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Insight 19

TWIN ROW CORN PRODUCTION - IS THERE A YIELD BENEFIT?

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A relatively recent modification of narrow row spacing is twin rows. Twin row planting has gained interested lately as a way to potentially capture the  benefits of narrow corn rows without any new machinery expenses besides the planter.

Figure 1: Across- and within-row spacing (in inches) in various row configurations at 36,000 plants/acre.

In a twin row configuration, corn is planted in paired rows usually 7-8 inches apart or 30-inch centers (Figure 1). This system provides a more uniform spacing of plants, similar to a narrow corn row, but allows a grower to use the same corn head and other equipment set for 30-inch rows. The minimum distance between plants in a twin row system is greater than that of 20-inch rows but less than that of 15-inch rows at the same population. Therefore, if maximizing space between plants is important to yield, twin rows would be expected to perform slightly better than 20-inch rows but not quite as good as 15-inch rows.

When studying the effects of twin row planting on corn growth and yields it is useful to also consider the extensive body of research conducted on narrow rows, particularly 15-inch rows, which provide a theoretically near-optimum spacing. Any benefits from a twin row system should be realized to a similar or greater extent in 15-inch rows.

Some newer twin row planters are capable of planting seeds in a precise alternating diamond pattern, increasing the minimum distance between plants (Figure 3). However, the advantage of the alternating pattern diminishes as plant population increases. For example, an alternating pattern increases minimum plant spacing by 1.9 inches at 36,000 plants/acre, but only 1.4 inches at 42,000 plants/acre. Any actual yield advantage of an alternating pattern relative to a parallel pattern remains unproven. Twin row research by Nelson and Smoot (2009) did not detect a yield difference between alternating and parallel twin row arrangements.

Figure 2: Distances (inches) between plants in alternating and parallel twin rows at 36,000 and 42,000 plants/acre.

Yield results of Twin Row Studies

Pioneer conducted on-farm research studies in 2010 comparing yield in twin and 30-inch rows. Most of the studies were conducted in Illinois, Iowa, and Minnesota; although side-by-side comparisons were also done in Colorado, Indiana, Kansas, Missouri, and Ohio. A total of 179 paired comparisons across 31 locations showed no overall yield advantage to twin rows over 30-inch rows.

[quote] A total of 179 paired comparisons across 31 locations showed no overall yield advantage to twin rows over 30-inch rows. [/quote]

These results are very similar to those of a Deere & Co. survey of twin row studies conducted between 1980 and 2008 in North America that also found that, on average, twin rows did not yield any greater than 30-inch rows. These results are similar to those observed with narrow-row corn. Yield increases with 20-inch or 15-inch rows have not been great enough or consistent enough to motivate growers across much of the Corn Belt to shift away from 30-inch rows.

Stalk strength and standability.

One question related to the potential yield benefit of twin row corn is whether the greater space between plants may allow thicker, stronger stalks resulting in improved standability at harvest. Research trials thus far have not demonstrated an increase in stalk diameter (Sorensen et al. 2006) or a reduction in stalk lodging (Foster and Watters 2006) in twin rows. Kratochvil and Taylor (2005) found that stalk rot and stalk lodging actually increased in twin rows relative to 30-inch single rows. The reason for this increase is unknown, so further research is needed; however, it does indicate that improved stalk strength and standability should not be considered a constant benefit with twin row corn.

[quote] Improved stalk strength and standability should not be considered a constant benefit with twin row corn. [/quote]

Potential Interacting Factors

The variation in yield response among studies with narrow row and twin row corn suggests that other factors are playing a role in determining yield. Plant population, hybrid, and field environment have all been discussed as factors that could influence any potential yield benefits of twin row spacing.

Plant Population. One of the most common questions about twin row corn is whether it will allow growers to increase yield by planting at higher populations than are practical in 30-inch rows. As plant populations increase, the space between plants within a row gets smaller, which has led to concerns that interplant competition may become yield-limiting in 30-inch rows at high populations. A twin row arrangement has been looked to as a way to alleviate this competition by providing more space between plants, thereby allowing growers to realize the full yield potential of modern hybrids.

Pioneer conducts extensive research on plant population in 30-inch rows. Though optimum plant populations vary among hybrids, many hybrid optimums routinely exceed 35,000 plants/acre, particularly in high-yield environments. The data clearly shows that corn yield can continue to increase in 30-inch rows at populations greater than 35,000 plants/acre. A Pioneer research study conducted in 2005-2006 compared twin, narrow, and 30-inch rows at high populations of 36, 42 and 48 thousand plants/acre. These studies showed no performance advantage of twin rows over 30-inch rows at high populations (Figure 3).

Figure 3: Corn yield in 30-inch rows and twin rows among plant populations included in Pioneer studies.

Pioneer on-farm trials in 2010 also found no effect of plant population on twin row yield performance relative to 30-inch rows (Figure 7). Twin rows and 30-inch rows were compared at 36,000 and 42,000 plants/acre at seven sites in Iowa and at 34,000 and 40,000 plants/acre at four sites in Minnesota and three sites in Illinois; none of which showed any significant interaction between row configuration and plant population.

University research conducted in 2003 and 2004 in Maryland and Delaware similarly found no evidence that plant population can be increased in twin rows to achieve higher yields than is possible in 30-inch rows (Kratochvil and Taylor 2005).

Hybrid. A common question among growers interested in twin row corn is whether certain hybrids are more suited to this system than others. Twin row studies that have included multiple hybrids have generally found no difference in response to row spacing. Pioneer on-farm twin row studies conducted in 2010 included several locations with multiple hybrids; some locations with as many as 10 hybrids. Among 14 current hybrids that were tested at three or more locations, no significant differences in yield between twin rows and 30-inch rows were observed, nor were any hybrid by row spacing interactions observed among hybrids compared at multiple locations.

Environment. Narrow and twin rows have been considered potentially advantageous in both yield-limiting and high yield environments. In environments limited by availability of light, water, or fertility, a more equidistant plant configuration should be more efficient in capturing these resources and increasing yield. Narrow or twin rows, then, would have less advantage in an optimal environment where all resources are available in abundance. Yet narrow and twin rows have also been promoted as a way to increase yield in extremely productive environments where all other yield-limiting factors have been adequately mitigated.

Other Twin Row Applications

Twin Rows in Corn Silage Production. Narrow row spacing has been consistently effective in increasing corn silage yield in studies conducted in northern Corn Belt states and the northeastern U.S. (Stahl et al. 2009). These studies mostly involved 15-inch rows however, which have been limited in adoption due to the difficulty of applying post emergence herbicides without excessive crop damage. Twin rows have generated interest in silage production due to the potential for increasing yields while maintaining the ability to conduct field operations in a standing crop. Limited research on twin rows in silage corn conducted to date has shown mixed results. A two-year study in New York (Cox et al. 2006) found that silage yield and profitability in twin rows was greater than 30-inch rows, but less than 15-inch rows. A one-year study in Ohio found no difference in silage yield or quality with twin rows (Foster and Watters 2006). Research conducted in Virginia in 2006 and 2007 found a 12.5% increase in silage yield with twin rows compared to 30-inch rows with similar silage quality. Given the track record of success with silage in narrow rows in some areas, however, twin rows may allow growers to gain some of the benefits of narrow rows without some of the inherent limitations and costs.

Conclusion

The extensive history of research on corn row spacing has repeatedly shown that it is a very complex issue with many interacting factors. Yield results have often been inconsistent and highly variable across environments, making it difficult for growers to determine the best solution for their individual farms. The same is true of twin row corn.  Pioneer twin row research conducted in 2010 reached the same general findings as previous university research on twin row corn. The accumulated body of research currently provides no indication that a transition from 30-inch rows to twin rows would provide a wide-scale yield benefit.  Nor is there consistent evidence that new hybrids and higher plant populations will broadly favor twin row production in the near future.However, ongoing research by Pioneer scientists will continue to explore the applicability of narrower row configurations with higher plant populations and new hybrids.

Twin row corn has gained interest as a way to potentially increase yields without some of the difficulties and costs of switching to narrow rows.

  • Pioneer conducted extensive on-farm research in 2010 comparing yield in twin and 30-inch rows.
  • Pioneer and university research studies have shown similar yields between twin rows and 30-inch rows; however, results at individual locations have varied.
  • Optimum plant population for maximum yield does not appear to differ significantly according to row spacing.
  • Research results do not indicate that growers need to switch to twin or narrow rows in order to increase seeding rates.
  • Pioneer and university studies thus far have not shown any significant differences in hybrid response to twin rows.
  • No consistent relationship between yield level and yield response to twin rows has been demonstrated.
  • Twin row corn may be a favourable option in silage corn production or where row spacing’s wider than 30 inches are currently being used.

 


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Revised: March 2017
Expires: March 2018