Photo by Andreas Krappweis/sxc.hu.
This past winter I was asked to discuss twin-row corn as part of my presentation at a Delaware crops meeting. In twin-row corn, two rows of corn are planted 7 to 8 inches apart, with 30-inch spacing between the twin rows. The reason I was asked to include twin-row corn is that one of the local farmers had tried it and claimed that he got a big yield increase. One of the theories behind twin-row corn is that you can increase plant population because the sun can shine on both sides of the twin rows. Well, it sounds good anyway.
Fortunately, there have been literally hundreds of trials involving twin-row corn, comparing twin rows to corn planted in 20 and 30-inch rows. (A row width of 30 inches has become the standard, while corn planted with a 20-inch, and sometimes 15-inch, row width is referred to as narrow-row corn.) Unfortunately, the conclusion from these trials is that compared to 30-inch rows, it's just as likely that twin-row corn will result in lower yields rather than yield improvement.
John Deere published the results of about 40 trials, while DuPont Pioneer did 179 comparisons in 31 locations. Both arrived at the same result: On average, narrow-row corn yielded about 1 bushel per acre less than corn planted in 30-inch rows. Beck's Hybrids (a seed company) extensively studied twin-row corn at a wide range of plant populations. The conclusion: 30-inch rows outyielded twin rows at all populations, from 24,000 to 48,000 plants per acre, with the biggest differences at the higher populations.
Behold the turtle ...
There's plenty of evidence that corn planted in narrow rows usually yields more than corn planted in 30-inch rows, particularly in the northern half of the U.S. Therefore, it's logical that innovative farmers and equipment dealers would try other row spacing options in an attempt to further increase yields, including twin rows. One advantage of twin rows over narrow-row corn is that the twin rows can be harvested with standard 30-inch-wide chopper and combine heads. (This has become less of a limitation for corn silage producers, since many self-propelled forage harvesters now have heads that will harvest any row spacing.)
Twin-row corn represented a good attempt at increasing yields, but one that, so far at least, simply hasn't panned out. Not that twin-row corn is a complete failure, since in half the trials it resulted in a yield increase. Over time someone might figure out the reason for this and be able to recommend a set of conditions where twin-row would result in consistently higher yields. As the saying goes: "Behold the turtle. He makes progress only when he sticks his neck out." We should all thank innovative farmers and farm equipment engineers for pushing the envelope in planting and harvest equipment.
Another corn planting system that has never really caught on is ridge tillage. This consists of the formation of ridges in cornfields spaced 30 inches apart. Corn is then planted on top of the ridges, which often requires a corn planter modified for ridge planting, since a normal planter tends to slide off the side of the ridge.
Ridge tillage is a form of reduced tillage, and can reduce the soil erosion potential because of the resulting residue cover when corn is harvested for grain. Though research has shown that ridge tillage can be a good alternative to other forms of conservation tillage, this system has never become popular, especially in the northern U.S. and on dairy farms, where a high percentage of the crop is harvested for silage. Ten years ago, ridge tillage represented less than 5 percent of all U.S. corn acreage, and though recent data is hard to come by, the acreage doesn't appear to have increased much, if at all.
Ridge tillage certainly can work, and some farmers who have been using it for years are very pleased with it. However, while I get frequent questions on a variety of crop topics from farmers and other agricultural professionals, I can't recall the last time I got a question about ridge tillage. In general, the more equipment changes a farmer has to make to adopt a new technology or technique, the less likely it is that they'll do so, unless the results appear to be overwhelmingly positive.
We tried ridge tillage at Miner Institute about 20 years ago, comparing it to chisel plowing in the same 40-acre field. One advantage cited for ridge tillage is that the tops of the ridges warm quickly with the heat of the sun. However, we found that they also cool quickly at night, and at 8 a.m. the coldest soil in the field was at the top of the ridges! We also found that ridge tillage didn't fit our corn silage production system, since running across the ridges is a no-no. That meant that all equipment must enter and exit at the end of the row, which in the 40-acre field we ridged quickly became tedious, especially when the forage truck was full of chopped corn a quarter of the way down the field. Timing may not be everything, but during corn harvest it's right up there.
Localizing crop research results
The U.S. is a big country, and what works in one area may be an utter failure elsewhere. Soils, climate and farming enterprises all play a part, and the phrase "different strokes for different folks" certainly applies for crop production options. There can be a big difference between how a corn production technique "fits" in northern New York, where the frost-free season is 130 days or less and most corn is harvested for silage, and how it works in the southern Corn Belt, where the frost-free season is over 150 days and most of the corn is harvested for grain. Also, the fertilizer needs of crops are much different on dairy farms when compared to crop farms. The nutrient needs of the crop are similar, but on dairy and other livestock farms, much of the nutrients can be supplied by manure.
Ev Thomas has worked as an agronomist in New York for 45 years, first with Cornell University Cooperative Extension, then with the William H. Miner Agricultural Research Institute in Chazy, N.Y., including managing its 680-acre crop operation. He continues to work part-time for Miner Institute and is now an agronomist at Oak Point Agronomics. He has written our Forages column for 15 years and has been an expert contributor on a number of other topics.