The concept is simple enough. Just modify your standard 30" corn planter to plant two rows instead of one row as shown in the picture below.
The theory behind this is to give each plant more room to capture sunlight because they are not as crowded as they would be if they are all crammed together in one row. This is to have a more positive yield effect as we increase plant populations.
(Excuse me for a second while I digress. I believe this is why the concept keeps getting re-cycled. When I began my career 28,000 population was considered high, now we are talking 36,000 plants per acre. At every incremental step over the years, somebody tries to prove the value of twin rows.)
At a plant population of 36,000 the space between plants is 5.8 inches as shown in the schematic diagram below.
Using twin rows 8" apart centered on 30", the interplant spacing for 36,000 poulation is 9.9" to 11.6". This is almost double the room for each plant in the the twin over the single row. Common sense tells us this should result in healthier plants and more yield.
But I know that common sense and corn plants do not always agree, so what does the research tell us?
Both Pioneer and John Deere looked at this concept in 2010. They co-operated together on some of the trial locations. Pioneer likes to sell seed and John Deere likes to sell equipment, so it is reasonable to conclude they would be interested in the concept and it is also reasonable to conclude they would both be interested in a positive research outcome.
Both companies came to the same conclusion.
In 31 locations across the corn belt in 2010, Pioneer found the overall advantage to 8" twin rows over 30" rows to be negative .7 bu/acre.
John Deere reviewed the scientific literature on twin rows from 1980 to 2008 and discovered a .7 bu advantage in favour of twin rows. Hardly a rosy picture for those that believe in the twin row concept.
And as my friend, Peter Johnson, said at the Southwest Ag Conference, "combining twin rows at night, with all those tassles jiggling in front of the cab will make you want to quit farming".
So my friend was not asking a dumb question after all. It was just a question that has been asked many times before.