Corn and the Environment - A Brief Overview

Corn is a major Ontario and Canadian grain crop which is unique because of its native Canadian origin and its high productivity. Because of its high productivity, its reliance on inputs to achieve this high productivity, and its association with many aspects of modern agriculture and related agri-food activity, concerns about the relationship between corn and environmental quality have been raised. The following is a brief overview of environmental aspects of modern corn production. More information is provided in other pages of this web site.

The process of photosynthesis is the basis for virtually all life. Some plant species are much more efficient than others in converting carbon dioxide and water into oxygen and organic matter. A highly efficient photosynthetic system, and a long period of seasonal growth, are why corn produces such high yields of organic matter (biomass) per hectare of land area per year, relative to most other plant species.
An average hectare of corn produces enough oxygen per hectare per day in mid summer to meet the respiratory needs of about 325 people. The one million or so hectares of corn grown in Ontario produce enough oxygen for the annual respiratory needs of Ontario's 10 million residents in about 11 summer days.
The rate of decomposition of dead corn plants is slower than for many other plants - this is one reason why corn stalks left on the surface provide good, long-term protection against wind and rainfall. The techniques of conservation tillage and "no-till" (also called zero tillage and no tillage), which are becoming popular on Canadian farms, mean slower rates of organic matter decay. Soil organic matter levels will increase as corn yield levels increase.
The fertility needs of corn tend to be higher, when expressed on per-hectare basis, than those of other crops. When fertilizer needs are expressed on a per-tonne-of-production basis, however, fertility needs for corn are similar to, or lower than, those of other grain crop species.
Although all corn varieties produce lower yields when insufficient fertility is available, higher yields are obtained with newer, rather than older, corn hybrids under conditions of low soil fertility. Newer hybrids use nitrogen more efficiently.
The quantity of pesticides used per hectare of land planted to corn is similar to that of major spring-seeded crops. Per tonne of crop yield, the rate of usage tends to be lower with corn. The quantity of pesticide usage per hectare and the real expenditure for pesticide purchases is trending downward for corn and other major field crops in Ontario. This trend to reduced rates is occurring despite a reduction in the amount of soil tillage. (Soil tillage is a "traditional," non-chemical method of weed control.)
Usage of atrazine has decreased by about two-thirds in Ontario, in part because of concerns over surface water quality, but mainly because this long-persistent herbicide is not well suited to the crop rotations which are now used by most farmers. A major survey of 1192 farm wells and ground water bores in corn-growing areas of Ontario found only two sites where pesticide concentrations exceeded Health Canada safe drinking water standards.
Newer hybrids are more tolerant of many stresses than were their predecessors, including the indigenous varieties grown centuries ago. These improvements include greater resistance or tolerance to weed competition, low fertility, shading and lodging.
Private corn breeding is supported by public research at locations such as the University of Guelph and several research stations of Agriculture and Agri-Food Canada. Major effort is being made, internationally, to preserve indigenous populations of corn for potential use in future breeding programs. An estimated 50,000 different types of corn exist in "genebanks" around the world.
Biotechnology offers the potential for further improvement in corn, including the opportunity to reduce pesticide usage through genetic improvements in insect and disease resistance.
Fossil-fuel energy is used to produce corn. However, analyses show that the energy output:input ratio with corn - i.e. amount of energy contained in harvested grain relative to the amount of fossil-fuel energy used for its production, including the production of inputs and equipment - is approximately 5.5:1 in Ontario. The energy ratio for corn compares favourably with that of other crops.
During a full growing season, an average hectare of corn in Ontario removes 22 tonnes of carbon dioxide from the air. The one million hectares of corn grown in Ontario will remove an annual quantity of carbon dioxide equivalent to that produced in burning about 9 billion litres of gasoline (about 75% of annual Ontario gasoline consumption).
Ethanol made from corn and other renewable, biological feedstocks is used extensively as an automotive fuel.

Ethanol represents a means of reducing net additions of atmospheric carbon dioxide emissions associated with transportation fuel usage. Ethanol represents an environmentally attractive substitute for lead, methylcyclopentadienyl manganese tricarbonyl (MMT), benzene and other undesirable compounds used as octane enhancers in gasoline. Ethanol represents a renewable, home-grown means of reducing dependence on imported crude oil.
Corn production in Canada includes features which could be classed as sustainable, and others which are not. Sustainable features include the use of sunshine, carbon dioxide and rainfall as the principal ingredients for corn growth. With conservation tillage techniques and higher corn yields, future soil organic matter levels can be expected to increase when land is planted to corn. Efficient use of livestock manure represents one means of reducing the need for synthetic nitrogen fertilizers. A second involves the use of high-nitrogen-fixing crops such as alfalfa in the crop rotation, although this can only occur if there is a use for the legume forage produced. Biotechnology may provide a solution if researchers are able to transfer nitrogen-fixing abilities, genetically, from legume species into corn [Top]