Row Width
Soybeans thrive under a wide range of row widths, especially in the long-season regions of Ontario. Row width selection is influenced by numerous factors, including tillage system, equipment suitability, weed problems, soil conditions, white mould pressure, and planting date. In Ontario, the majority of soybeans grown are solid seeded (19 cm or 7.5 in. spacing) or intermediate row widths (38-56 cm or 15-22 in.). Planting in wide rows (76 cm or 30 in.) is becoming more common, especially in fields with a history of white mould outbreaks. In wider rows, improved air movement can help to reduce the severity of white mould. Lower seeding rates are also possible in wide rows.
Wide rows allow inter-row cultivation for organic production and are less impacted by soiling crusting. In wide rows, in-season weed control is more challenging due to an increase in late emerging weeds. In cool years or when planted late, wide rows will yield less than narrow or intermediate rows, especially in northern climates. Narrow rows allow the crop canopy to fill in more quickly, providing maximum light interception and weed suppression. The amount of solar radiation (sunlight) captured early in the season has a significant impact on yield. In southern Ontario, solar radiation levels drop off quickly after the middle of July. Therefore, it’s important to have full canopy closure by early pod set to maximize yields. Table 1, Row Spacing vs. Days to Full Canopy shows relative time differences in canopy cover. Rapid canopy development often means narrow rows need one less in-season herbicide application.
Table 1. Row Spacing vs. Days to Full Canopy
| Row Spacing | Days to Full Canopy | |
| Planting Before May 15 | Planting After May 15 | |
| 18 cm (7 in.) | 30 days | 25 days |
| 38 cm (15 in.) | 45 days | 40 days |
| 51 cm (20 in.) | 55 days | 50 days |
| 76 cm (30 in.) | 70 days | 65 days |
Some producers using wide rows have exceptional yields. Wide rows are well suited to rich soils where beans grow tall and lush. When planting in wide rows, choose bushy varieties, seed early and conduct some form of tillage, especially within the row. Strip-tillage is a practical way to gain the benefits of tillage within the row, while maintaining crop residue between the rows. These practices will help to fill the canopy as soon as possible, minimizing possible yield losses associated with wide rows. Planting wide rows late can lead to significant yield reductions.
On heavier soil types, emergence will be aided with wider row widths which increases the number of seeds per foot of row, see figure 1. On clay soils prone to crusting, a minimum row width of 38 cm (15 in.) has shown better emergence than solid seeded beans 19 cm (7.5 in).
Figure 1. Soybean seedlings working together to break through a soil crust.
Another advantage of wide rows is that lower seeding rates can be used resulting in significant cost savings. Also, a single planter can be used for both corn and soybeans reducing the need for a seed drill. There is also less sprayer tramping later in the growing season.
Although yield losses to wide rows are greatest in northern areas, as shown in Table 2, Effect of Row Width on Yield, there is still a yield advantage to reducing row widths to less than 53 cm (21 in.) in southern Ontario. Row widths of 38 cm (15 in.) have gained popularity because they allow a reduction in seeding rates when compared to 19 cm (7.5 in.) rows while still providing excellent yield potential. They also make it possible to use planter row units, increasing seed placement accuracy. In short-season areas, narrow rows increase yields across a range of soil types and growing conditions, mainly because plants fill the canopy more quickly. For much of Ontario, an intermediate row width of 38 cm (15 in.) is a good compromise between the higher yield potential associated with narrow rows and the advantages of more air movement in wide rows. In fields with a history of white mould a minimum row width of 38 cm (15 in.) is recommended but 76 cm (30 in.) is ideal.
Table 2. Effect of Row Width on Yield
| Soybean Row Width | Yield1 |
| 18 cm (7 in.) | 3.3 t/ha (49 bu/acre) |
| 36 cm (14 in.) | 3.2 t/ha (47 bu/acre) |
| 53 cm (21 in.) | 3.0 t/ha (45 bu/acre) |
| 71 cm (28 in.) | 2.7 t/ha (40 bu/acre) |
| 1Values are based on research on clay loam soils in a 2.8 MG area. Greatest response would be anticipated in shorter season regions. | |
Due to the inherent advantages to wide rows various strategies can be used to mitigate the yield loss associated with 76 cm (30 in.) rows. One 6 site-year Ontario study tested the use of starter N, foliar fungicides, and early planting as strategies to “win back” the yield loss associated with wide rows. Although there was still a yield loss to wide rows, starter nitrogen fertilizer and the application of a foliar fungicide reduced the yield gap of 76 cm (30 in.) rows to only 1.3 bu/ac for the first planting date and 2.2 bu/ac for the second planting date, see Table 3, Soybean Response to Starter N and Foliar Fungicides in Wide Rows.
Table 3. Soybean Response to Starter N and Foliar Fungicides in Wide Rows.
| Row | Treatment* | Seeding | Planting** | Yield | Loss of 30 inch rows | |
| Width | Rate | Date | bu/ac | Compared to Untreated 15 inch rows (bu/ac) | ||
| 15″ | Untreated | 165 | Early May | 78.0 | ||
| 30″ | Untreated | 140 | Early May | 74.3 | – 3.7 | |
| 15″ | N | 165 | Early May | 78.4 | ||
| 30″ | N | 140 | Early May | 74.9 | – 3.1 | |
| 15″ | N + Fungicide | 165 | Early May | 80.4 | ||
| 30″ | N + Fungicide | 140 | Early May | 76.7 | – 1.3 | |
| 15″ | Untreated | 165 | Late May | 73.4 | ||
| 30″ | Untreated | 140 | Late May | 69.1 | – 4.3 | |
| 15″ | N | 165 | Late May | 72.8 | ||
| 30″ | N | 140 | Late May | 70.6 | – 2.8 | |
| 15″ | N + Fungicide | 165 | Late May | 76.7 | ||
| 30″ | N + Fungicide | 140 | Late May | 71.2 | – 2.2 |
*N = 10 gallons/ac of 28% UAN applied on soil surface at planting streamed on the row in 2022. 87 lbs/ac of urea broadcast in 2023. Fungicide = DELARO Complete at growth stage R2.5. A difference of less than 0.09 t/ha (1.4 bu/acre) is statistically insignificant.
**Early May = the first planting window when the soil was fit. (May 7-16) Late May = (May 30 – June 2).
Seeding Equipment
Table 4, Seed Drill vs. Planter Unit Yields, shows the yield impact of solid seeded drilled stands (19 cm or 7.5 in.) versus intermediate rows using a seed drill. Intermediate rows, established with planter units were also compared in these trials. The planter unit in 38 cm (15 in. rows) yielded 3.5% (0.12 t/ha or 1.8 bu/acre) more than the drill in 38 cm (15 in. rows). Additionally, the planter also yielded 0.7 t/acre (1.1 bu/acre) more than the 19 cm (7.5 in.) drill. Higher yields are seen with a row unit because seed placement is improved, which produces a more uniform plant stand. These trials also showed an overall plant stand advantage when soybeans were planted compared to being drilled.
Table 4. Seed Drill vs. Planter Unit Yields
| A difference of less than 0.27 t/ha (4 bu/acre) is statistically insignificant. | |||
| Comparison | Row Spacing | ||
| Drill 19 cm (7.5 in.) | Drill 38 cm (15 in.) | Planter 38 cm (15 in.) | |
| Yield | 3.28 t/ha (48.9 bu/acre) | 3.24 t/ha (48.2 bu/acre) | 3.36 t/ha (50.0 bu/acre) |
| Plant Stand at 30 Days after Seeding | 72.6% | 74.6% | 79.8% |