Can Organic, Conventional and Genetically Engineered Cropping Systems Coexist?


The coexistence of differing varieties and production methods is not new to agriculture. Breeders and farmers have developed strategies to grow and market different varieties, such as white and yellow maize, hot and sweet peppers, high- and zero-erucic acid rapeseed, and still achieve purity standards dictated by certified seed specifications. When producing crops in or for countries where labeling thresholds exist for AP of GE products (see “What Happens When Pollen Moves From Genetically Engineered Crops to Wild Relatives or Non-Genetically Engineered Varieties? In Areas of Genetic Diversity “), methods must be established to separate different product lines to enable coexistence so the economic needs of all farmers can be met (1) (see “What Happens When Pollen Moves From Genetically Engineered Crops to Wild Relatives or Non-Genetically Engineered Varieties? In Areas of Genetic Diversity").

Farmers also have to choose among various production methods to grow their crops; it is not uncommon for different farming systems to be used on adjoining fields. Thus, farmers have to deal with mixing of permissible inputs and methods, whether within their own farms, with products from neighboring farms, or during harvest and processing. This commingling or AP is the unintended occurrence of materials other than the specific crop and can include weed seeds, seeds from other crops, dirt, insects, and other foreign material, such as stones or plastic. For seed crops, rules for AP are specified by the Association of Official Seed Certifying Agencies (AOSCA). For example, a level of 0.5% seed of other varieties and 2% AP of inert material is permitted in “pure seed” of hybrid corn seed (2).

Historically, dealing with practices of neighboring farms has been handled by farmers working with each other to minimize impacts. This situation occurs, for example, when synthetic pesticides are used on conventional farms and organic farming is being practiced on adjoining fields. This situation can cause economic losses for the organic farmer when prohibited pesticide residues (3) occur at levels >5%of the EPA’s tolerances, because the product cannot be sold, labeled, or represented as organically produced (4). Thus, coexistence strategies must be devised to allow both neighbors to farm in an economically viable manner. This can involve alerting each other to their plans and modifying them to accommodate each others’ needs. When GE crops are grown next to organic farming operations, certain practices that minimize synthetic pesticide drift can also limit GE gene flow, such as spatial separation of fields, staggered planting dates, and planting varieties with different maturity dates and those that are not sexually compatible. Other crop-specific methods have been devised to aid coexistence strategies (5, 6, 7). Gene flow is not the only means for GE to commingle with conventional or organic crops; crops must also be segregated during harvest, shipping, and processing. Methods limiting such commingling have in some cases been implemented (5, 8, 6, 9, 7).

The European Commission on Agriculture and Rural Development adopted guidelines in 2003 for the development of national strategies and best practices in the European Union to ensure coexistence of GE crops with conventional and organic farming (10). Individual European Union countries have developed their own coexistence strategies (11), which has led to differences in the legal and economic situations within the European Union (12). Country-tocountry growing conditions are so varied and experience with GE crops is still so limited that it is difficult at present to develop unified legislation on coexistence. The European Commission is set to release a report describing the development of national coexistence measures (14).

In 2006 the UK DEFRA outlined a protocol on how to manage coexistence, with stricter standards for coexistence with organic products (15). The aim was to ensure future growing of GE crops without resultant disadvantages to any farmer. The legislation establishes statutory separation distances between compatible GE and non-GE crops, which are specific for each crop and which account for the size of receptor and donor fields, and a statutory notification process to inform neighboring farms. Nonstatutory recommendations include control of volunteers and bolters (sugar beet) and cleaning of shared combine harvesters. Feedback was sought from stakeholders (14) with the intent that by the time GE crops are released in the United Kingdom appropriate coexistence measures will be in place. To facilitate spread of information and compliance, a web-based Coexistence Information System was created to share information on studies being conducted in individual European Union countries on specific GE crops (16).

One factor hampering coexistence is the demand for zero tolerance for GE presence. Achieving 100% purity with any biological system is impossible and would require a complete ban on growing GE crops. In the United States AOSCA sets “minimum standards for genetic purity and identity and recommended minimumstandards for seed quality for the different classes of certified seed” (17), and this is made possible through coordinated efforts of official seed certification agencies that evaluate, document, and verify that a seed or plant product meets accepted standards (18). Mandatory practices are established by state affiliates of AOSCA that set isolation distances from fields of the same crop, use of buffer rows, and specified agronomic practices, such as rouging of undesirable plants, weed control, and detasseling (19). This type of approach could also assure reasonable purity standards for commingling ofGEin agricultural products. WhenUK officials drafted DEFRA guidelines, they recognized that rules need to be achievable because the more complex the system, the more likely farmers would be to err or ignore the rules (20). Also critical is establishment of accurate methods to test for GE presence, availability of a testing facility, an economical cost for testing, established liability criteria, and compensation schemes once GE presence is detected (21).


1. Int. Seed Fed. 2004. Coexistence of genetically modified conventional and organic crop production, pp. 1-3. Last accessed 2011-12-5. PDF

2. Kershen DL, McHughen A. 2005. Adventitious presence: Inadvertent commingling and coexistence among farming methods. CAST Comment. QTA2005-1, July

3. Natl. Org. Program (NOP). 2008. National list of allowed and prohibited substances. Last accessed 2011-12-5. PDF

4. Natl. Org. Program (NOP). 2011. National Organic Program. Last accessed 2011-12-5. PDF

5. Brittan K. 2006. Methods to enable to coexistence of diverse corn production systems. Univ. Calif. Agric. Nat. Resourc., Agric. Biotechnol. Calif. Ser., Publ. 8192

6. Hutmacher RB, Vargas RN, Wright SD. 2006. Methods to enable coexistence of diverse production systems involving genetically engineered cotton. Univ. Calif. Agric. Natl. Resour., Agric. Biotechnol. Calif. Ser., Publ. 8191

7. Putnam DH. 2006. Methods to enable coexistence of diverse production systems involving genetically engineered alfalfa. Univ. Calif. Agric. Nat. Resourc., Agric. Biotechnol. Calif. Ser., Publ. 8193

8. Byrne PF, Fromherz S. 2003. Can GM and Non-GM crops coexist? Setting a precedent in Boulder County, CO. Food Agric. Environ. 1:258–61

9. Pew Initiat. Food Biotechnol. 2006. Peaceful Coexistence Among Growers of Genetically Engineered, Conventional and Organic Crops. The Natl. Assoc. State Dep. Agric. The Pew Initiat. Food Biotechnol. Boulder, CO. Last accessed 2011-12-5. PDF
Summary of workshop examining how growers of conventional, GE, and organic crops peacefully coexist and identified options on how to foster coexistence.

10. Comm. Eur. Communities. 2003. Guidelines for the development of national strategies and best practices to ensure the co-existence of genetically modified crops with conventional and organic farming. Brussels, Belg. Last accessed 2011-12-5. PDF

11. GMO Saf. 2010. Coexistence in the countries of the EU: A European patchwork. Last accessed 2011-12-5. PDF

12. Beckmann V, Soregaroli C, Wesseler J. 2006. Co-existence rules and regulations in the European Union. Am. J. Agric. Econ. 88:1193–99

14. GMO Saf. 2006. Coexistence to continue to be regulated by member states for the time being. Last accessed 2011-12-5. PDF

15. Dep. Environ. Food Rural Aff. (DEFRA). 2006. Consultation on proposals for managing the coexistence of GM, conventional and organic crops. Last accessed 2011-12-5. PDF

16. GMO Saf. 2011. Coexistence information system. Last accessed 2011-12-5. PDF

17. Assoc. Off. Seed Certifying Agencies. 2008. About AOSCA. Last accessed 2011-12-5. PDF

18. Bradford KJ. 2007. Methods to maintain genetic purity of seed stocks. Univ. Calif. Agric. Nat. Resourc. Agric. Biotechnol. Calif. Ser., Publ. 8189

19. Calif. Crop Improv. Assoc. 2007. About the California Crop Improvement Association. Last accessed 2011-12-5. PDF

20. Bayne S. 2006. Proposals for managing the coexistence of GM, conventional and organic crops. Biologist 53:285–86

21. Migus M. 2004. GMO Statutory liability regimes: An international review. Can. Inst. Environ. Law Policy, Dec.


Updated 2/16/12