Soybean Planting Considerations: Planting Date, Seeding Rate and Row Spacing Implications

By Maninder Singh

Management decisions at soybean planting are critical in setting the crop for success. Soybean extension specialists from across the U.S. have been working together to summarize research related to various management practices. This effort has been funded by United Soybean Board. Data contributed from Michigan was generated based on research funded by Michigan Soybean Committee. Below is a short summary of what we found out regarding impacts of planting date, seeding rate and row spacing. For more information on impacts of these decisions in Michigan, please read our Michigan State University Extension article on soybean planting considerations.

Planting date

Timely planting of soybean is critical in achieving high soybean yields. Although early planting is important to maximize yield, planting into a wet seedbed can result in compaction and soil crusting which could reduce stand establishment and yield. In Michigan, we estimate a yield reduction of 7% when planting soybean on May 31 compared to May 1, with majority of decline occurring after mid-May.

Timely planting allows for soybean to maximize light interception and canopy photosynthesis, increase number of nodes and seeds per unit area, and lengthen the seed filling period. However, careful planning is required to minimize risks associated with early planting.

Read the detailed report on planting date

Seeding rate

Soybean plants are very flexible at adjusting to a wide range of plant populations. Soybeans branch out and can produce high yields even at relatively low plant densities. For normal planting dates in Michigan and across the Midwest, generally 100,000 to 120,00 plants per acre is enough to achieve maximum yield. A higher population density is needed as soybean planting is delayed into mid-June. Recommended seeding rates vary considerably, but are often around 25% higher than the target plant population.

Read the detailed report on seeding rate

Row spacing

Soybean row spacing used by growers varies widely across the U.S. In Michigan, most farmers plant soybean in 15- or 30-inch row widths. Across the U.S., narrow rows (≤ 15 inches) out-yielded wide rows (≥ 30 inches) 69% of the time. This is probably due to earlier canopy closure in narrow rows that enables more light interception and drives photosynthesis.

Read the detailed report on row spacing