What are sustainable agroecosystems?

What determines the colour of an egg yolk?


sustainable agricultural ecosystems

A farm can be considered an ecosystem – it consists of living and non-living things that interact and exchange energy. A farm ecosystem, however, is different from natural ecosystems because humans control many of the interactions.

Natural resources that are essential in a farm ecosystem include soil, water, plant and animal diversity, vegetation cover, renewable energy sources and climate. A sustainable agriculture approach uses these natural resources so that their renewable capacity is not reduced. A sustainable approach also ensures that natural ecosystems are not harmed.

A growing approach to sustainable farming involves the design of farming systems that recognize the important functions of natural ecosystems. These approaches are referred to as agroecosystems. They rely on natural nutrient and energy cycles.

What are the living and non-living things that are part of farm ecosystems? What interactions can you identify?



feeding livestock

About 30 percent of global arable land is used to produce animal feed. The production of feed, as well as the use of manure for fertilizer, are both part of nutrient cycling in agroecosystems. 

In Canada, the makeup of livestock feed varies from province to province, and even from region to region, depending on what is most available or climate conditions over time. Challenging growing conditions can affect where feed for livestock is obtained, which can also affect cost and quality.

The feed industry is an important part of Canada’s agri-food economy and an essential partner in the country’s food safety system. Feed represents the largest input cost for livestock and poultry producers — up to 75 percent of the total cost of production, depending on the species. About 90 percent of all animal feed in Canada is manufactured by feed mills that produce about 20 million tonnes per year for Canada’s farmers.

Feed mills follow strict guidelines that govern the ingredients that can be used. These guidelines are administered by the Canadian Food Inspection Agency (CFIA). However, some farmers will mix their own feed to obtain the right proportion of ingredients for their animals. They follow guidelines set by animal nutritionists. 

The grains most widely used in feed production are corn, wheat and barley, with soybean and canola providing major protein sources. Alfalfa hay is a good quality feed component that provides protein to dairy cattle.

The main ingredient of all chicken feed — over 85 percent — is grains and grain by-products, protein-producing seeds, and meal made from these seeds. Therefore, essentially all chicken is “grain-fed.”

In much smaller quantities — around 10 percent — various other protein sources such as meat and vegetable fats are added to improve the nutritional content, taste and texture of the feed.

Some birds are raised without any animal byproducts, but since chickens are omnivores, these need to be replaced with vegetable sources so that bird health is maintained. In much, much smaller quantities – around 1.5 percent – mineral and vitamin supplements can be added to prevent any nutrient deficiencies.

How is crop and livestock agriculture interrelated? How do you think this affects the agroecosystem as a whole?



Consider the following news article from Agriculture and Agri-Food Canada. How does this research relate to nutrient cycling in an agroecosystem? How does it support sustainable agriculture?



Beef and dairy farmers around the world are looking for ways to reduce methane emissions from their herds to reduce greenhouse gas emissions – a global priority. To help meet this goal, researchers from Canada and Australia teamed-up for a comprehensive three-year study to find the best feeding practices that reduce methane emissions while still supporting profitable dairy and beef cattle production.

“We need to know how feed affects methane production, but we also need to know how it affects other aspects of the farm operation, like daily gains in animals, milk production, and feed efficiency.” Researchers looked at three supplements.

Methane Inhibitor 3NOP is a promising commercial feed supplement that can be given to cattle to inhibit the enzyme methyl coenzyme M reductase – an enzyme responsible for creating methane in the animal’s rumen (first stomach). After blocking the enzyme, 3NOP quickly breaks down in the animal’s rumen to simple compounds that are already present in nature.







Story of Nitrate Researchers in Canada found that adding nitrate to the diet of beef cattle reduces methane production by 20 percent in the short-term (up to 3 weeks), and after 16 weeks it still reduced methane up to 12 percent. In addition, feeding nitrate improved the gain-to-feed ratio.

Microorganisms in the cattle’s rumen need nitrogen to be able to efficiently break down food for the animal to absorb. Nitrate is a form of non-protein nitrogen similar to that found in urea, a compound used in cattle diets. When nitrate is fed to cattle, it is converted to ammonia which is then used by the micro-organisms. During this process, nitrogen in the nitrate works like a powerful magnet that is able to hold onto and attract hydrogen. This leaves less hydrogen available in the rumen to attach to carbon to make methane, thus reducing the amount of methane produced. 

Wheat, corn or barley? In the short term, wheat effectively reduced methane production by 35 percent compared with corn or barley grain; but, over time cattle were able to adapt to the change in feed and the methane inhibitory effect disappeared. Essentially, after 10 weeks, methane production was the same for corn, barley and wheat.

Read the full article HERE.

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