GHGMP Feature Articles
Environment benefits from 50 percent less summerfallow
Continuous cropping taking over
A dramatic reduction in Canadian summerfallow acres over the last 10 years has produced a double benefit for the environment through reduced soil erosion, and a measurable reduction of greenhouse gas (GHG) emissions.
Statistics Canada shows the total summerfallow acres dropped from nearly 20 million acres in 1991 to about 10 million acres in 2002. And it appears the trend will continue.
The numbers reflect adoption by a growing number of producers of conservation farming practices that include zero tillage, direct seeding, chemfallow and continuous cropping. Although the change is driven by environmental concerns and the need to protect the soil, many producers have also found an important economic benefit from reduced machinery costs and in many cases improved production. The absence of tillage has also played an important role in reducing carbon dioxide emissions as more plant carbon is stored in the soil.
A Western practice
Summerfallow is largely a Western Canadian farming practice. It has been used through out the history of Prairie agriculture as a means of conserving soil moisture and weed control. Many farms, particularly in the driest areas, traditionally followed a 50/50 summerfallow rotation, which meant 50 percent of annual cropland was summerfallow each year.
Conventional summerfallow involves several light tillage treatments throughout the growing season to control weeds and conserve subsurface moisture. With the introduction of low-cost, broad-spectrum herbicides more producers have switched to a technique of chemical summerfallow, often referred to as chemfallow, which means crop residue is usually left on the soil surface during the fallow year and weeds are controlled with herbicides.
While farm census figures show a few thousand acres of land remained fallow in Eastern Canada, this is not being done to conserve moisture, says Dr. David Burton, Chair of Climate Change Research at Nova Scotia Agricultural College. "There may be land that's not seeded for rotational reasons or to control crop pests, but conventional summerfallow is largely non-existent," he says.
Major gains made
A concerted effort over the last 20 years has produced a dramatic reduction in conventional summerfallow acres in Western Canada. That move has been driven by a need to reduce wind and water erosion of soil, save time and at the same time, improve soil quality. Millions of tonnes of topsoil have been lost over the years from wind erosion alone. Tillage also contributed to a major decline in soil organic matter and overall soil quality.
"Conventional summerfallow contributed to a wide range of soil quality and production issues," says Peter Gamache, a long time Alberta soil conservation specialist and field co-ordinator of the Greenhouse Gas Mitigation Program (GHGMP) in Alberta. Along with the risk of soil erosion and loss of organic matter, summerfallow also contributed to soil moisture loss, in some cases an increase in soil salinity, loss of soil tilth and texture and a reduction in soil micro-organisms.
"Producers began to see declining productivity of their land," says Gamache. "And while it's an issue that's only been recognized in recent years, the practice also increased the release of carbon dioxide into the atmosphere."
Contributes to carbon dioxide levels
Soil organic matter stores the atmospheric carbon, which is collected by plants during the growing season. With the loss of organic matter, the carbon is released back into the atmosphere as carbon dioxide. Through chemical conversion one tonne of carbon actually produces about 3.6 tonnes of carbon dioxide.
Education and awareness programs have been geared to show producers that conservation farming practices such as zero and reduced tillage and direct seeding, can conserve soil moisture and actually increase crop yields even under continuous cropping. Reduced herbicide costs, too, make chemfallow an economic option.
"Farmers have really adopted the new production technology," says Blair McClinton, another long-time soil conservation specialist and field co-ordinator of the GHGMP in Saskatchewan. "For many, summerfallow was just a traditional practice they felt they had to do to produce a crop."
Practice eliminated or modified
The amount of summerfallow acres has declined in Western Canada by as much as 50 percent over the past decade. Alberta and Saskatchewan have seen the biggest change. Manitoba was not a big summerfallow province due mainly to a higher moisture growing regime, which in some areas required producers to develop strategies to deal with too much moisture, rather than moisture conservation.
In the past decade, summerfallow acres in some of the western regions of Manitoba have declined from about 800,000 acres to about 630,000 acres. About half of the summerfallow is conventionally tilled, while the other half is a combination of chemfallow and tillage.
Saskatchewan has seen the largest reduction in summerfallow - from about 17 million acres of conventional summerfallow in 1971 to about seven million acres or about 20 percent of cultivated acres in 2002 are in summerfallow. "We expect that trend to continue," says McClinton.
Also a growing percentage of total summerfallow, about 1.5 million acres is straight chemfallow, while another 1.5 million is a combination of chemfallow and tillage.
In Alberta, summerfallow acres have declined from nearly four million acres in 1994 to about 2.5 million acres today, says Gamache. While 60 percent of the total acres were tilled a decade ago, that dropped to about 39 percent by 2002, with 24 percent of straight chemfallow and about 37 percent as a combination of chemfallow and tillage.
"The message is being heard," says Doug McKell, executive director of the Soil Conservation Council of Canada. The council is administering the soils component of the federally funded Greenhouse Gas Mitigation Program. "We've made great strides in the last 10 to 15 years, but more work needs to be done through education, research and demonstration to introduce producers to these improved and sustainable farming practices."