk through each cover crop and have short discussions about the pros and cons of each crop. Encourage students to take notes on their sheets during the discussions.
  7. Activity 1 – choosing a management system:
    1. For this activity, students will be assigned to a fictional farmer’s profile (Farmer Profiles document). Students can either work individually, or in groups of no more than five. Group students as desired, or distribute profiles to every individual student. Explain to students that they will need to read the profile and make decisions based on this information. The bottom half of the profile includes information that the students will need to fill in.
    2. For this activity, students will also need information about seeding and termination (in Cover Crop Options document).
    3. Give students about 15 minutes to make their decisions and record them in the correct places.
      1. Included is also a key to this document (Lesson 8 – Farmer Profiles Key.docx). It includes some reasonable choices for each profile. However, there can be many good answers for most of these questions. The important part is that students find key words to help them make good decisions, and use the short answer question to justify their reasoning.
    4. Once students finish working through their own scenarios, bring the class together as a large group to discuss their findings.
      1. Have at least one student from each farmer profile read the profile and walk through their decision-making process.
      2. Once someone from each scenario had been heard from, discuss as a group what different factors there were and how that impacted the decisions they made.
  8. Activity 2 – Universal Soil Loss Equation:
    1. This activity will expand on the first, in that they will use the background of their farmer and their decisions in the operation.
    2. Explain to students that there is an equation used to analyze the amount of soil lost on a field. It is called the Revised Universal Soil Loss Equation 2, or RUSLE2. This is put together by the USDA to help calculate soil loss. People like agronomists and conservation planners with the Natural Resource Conservation Service use this equation.
      1. The RUSLE2 equation is a very complex and requires a computer program and databases to use. While this is a great equation and very powerful, that does make it less accessible for beginners. For educational purposes, the worksheet uses a simplified and revised version of USLE (an older equation) for class use.
    3. Hand out the USLE worksheets to the students. Walk through the equation together as a class, pointing out where each value is pulled from. Take questions as they arise.
    4. Give students about 15 minutes to walk through the USLE equation using their operation decisions.
    5. If class time allows, discuss the findings. Which farmer was hardest to make decisions for? How did specific factors impact the USLE? What would happen to the equation if you changed tillage method? What would happen if slope changed?
    6. Ask students what things surprised them about making decisions regarding cover crops. Was it easy to calculate soil loss? What factors had they not before thought about?
  9. Activity 3 – summary essay:
    1. Before class is dismissed, assign students to write a one-page summary of cover crops. Tell students to include:
      1. Types of cover crops
      2. Growing seasons
      3. Uses and purposes of cover crops
      4. Factors farmers must consider regarding cover crops
    2. The NRCS’s Technical Notes are a good source for this paper. Three of these Notes are linked in the Suggested Companion Resources section.
    3. Tell students to turn the summary in in one week.

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

Did you know? (Ag facts)

  • Approximately 600,000 acres in Iowa were put into cover cropping systems in 2016. This represents a large increase from 10,000 acres from only a few years earlier. There are approximately 36 million acres in Iowa. That means that only 1.67% of acres are under cover crop.
  • Rye is the most common cover crop in Iowa.

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

  • Have students use the NRCS program, Web Soil Survey, to find their home and the soil series at their home. They can then research the series, and share the research with the class.

Sources/Credits

Author(s)

Chrissy Rhodes

Organization Affiliation

Iowa Agriculture Literacy Foundation

National Agriculture Literacy Outcomes

  • T2.9-12.b. Compare similarities and differences between organic and inorganic nutrients (i.e., fertilizer) on plant growth and development; determine how their application affects plant and animal life
  • 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

  • Science:
    • HS-LS1-5. Use a model to illustrate how photosynthesis transforms light energy into stored chemical energy. (cover crops)
    • HS-LS1-6. Construct and revise an explanation based on evidence for how carbon, hydrogen, and oxygen from sugar molecules may combine with other elements to form amino acids and/or other large carbon-based molecules. (cover crops)
    • HS-LS1-7. Use a model to illustrate that cellular respiration is a chemical process whereby the bonds of food molecules and oxygen molecules are broken and the bonds in new compounds are formed resulting in a net transfer of energy. (cover crops)
    • HS-LS2-4. Use mathematical representations to support claims for the cycling of matter and flow of energy among organisms in an ecosystem. (no-till, cover crops)
    • HS-LS2-5. Develop a model to illustrate the role of photosynthesis and cellular respiration in the cycling of carbon among the biosphere, atmosphere, hydrosphere, and geosphere. (cover crops)
    • HS-ESS3-1. Construct an explanation based on evidence for how the availability of natural resources, occurrence of natural hazards, and changes in climate have influenced human activity. (till v. no-till, cover cropping)
    • HS-ESS3-4. Evaluate or refine a technological solution that reduces impacts of human activities on natural systems. * (bioreactors, buffer strips, terraces, cover crops)
  • Math:
    • A-CED.A.3: Represent constraints by equations or inequalities, and by systems of equations and/or inequalities, and interpret solutions as viable or nonviable options in a modeling context.
  • Social Studies:
    • SS.9-12.G.1: Understand the use of geographic tools to locate and analyze information about people, places, and environments.
    • SS.9-12.G.4: Understand how physical and human processes shape the Earth’s surface and major ecosystems.
    • SS.9-12.G.5: Understand how human actions modify the environment and how the environment affects humans.

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