Remember 11 Sep 2001
Published at the Chat 'n Chew Cafe, 15 Sep 2001 (Updated 10 Oct 2001)

Transgenic Corn Harvest Reminders

R.L. (Bob) Nielsen
Agronomy Dept., Purdue Univ.
West Lafayette, IN 47907-1150
Email address:

Dirk Maier
Ag. & Biological Engineering Dept., Purdue Univ.
West Lafayette, IN 47907-1146
Email address:
NOTE: This article includes recommendations from a longer one originally published earlier this year (P&C Newsletter, 23 March 2001) and available on the Web as an Adobe Acrobat formatted publication at

Because certain transgenic corn hybrids (most notably glyphosate tolerant hybrids) are still not yet approved for overseas sales to the European Union, it is vitally important that growers of such hybrids remain keenly aware of the needs to a) segregate this grain and b) market it to approved end use channels. Segregation of transgenic and non-transgenic corn grain is also important for those growers who will market grain to certain grain processors that will not accept transgenic grain. Also recognize that grain elevators would prefer not to accept any transgenic corn that does not have full approval for the global market place and, subsequently, may change their stance on acceptance of such grain this fall.

Remember that glyphosate tolerant corn hybrids are approved only in the U.S. and Japan, but not elsewhere around the globe. Two transgene events currently exist for this trait, GA21 (original) and NK603 (more recent). Of the two, the GA21 transgene event is the predominant one used in glyphosate tolerant corn grown commercially by farmers in 2001. While a quick test kit for the detection of the newer NK603 event was recently announced by Strategic Diagnostics, Inc. (SDI) on 8 Oct 2001, no quick test kits currently exist for the more prevalent GA21 transgene event in corn (personal communication with SDI, 10 Oct 2001) and no tolerance levels have been established for either event. Even though some grain buyers are assuring farmers that they will purchase grain from these hybrids, farmers bear the sole risk for rejection at the first point of sale should buying policies change at any time in the future.

Harvest Operation. Combines should be super cleaned prior to the start of grain harvest to minimize the risk of any leftover grain from 2000 in the machine. If non-transgenic and transgenic varieties are grown on the same farm, then the sequence of harvesting those fields should follow the FIF-FOF (First-In-Field, First-Off-Field) principle. This means that non-transgenic varieties planted in the field first should be harvested before transgenic ones to avoid transgenic grain commingling with non-transgenic grain from the nooks and crannies of the combine.

Additionally, where transgenic and non-transgenic fields border each other, growers should strive to harvest areas of non-transgenic fields located within about 660 feet from the adjacent transgenic field and segregate the grain from that harvested from the remainder of the non-transgenic field in recognition of the possibility for pollen drift contamination from the adjacent transgenic field. The recommended 660 feet buffer zone is that typically used by the seed industry for minimizing contamination of seed production fields.

This buffer zone distance includes any non-cropland (roadways, ditches) that may separate two fields and is especially appropriate for non-transgenic fields that lie to the east or north of transgenic fields because of the usual prevailing winds in Indiana during pollination. If growers are certain that adjacent fields were NOT pollinating at the same time, then the buffer zone may not be necessary.

Handling, Storage & Transport. All grain transport vehicles (trucks, wagons, trailers, grain carts), all grain handling equipment (augers, legs, pits, wet holding bins, dryers) and all grain storage facilities should be super cleaned prior to the start of grain harvest. By following the FIF-FOF principle during harvesting, the post-harvest operations will benefit because non-transgenic varieties can be received, dried and transferred to storage ahead of transgenic varieties. Obviously, transgenic and non-transgenic grain should be stored separately on-farm to avoid grain commingling, and to take advantage of potential premiums for identity-preserved grains in the market place.

Assuming that transgenic grain was put into storage last, then emptying storage facilities for transport to market should begin with the transgenic grain in order to avoid an extra cleaning step, and thus, reduce the chance of contamination. However, given that this strategy will depend on a farmer’s marketing plan, all grain transport vehicles and grain handling equipment should be super cleaned prior to every time that non-transgenic grain load-out follows transgenic load-out in order to avoid commingling of grain leftover from the previous handling operation.

Grain Channeling. Be aware that Monsanto has established a channeling program for glyphosate tolerant corn. When buying glyphosate tolerant corn seed, farmers commit in writing to market the grain from these hybrids only through approved channels. We urge all farmers to live up to this commitment! Approved channels include:

Over 2000 U.S. elevators are willing to buy non-EU approved grains. The American Seed Trade Association (ASTA) maintains an online database of “… grain handling facilities that have indicated a willingness to purchase, receive, and handle genetically enhanced corn products that have full U.S. registration for food and feed use, but are not yet approved for import into the European Union.” The Web address for the ASTA database is

Be aware that Monsanto, as part of their channeling program, is also establishing a database of every farmer who purchases glyphosate tolerant corn seed. Although they have committed not to reveal names and addresses, they will work with any inquiring processor and reveal to them how many acres of glyphosate tolerant corn were planted in the areas from where they plan to purchase corn. For any area that a processor raises concern, Monsanto will contact those farmers and remind them to market their corn only through approved channels after harvest. We urge processors to inquire about glyphosate tolerant acres and urge all farmers to comply with the channeling program!


American Seed Trade Association. December 2000. Grain Handlers Database. On the Web at: (URL verified 13 Sep 2001)

Iowa Grain Quality Initiative. 2001. GMO Grain Testing Directory. On the Web at: (URL verified 13 Sep 2001)

Monsanto Company. 2000. Grain Channeling Information. On the Web at: (URL verified 13 Sep 2001)

Nielsen, Bob and Dirk Maier. 2001. GMO Issues Facing Indiana Farmers in 2001. Purdue Univ. Cooperative Extension Service Publication GQ-46. On the Web at: (URL verified 13 Sep 2001)

Wiebold, B. 14 Sep 2001. Segregated Marketing of Grain from Glyphosate Tolerant Corn. Integrated Pest & Crop Management Newsletter. University of Missouri-Columbia . On the Web at: (URL verified 13 Sep 2001)

KingCorn.orgFor other information about corn, take a look at the Corn Growers Guidebook on the World Wide Web at

It is the policy of the Purdue Agronomy Department that all persons shall have equal opportunity and access to its programs and facilities without regard to race, color, sex, religion, national origin, age, or disability. Purdue University is an Affirmative Action employer. This material may be available in alternative formats.
© 2001, Purdue University
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