Duration: 50 minutes
Objective: To understand the importance of cover cropping in sustainable agriculture.
Organic agriculture is heavily dependent on cover cropping- the implementation of plants to improve an agroecosystem. A cover crop can add organic matter, add nutrients, fix nitrogen, suppress weeds, control erosion, manage insect pests and attract beneficial insects.
- cover crop seed
Begin the lesson (25 minutes):
1. Gather students.
Say: When we are not growing vegetable crops, we plant things in the soil to improve the health of the garden. These are called cover crops. Cover crops can have many purposes. In our winter, a major advantage of planting a cover crop is erosion control.
What is erosion?
What are the biggest forces of erosion in our garden? (wind, rain)
What other uses of a cover crop can you think of?
Include in your discussion that cover crops are any crop grown to provide soil cover for the purpose of soil sustainability and improvement, NOT for human food consumption, regardless of whether it is later incorporated into the soil. They are often considered “green manure.”
2. Provide some examples of cover crops explaining that some are annuals (buckwheat, barley, oat, spelt, annual rye, wheat), some biennials (winter rye) and some perennials (perennial rye, red clover, yellow blossom clover, white clover, hairy vetch).
3. Ask: What are the benefits of cover crops?
Include in your discussion that:
• Nitrogen production from leguminous cover crops (alfalfa, clovers, and vetch) improves conditions of poor soil by increasing soil fertility.
• The addition of organic matter to the soil. as the cover crops and green manuresdecompose improves soil structure and increases soil drainage.
• Nutrient enhancement (nitrogen, phosphorus, potassium, sulfur, calcium, etc). As the cover crops and green manuresdecompose in the soil, they add nutrients tothe soil which will benefit the next crop
• Weed prevention/suppression. All cover crops compete with weeds for sunlight, moisture and nutrients, thus slowing down the weeds’ growth, sometimes even smothering them out completely. Certain cover crops such as buckwheat, barley, oat, winter rye exhibit “allelopathy” — the ability to produce certain chemical toxins which inhibits weed seed germination and growth. Even the mulch from these crops after mowing them down can significantly reduce weed growth.
• Rooting action. The extensive root system of certain cover crops, for example, winter rye, can effectively break up compacted soil and significantly increase soil permeability and aeration.
• Soil erosion control. Roots of cover crops reduce soil erosion during periods of high wind and heavy rain by holding on to the soil and absorbing the rainwater. Above ground plant parts also help to reduce soil erosion by deflecting the wind and raindrops, thus minimizing soil crusting, reducing soil loss and surface water run-off during such conditions.
• Pest management. Many cover crops provide nectar and pollen which attract beneficial insects, add diversity to the system and keep the pest populations in check once the main crop becomes established.
• Incorporation into crop rotation. Cover crops can be planted during the “off” season when the field or gardening bed is fallow. For example, a farmer that uses a corn/ soybean rotation system can plant corn in spring and summer (and harvest), then plant winter rye for fall and winter, till/incorporate the rye into the soil the following spring, then plant soybeans.
• It’s good practice for farmers and home gardeners alike. Farmers in developing countries who might not have the resources to buy expensive synthetic (chemical) fertilizers are increasingly turning to cover crops as ways to improve soil fertility (also taking advantage of all other benefits cover crops can offer). Some farmers in the U.S. are also becoming increasingly aware of soil sustainability issues and incorporating cover cropping techniques into their farming.
4. Choose a few cover crops to plant in the fall. See if this reduces the amount of soil loss due to winter storms, if it increases the soil’s permeability and aeration and if it decreases the
amount of compost that needs to be added to the plots during the growing season.
What are OUR main contributors to erosion in this garden?
- Studying birds as garden pests: Experiment with spreading consistent amount of seeds on the beds. Leave some uncovered, and some covered with Remay. Compare the germination to understand the damage birds can do to the cover crop seed!