Cover Crops for Biomass Production

In mid-Iowa, cover crops with high fall biomass production are particularly valuable for improving soil health and water quality. Here’s an overview of the cover crops that typically produce the highest fall biomass in the region and the associated benefits:

Cover Crops with High Fall Biomass in Mid-Iowa

1. Oats (Avena sativa)
• Performance: Oats establish quickly and can produce high biomass if planted earlier in the fall. They do winterkill so they do not provide spring growth.
• Planting Time: Late summer to early fall for optimal biomass production. (8/8 – 9/25).

2. Cereal Rye (Secale cereale)
• Performance: Cereal rye is one of the most popular cover crops due to its ability to produce significant biomass in cool fall conditions. It germinates quickly and grows well even after late-season planting.
• Planting Time: Ideally after corn or soybean harvest (8/8 – 11/5).

3. Winter Wheat (Triticum aestivum)
• Performance: While slightly less vigorous than rye in fall, winter wheat still provides substantial biomass.
• Planting Time: Early to mid-fall (8/8 – 10/22).

3. Triticale
• Performance: A hybrid of wheat and rye, triticale combines the hardiness of rye with the quality forage potential of wheat, producing moderate to high fall biomass.
• Planting Time: Ideally after corn or soybean harvest (8/8 – 11/5).

5. Rapeseed (Brassica napus), Radishes (Raphanus sativus), and Turnips (Brassica rapa)
• Performance: These cover crops are fast-growing and produce good biomass in fall, especially in a warm early autumn. They winter kill for easy planting in the Spring.
• Planting Time: Early to mid-fall. 8/8 – 9/25.

6. Vetch, Hairy (Vicia villosa)
• Performance: relatively slow growing in the Fall. Adds substantial biomass in the Spring.
• Planting Time: Late summer to early fall for optimal biomass production. 8/8 -9/18.

7. Camelina (Camelina sativa)
• Performance: Freeze-hardy, early maturing brassica. Produces minimal biomass in the Fall. Grows quickly in the Spring
• Planting time: 8/8 – 11/5.

Benefits of Fall Biomass

1. Erosion Control
• Fall biomass provides a protective cover on the soil surface, reducing the impact of rain and wind. This helps prevent soil erosion, particularly on sloping fields.

2. Soil Structure Improvement
• High biomass from cover crops improves soil structure by increasing organic matter, enhancing soil aggregation, and reducing compaction.

3. Weed Suppression
• The dense cover from fall biomass suppresses weed germination and growth by outcompeting them for light, nutrients, and space.

4. Nutrient Scavenging
• Cover crops with high fall biomass uptake residual nitrogen and other nutrients, preventing their loss through leaching. This nutrient retention reduces potential water contamination.

5. Water Infiltration and Retention
• A robust root system improves soil porosity, enhancing water infiltration and retention, which helps manage field moisture levels.

6. Habitat for Soil Microorganisms
• High biomass provides food and habitat for beneficial soil organisms, contributing to a thriving soil ecosystem.

Considerations for Maximizing Cover Crop Biomass

• Planting Date: Earlier planting generally leads to more fall growth.
• Species Selection: Choose species based on specific goals (e.g., erosion control vs. nitrogen retention).
• Seeding Rate: Higher seeding rates may produce denser cover and more biomass.
• Fertility: Adequate soil fertility supports vigorous growth of cover crops.