A New Twist on Cropping - Living Legume Mulches (2008)

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Many producers are interested in sustainable crop production systems that reduce the application of chemical fertilizers and pesticides. Incorporating a 'living mulch' in cereal silage production might help achieve this for certain producers.

Living mulches are a form of intercropping. Intercropping is the cultivation of two or more plant species in the same field at the same time. A living mulch is an established legume cover crop into which an annual row crop is seeded. Often that annual row crop is a cereal, such as triticale or barley. Forage legumes are ideal for use as living mulches because they can be low growing and perennial. Using a perennial forage legume allows the living mulch to be maintained for multiple years without reseeding.

There are many benefits to using a legume living mulch. Forage legumes fix nitrogen through their relationship with soil microbes called rhizobia. If more nitrogen is fixed than the legume plant needs, this excess nitrogen may be released into the soil. Once in the soil, the nitrogen can then be taken up by the cereal crop. Decomposition of legume leaves and roots also adds nitrogen to the soil.

The ground cover provided by the legume living mulch helps control weeds through competition. For example, the legume living mulch can shade emerging weed seedlings, reducing their growth. The legume living mulch can also decrease cereal leaf disease incidence by acting as a barrier to pathogen spread between cereal plants.

The legume and cereal occupy different above and below-ground niches. They complement each other, increasing the cropping system's ability to capture and use resources, such as sunlight, water, and soil nutrients, efficiently.

The legume living mulch can increase the economic sustainability of a producer by decreasing the need for expensive inputs, such as nitrogen fertilizer and herbicides. It can also increase his environmental sustainability by providing constant ground cover to reduce wind and water erosion

Growing a cereal for silage in a forage legume living mulch would increase its forage quality. The protein-rich legume leaves would increase the crude protein content of the silage, while decreasing fibre levels.

Some suppression of the established living mulch in the spring before seeding your cereal is needed. This suppression could be a reduced herbicide application ten to 14 days before seeding or mowing the legume a couple days before.

What forage legume would be a good candidate for use as a living mulch? A fairly fast establishing, low growing legume would be ideal. If you are planning on maintaining the living mulch for multiple years, longevity and winter-hardiness would be two other characteristics to consider. Ultimately, the legume you choose will depend on the growing conditions in your area, and could vary from alsike to white to red clover for example.

One legume that has shown promise as a living mulch in Alberta is kura clover. Kura clover is relatively new to the province, and is currently used in the United States in mixed pastures. Kura clover living mulches have the potential to be adopted for barley or triticale silage production in Alberta, creating systems with lower input costs and increased forage quality.

For more information please contact
Stephanie Kosinski, Forage Specialist with Alberta Agriculture
Email: Stephanie.Kosinski@gov.ab.ca

Source: The Blade - Grey Wooded Forage Association, May 2008.

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