Cover Crops

Cover Crops

Frequently Asked Questions

  • Although we do not offer wheat in our mixes, there are various benefits for using wheat as cover crops. However, there are a couple of risks you should consider:
  • Wheat and Barley do not fix atmospheric nitrogen.
  • Wheat and Barley may compete for nitrogen resources with the next crop.
  • Wheat and Barley may not be killed over winter (and might require active termination) and can become a weed if not managed well.
  • Wheat and Barley may host diseases that affect subsequent crops (ensure crop rotation).
  • Depending on seeding rate, your costs might be higher than other cover crops.

There are various benefits for using rapeseed (canola) as cover crops, it is very affordable and can break up compacted soil layers. However, residue in the soil might compete for nitrogen with your next crop. Also, there is a high-risk of volunteer plants in the subsequent crops as rapeseed requires careful management to avoid becoming invasive:

  • High Adaptability: Rapeseed can adapt to a wide range of environmental conditions, allowing it to thrive in various climates and soil types.
  • Aggressive Growth: It has a vigorous growth habit and can quickly establish itself, outcompeting native vegetation for resources such as light, space, nutrients, and water.
  • Prolific Seed Production: Rapeseed plants produce a large number of seeds that can spread over considerable distances by wind, water, animals, and human activity.
  • Seed Dormancy: The seeds of rapeseed can remain dormant in the soil for several years, which means that once established, the plant can be difficult to eradicate and can re-emerge after initial control efforts.
  • Lack of Natural Predators: In areas outside its native range, there may be a lack of natural predators or control mechanisms to keep its population in check.

Radishes, particularly varieties known as “tillage radishes” or “daikon radishes,” are used as cover crops but their nitrogen benefits function differently compared to leguminous cover crops. Radishes do not fix atmospheric nitrogen. However, they can contribute to nitrogen management and soil health in several ways:

  • Nitrogen scavenging: Radishes have deep, robust taproots that can reach into the soil and absorb nitrogen and other nutrients that are beyond the reach of shallower-rooted plants. This ability to scavenge nutrients from deep in the soil profile helps prevent nitrogen leaching into groundwater, effectively capturing and recycling nitrogen within the soil.
  • Bio-drilling: The deep taproots of radishes can break through compacted soil layers, improving soil structure and aeration. This process, often referred to as “bio-drilling,” helps increase infiltration and can bring subsoil nutrients, including nitrogen, closer to the surface where subsequent crops can access them more easily.
  • Residue decomposition: After radishes die, usually due to winter frost, their roots decompose quickly, creating channels in the soil that improve water infiltration and root penetration for following crops. The rapid decomposition of radish tissue also releases stored nutrients, including nitrogen, back into the soil, making them available for the next crop.
  • Weed suppression: The rapid growth of radish cover crops can suppress weeds, reducing competition for nitrogen and other nutrients.

Cover crops can be highly beneficial for bees, offering them a source of forage, especially during times when other flowers may not be abundant. From the list you provided, the following cover crops are particularly beneficial for bees:

  • White Mustard: flowers of white mustard can provide pollen and nectar for bees. They are attractive to a variety of pollinators, including honeybees.
  • Brown Mustard: mustards are generally good for bees, and brown mustard is no exception, providing a good source of pollen.
  • Oil Radish: like mustard, the flowers of oil radish can offer food resources for bees.
  • Asian Radish: this is another variety of radish that blooms and can support bee populations.
  • Early Hairy Vetch: hairy vetch has been noted for its attractiveness to bees. It not only provides nectar but also can host bee larvae as a pollen source.
  • Purple Vetch: like hairy vetch, purple vetch is beneficial to bees for its nectar and as a pollen source.
  • Berseem Clover: clovers are excellent for bees, and berseem clover flowers are a particularly good source of nectar.

These crops flower at different times, providing bees with a succession of foraging opportunities. Additionally, the diversity of plant species can support a wide range of bee species, including both wild bees and managed honeybees. Cover crops that flower provide the added ecological benefit of supporting pollinator populations, which are crucial for the pollination of many crops and the overall health of ecosystems.

Biomass in the context of cover crops refers to the total mass of living plant material, including leaves, stems, and roots, which cover crops produce. The role of biomass in cover crops is multifaceted and crucial for various ecological and agronomic functions.

Role of biomass in cover crops:

  • Soil Protection: A significant biomass above the ground provides a protective layer over the soil, shielding it from the impact of raindrops, reducing erosion, and helping to conserve moisture.
  • Weed Suppression: Thick biomass can suppress weeds by outcompeting them for light and space, reducing the reliance on herbicides.
  • Nutrient Cycling: As the biomass decomposes, it releases nutrients that were absorbed from the soil back into the soil, enhancing its fertility.
  • Soil Organic Matter: The addition of biomass to the soil increases organic matter content, which is critical for improving soil structure, water-holding capacity, and the soil’s ability to provide nutrients to plants.
  • Microbial Habitat: Biomass provides habitat and food for soil microorganisms, which are essential for nutrient cycling and soil health.
  • Carbon Sequestration: Biomass from cover crops captures atmospheric carbon dioxide through photosynthesis, storing carbon in the soil when it decomposes, which helps mitigate climate change.


  • Better Soil Protection: More biomass means more ground cover, leading to better protection against erosion and moisture evaporation.
  • Greater Weed Suppression: A denser biomass can more effectively suppress weed growth.
  • Enhanced Soil Health: More organic material incorporated into the soil can improve soil structure and fertility.
  • Higher Nutrient Recycling: The more biomass there is, the more nutrients can potentially be recycled back into the soil.
  • Climate Change Mitigation: More biomass can lead to greater carbon sequestration.


  • Difficulty in Management: Large amounts of biomass can be challenging to manage, particularly when it comes to terminating the cover crop and preparing for the next crop.
  • Slower Soil Warming: Thick biomass can insulate the soil, which may delay soil warming in the spring.
  • Increased Pest Habitat: Sometimes, high biomass can provide habitat not only for beneficial organisms but also for pests.
  • Nitrogen Immobilization: If the biomass has a high carbon to nitrogen ratio, it can temporarily immobilize nitrogen in the soil as microorganisms break down the carbon-rich residues.

Cover crops contribute to soil biodiversity by providing a continuous habitat for microorganisms. This promotes a symbiotic relationship where microbes facilitate nutrient cycling and disease suppression, enhancing rhizosphere dynamics and soil resilience.

Certain cover crops can release allelochemicals—bioactive compounds that suppress the germination and growth of competing plant species, effectively reducing weed pressure and influencing succession in crop rotations.

By taking up excess nutrients, especially nitrates, from the soil profile, cover crops minimize the risk of these nutrients leaching into groundwater (making them available for subsequent crops).

Cover crops can reduce greenhouse gas emissions by enhancing carbon sequestration in the soil, improving nitrogen use efficiency, and reducing the need for synthetic fertilizer applications.

Cover crops can influence soil pH by adding organic acids and plant residues to the soil, potentially lowering pH in alkaline soils or, through decay and nutrient cycling, raising pH in acidic soils.

Cover crops can act as a barrier or trap crop, interrupting the life cycles of certain pests and diseases, thereby reducing the incidence of these problems in subsequent crops.

A high C:N ratio can temporarily immobilize soil nitrogen as microbes decompose residue, while a low C:N ratio can lead to quicker decomposition and nitrogen release. This must be managed to synchronize with the nitrogen demands of subsequent crops.

Cover crops enhance soil physical properties by increasing soil organic matter content, improving soil texture and bulk density, and contributing to soil structure formation and stability.

Mix design should be based on desired ecosystem services such as nutrient cycling, soil structure enhancement, and biodiversity. It requires understanding synergistic effects among species to optimize service delivery.

In arid climates, cover crops with deep rooting systems can access deeper moisture and bring it to the surface for subsequent crops. Species selection and management are key to ensure they do not deplete soil moisture excessively.

Mechanical termination methods like mowing or rolling/crimping can add to soil organic matter and protect soil structure, while herbicide use may have non-target effects on soil biota and require careful consideration.

The biomass produced by cover crops can dilute herbicide concentrations, potentially affecting their efficacy. Additionally, the microbial activity stimulated by cover crops can alter the rate of herbicide breakdown.

Certain cover crops, particularly brassicas, can be used as biofumigants due to their glucosinolate content, which, when broken down, releases compounds that can suppress soil-borne pests and pathogens.

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