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Pasture management
Cattle are the primary source of methane emissions in Canadian agriculture. In Manitoba, enteric fermentation, or methane emissions, from ruminant livestock (primarily cattle) produced about 45 percent of the agricultural emissions in 2004.
Methane is produced in the rumen as microbial fermentation takes place. Up to 12 percent of the energy in the feed may be emitted as methane. (1) In addition to the production of greenhouse gases, this loss of feed energy as methane also represents lost profit for producers, since a significant portion of the feed consumed is not being converted to animal protein.
The best way to reduce methane emissions is by improving feed efficiency. And using high quality forage is one of the most effective ways to do this.
Research in Manitoba, for instance, showed that methane emissions from grazing steers on high quality pastures were 50 percent lower than emissions from those grazing on poor quality pastures. (2)
Rate of consumption by cattle is improved with abundant high quality forage, thus reducing time spent grazing and making the digestion process more efficient.
Grazing time could drop from 10–13 hours per day to five hours per day, meaning significantly lower methane emissions. The faster the digestion, the less methane that is produced per unit of feed consumed. (3)
Healthy forage stands can also increase carbon stored in the soil, prevent soil erosion and protect water quality. (4)
Here are some key ways to ensure high quality forage, while also protecting the land.
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Rotational grazing
Rotational grazing—alternating periods of grazing and time for plant recovery—helps ensure even pasture growth, resulting in less weed encroachment and a healthier forage stand. (5)
If a pasture is grazed unevenly, cattle end up expending a lot of energy trying to get what they like to eat from the regrowth. Uneven growth can lead to lower pasture productivity and more energy expended by cattle when grazing. (6)
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Intensive grazing
Intensive grazing on grass-legume pastures is another way to increase pasture productivity. This practice of using rotational grazing with multiple small paddocks and careful, often daily, management can increase profits while also benefiting the soil. Most practitioners can increase the pasture’s carrying capacity by 30 to 60 percent in the first five years. However, intensive grazing requires more time and knowledge for it to work effectively. (7)
Intensive grazing, however, can result in more nitrous oxide emissions from the increased amounts of manure and urine left behind. So intensive grazing on a pasture should be followed by a significant rest period for the plants to recover adequately. This will allow the pasture to utilize any excess soil nitrogen that could be lost as ammonia or nitrous oxide. (8)
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Overgrazing
Overgrazing occurs when a plant that has been grazed is grazed again before it has regrown and replenished its root reserves. If regrazing continues, the plant may eventually die. Short grazing periods will ensure regrazing does not occur. (9)
Putting cattle out to pasture too early in spring and leaving them out too late in fall is another way that overgrazing happens. This can degrade pasture quality bit by bit every year. (10)
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Legumes
Adding some legume forages such as alfalfa or clover to the pasture mix will ensure there is adequate nitrogen in the diet to aid digestion of plant fibres, resulting in less methane production. (11)
Legume forages also provide pasture grasses with adequate nitrogen, and reduce the need for inorganic nitrogen fertilizer, which in turn reduces the greenhouse gas emissions associated with its production. (12)
Even having as little as 25 percent legume in forages can result in significantly higher feed efficiency, leading to substantial decreases in methane. (13)
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Perennial_forages
Forages provide a sink for carbon in the plant itself, while also increasing the organic matter content in the soil. Perennial forages reduce the frequency of soil tillage, prevent soil erosion and help protect water quality. (14)
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Pasture fertilization
Fertilization with inorganic fertilizer, manure or compost encourages more vegetative growth and improves pasture productivity. This will also encourage more carbon sequestration in the soil. (15)
However, the use of inorganic fertilizers on pastures needs to be considered on the basis of economic benefit, potential environmental impacts and the energy requirements of inorganic fertilizer production, which uses significant quantities of fossil fuels.
