Know Your Boundaries

By Desiree Jans, Ph.D.

Certified organic crops are not guaranteed to be free of pesticide residues. Organic certification does, however, assure that producers follow specific standards to grow their crops. An important consideration is how to limit the risk of crop contamination by prohibited substances. The 2005 draft of the National Standard of Canada for Organic Production Systems specifies that an identifiable boundary area, called a buffer zone, must border an organic production unit.

Contaminants could be deposited on organic cropland by air or by water. Risk level depends on adjacent activities. Non-organic farming neighbours may use prohibited pesticides, soil amendments or seed sources. Air-borne pesticide sprays are notorious for drifting onto neighbouring fields. Contaminant-carrying soil can be moved by wind and water erosion. Contaminants can also come from activities on railways, roadways, power line right-of-ways, some watercourses and industrial buildings where prohibited products are used.

A less obvious source of contamination is from genetically engineered (GE) crops. Pollen from GE open-pollinated plants may cross-pollinate with non-GE plants. Pollen can travel long distances. For example, the Canadian Seed Growers Association attempts to protect certified seed crops from cross-pollination by setting minimum isolation distances: 800 m for hybrid canola and 200 m for corn. Some studies document that unpredictable wind currents and insect foraging can carry pollen over much greater distances. This is one reason that GE seed is showing up in supposedly non-GE seed stocks. Besides contaminated seed stock, GE seed can also end up in organic fields by falling from passing grain trucks or being carried by wind. Because all materials produced by genetic engineering are prohibited in organic agriculture, contamination by these materials may cost farmers their organic certification. Presently, the burden of avoiding GE contamination is borne by the organic producer. Sometimes this means limiting crop choices. A landmark legal battle continues in Saskatchewan as certified organic farmers seek compensation from Monsanto and Bayer Crop Science for losing canola as a crop choice due to risk of genetic contamination.

Well-designed buffer zones reduce the risk of contamination by trapping or diverting in-coming contaminants. The draft National Standard indicates that the buffer should be at least eight meters wide and, wherever feasible, contain a hedgerow or trap crop that is 1.5 times the height of the adjacent crop treated with prohibited materials. Specifics are case dependant, however. More extreme measures may be necessary adjacent to major sources of contaminants including GE crops. Chemical residue or genetic analyses may be required and if contamination is evident, the site must be taken out of certified organic production.

Treed hedgerows are often used in the buffer zone. Dense and tall plantings are effective windbreaks. In drier climates, hedgerows have the added advantage of trapping snow thereby improving spring moisture conditions. Wildlife also benefit from the diverse habitat that trees and shrubs provide. Consider, however, that land planted to trees will be out of agricultural production for some time. Tall trees may shade adjacent land and far-reaching roots compete with crops for nutrients. Maintenance will also be needed from time to time to keep the treed hedgerow in good condition.

The buffer zone can be planted to perennial grass or a grass legume mix. Although not as effective as a windbreak, a grass buffer does have advantages. Land can easily be converted back to arable use if the risk of contamination is eliminated (e.g. when you convince your neighbour that organic is the only way to go!). The grass buffer can also be harvested as livestock feed (although it would not be certified organic) or left as wildlife habitat.

Some producers grow crops in the buffer zone. This can be problematic because crops in the buffer zone are not eligible for organic status. Simultaneous production of organic and non-organic crops that are visually indistinguishable is called parallel production and is restricted by most certifying bodies. If similar crops are grown, producers must provide a system for visually distinguishing the organic and non-organic crops and must keep the two separate through production, storage and marketing. Meticulous record keeping is required.

Besides choosing appropriate vegetation, buffer zones should be designed with topography in mind. Consider prevailing wind direction to maximize trapping air-borne contaminants. Use swales, ditches, drainage and absorptive soils along water routes to divert water-borne contaminants.

In the end, the most effective buffer zone may be good neighbour relations. Organic producers are required to inform neighbours about their organic certification and problems that contamination with a prohibited substance would cause. Good neighbours will do their part to respect the boundaries.

Desiree Jans, Ph.D, is a Web Course Instructor for the Organic Agriculture Centre of Canada (OACC). For information about OACC courses or to send comments, contact us at 902-893-7256 or oacc@nsac.ca.

Posted on the OACC website, December 2005