Narrow Row Spacing in Corn: Management Considerations for Ohio

Optimizing corn yields involves considering various factors such as planting date, hybrid maturity, row spacing, plant population, and input levels (Ahmad et al., 2010). Growers, facing the challenges of variable weather, new technologies, and advanced genetics are continually seeking ways to enhance yields and improve operational efficiency, productivity, and profitability at the farm level. In recent years, these dynamics have led to some interest in producing corn (Zea mays L.) in narrow-row-spacing conditions. However, agronomic recommendations for the production of modern grain and forage hybrids using narrow row spacing are limited.

To address this issue, researchers from The Ohio State University conducted a series of trials to identify the various factors associated with improving narrow-row corn production. These factors included hybrid selection, population density, potential disease issues, and response to foliar inputs of nitrogen (N) and fungicide. The trials were conducted from 2016 to 2018 in two Ohio sites—South Charleston, western Ohio (a Kokomo silty clay loam with higher yield potential), and Hoytville, northwest Ohio (a Hoytville silty clay loam with lower yield potential). For all trials, the row widths studied were 30 inches (conventional) and 15 inches (narrow).

Hybrid Response to Narrow Row Spacing is Minimal, Though Yields Marginally Increased

Gomes et al. (2024) summarized work where four hybrids varying in relative maturity and drought tolerance were assessed (Table 1). All plots were seeded at 40,000 plants per acre at South Charleston and 36,000 plants per acre at Hoytville. To determine forage yield, six plants were harvested shortly after black layer and weighed (grain + biomass). The average biomass per plant (adjusted to 4% moisture) was multiplied by the final stands from each plot to determine total dry biomass production as a proxy for forage yield. The remaining plants in each plot were harvested mechanically using a narrow-row combine head (reported at 15.5% grain moisture).

Table 1 (click image to download Word doc). Hybrids names and their respective relative maturity grouping, drought tolerance rating, growing degree units to maturity, and relative maturity.

Response to row spacing was similar across hybrids—— interaction was not based on hybrid row spacing. Modest yield gains of 4% for grain and 11% for forage were observed for the narrow-row corn across the years (Figure 1). As expected, greater yields were produced at the high-yield-potential site in South Charleston (>200 bushels per acre for grain and approximately 10 tons per acre for forage).

Seeding Rates Should be Similar or Increase Slightly With Narrow Rows

For the population study, the objective was to assess the population response in narrow (15-inch) and wide (30-inch) rows in low- and high-yield-potential environments. One hybrid (P0506AM, Pioneer, Johnston, IA) was planted in narrow (15-inch) and conventional (30-inch) row spacing at three different seeding rates targeting 35,000, 40,000, and 45,000 seeds per acre. Measurements for forage and grain yield determination were performed as described in the previous section.

South Charleston showed a significant interaction of row spacing and seeding rate on grain yield (P=0.012), but no interaction or main-effect differences were evident at Hoytville (P=0.153) (Figure 2). This result showed that corn response to narrow row spacing and population was site dependent and, in this trial, was associated with the higher yielding environment. At South Charleston, yield was greatest in 15-inch rows at 45,000 seeds per acre (246 bushels per acre), which was about 3% greater than the 30-inch row spacing (240 bushels per acre). At Hoytville, the 15-inch-row corn produced greater grain yields than the 30-inch-row corn at 35,000 and 40,000 seeds per acre. However, at 45,000 plants per acre, the 15-inch-row corn yield dropped by 6 bushels per acre in comparison with the 30-inch-row grain yield.

Forage yield was not significantly affected by row width or seeding rate at either site (P>0.05). At Hoytville, forage yields ranged from 8.6 to 8.9 tons per acre in the 30-inch row, while forage yields in the 15-inch rows ranged from 8.9 to 9.6 tons per acre, with 45,000 plants per acre producing the highest numerical value in forage yields (Figure 2). At South Charleston, the highest numerical value in forage yields was produced by the 30-inch-row corn in all three plant populations, resulting in approximately 4% more yield than the 15-inch row.

Narrow-Row Production has Marginal Gains From Intensive Management

In a study by Lindsey et al. (2019), two hybrids (P0843AM and P0825AM) with similar relative maturity (108 days) but varying in foliar disease ratings, according to company literature, were used to assess differences in foliar disease and response to fungicide and foliar nitrogen (N) when grown in narrow (15-inch) or conventional (30-inch) row spacings. Foliar N treatments were applied at the R1 (flowering, full tassel) stage and included:

• untreated control
• N fertilizer applied at 5.9 pounds of N per acre (Coron 28–0–0 AG, Helena Chemical, Collierville, TN)
• application of the fungicide picoxystrobin + cyproconazole [2-(4-chlorophenyl)] at a rate of 1.43 + 0.57 ounces of active ingredient (AI) per acre (6.8 fluid ounces per acre of the product Approach Prima, Dupont de Nemours, Wilmington, DE)
• combination of foliar N (5.9 pounds of N per acre) and picoxystrobin + cyproconazole (1.43 + 0.57 ounces of AI per acre)

Partial return was included and calculated as the price received from grain yield at 15.5% moisture, minus both the drying discount and the cost of foliar treatment. In the absence of a fungicide, results showed that corn grown at 15-inch row spacing may benefit from a foliar N treatment, but the earnings from the yield gained could be similar to the cost of application (Table 2).

Table 2 (click table to download Word doc). Treatment [untreated versus foliar nitrogen (N) application] and row spacing interaction effect on corn yield, moisture, and partial economic return.

Despite the favorable environmental conditions for annual disease formation of either grey leaf spot or northern corn leaf blight, disease severity was low (3%–6%). When fungicides were applied, corn at the 30-inch row spacing was more responsive to foliar N than corn at the 15-inch row spacing (Table 3). The yield differences from the inclusion of N or fungicide may offset or slightly exceed the cost of application, but profitability will vary depending on the expected grain price, the cost of inputs, and application costs on an annual basis.

Table 3 (click table to download Word doc). Intensive foliar treatments [fungicide versus fungicide + foliar nitrogen (N)] and row spacing interaction on yield, moisture, and partial economic return.

Conclusions

These results suggest that modest yield gains of 3%–4% can be obtained from planting corn in narrow row spacings. However, such gains may not justify the potential increases of fixed and variable costs associated with the transition to narrow-row production, and these factors need to be considered. On the other hand, if a farmer has already transitioned to narrow-row corn production, planting a full-season hybrid and using increased seeding rates may be beneficial if farming in fields with high-yield-potential.

When considering foliar product applications, decision-makers should factor in current disease and nutrient levels, products and their associated application costs, and anticipated or contracted grain prices. In Ohio studies, yield gains were observed in narrow 15-inch rows when adding foliar N with no fungicide. When the foliar inputs included fungicide + foliar N, a yield response was not observed.

Note that the narrow row spacing tested in these studies was 15 inches between corn rows. Alternative row spacings are possible (e.g., 20 inches, 22 inches), as are alternative row configurations, such as wide row spacings (e.g., 36 inches, 38 inches, 60 inches) and/or 30-inch twin rows. Additionally, the introduction of short-stature corn hybrids may bring new opportunities and questions to be answered as it relates to row spacing configurations in Ohio and the region.

Acknowledgments

The authors would like to acknowledge the Crop Management Research Award program from Pioneer for its partial funding for these projects, as well as for its seed donations. Thanks also to Joe Davlin and Matt Davis (The Ohio State University Research Farm Managers) for overseeing the treatment applications and providing field support with planting and harvesting.

References

Ahmad, M., Khaliq, A., Ahmad, R., & Ranjha, A. M. (2010). Allometry and productivity of autumn planted maize hybrids under narrow row spacing. International Journal of Agriculture & Biology, 12(5), 661–667.
doi:10.2134/cftm2019.05.0039

Gomes, V. E. V., Lindsey, A., Novais, W., Thomison, P. R., Reese, K., Geyer, A. B., & Roth, G. W. (in press). Narrow row maize cultivation increased grain and forage yield of hybrids in Ohio and Pennsylvania. Agronomy Journal.

Lindsey, A. J., Thomison, P. R., Reese, K., Geyer, A. B., Ritchie, A., Banks, S., & Ogando do Granja, M. (2019). Does narrow‐row corn production influence plants’ response to foliar inputs? Crop, Forage & Turfgrass Management, 5(1), 1–7.
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