When getting ready for the upcoming seeding season, growers often ask our representatives what their seeding rate for the soybeans should be. Many factors influence the seeding rate, chiefly the soybean variety, expected yield, soil type, equipment used and history of disease. Here’s a guide that will shed some light on those elements.
Based on the target population measured in seeds/ha or seeds/ac (see the Prograin Seed Guide), first determine the seeding rate in kg/ha or lb/ac using the seed size indicated on the bag or the weight of the bags of seed. Either use the imperial or metric measurements, but don’t mix them. Here’s an example of calculation.
Now, let’s take a closer look at the factors that may affect the seeding rate.
- Experience of the grower or advisor → How knowledgeable they are about their land’s productivity and the region.
- Variety → Some varieties thrive better in a higher or lower plant population environment. Later maturity varieties tend to grow into bushier plants than early maturing varieties. As a consequence, late varieties may require a lower seeding rate.
- Seed treatment → When using a fungicide that will coat the seeds, reducing the seeding rate by 5 to 10% might be suggested.
- Use of a foliar fungicide → This type of fungicide allows the seeding rate to be maintained for maximum potential yield.
- Row spacing (narrower or wider): when using wider row, lowering the population is recommended to reduce competition amongst plant on the row. This will help to maintain their health.
- Soil fertility → In a very fertile soils with great potential yield, the seeding rate can be reduced by up to 10%.
- Soil type → Because of its impact on plant emergence, a sandy soil may warrant an almost 10% reduction of the seeding rate and a loamy soil, a 5% reduction. In clay soils, however, the seeding rate should be maintained.
- Seeding management → The seeding rate remains the same with no-till seeding but is reduced by 10% with conventional seeding.
- Type of planting equipment → Planter vs seed drill, with the planter maintaining a more consistent depth. By using a planter, the seeding rate could be reduced by 5 to 10%, because the seeded population = target population.
- Seeding date → When seeding early, such as during the first week of May, you can reduce the seeding rate by 5% if the temperature remains above 10 degrees in the following days, whereas when seeding later, let say starting on June 5, we recommend increasing the seeding rate by 10%. You must also reduce row spacing when seeding late.
- Crop rotation → Corn/soybeans or soybeans/soybeans. Consider increasing the population by 5 to 10% if large amounts of corn residues remain.
- Amendments → Adding manure or fertilizer to the planter allows to reduce the population by 10%.
- Region → North vs South. In northern areas, we recommend seeding more (+5%) and reducing spacing between the rows.
- Production method → Organic vs conventional. When using organic production methods, some growers like to seed more to ensure a good plant/acre ratio in case the row crop cultivator pulls some plants.
- Reassurance → Some growers like to maintain a high population to protect against a potential freeze-up in spring.
In the end, at Prograin, we recommend aiming for 2 million nodes per acre, or 200,000 plants/acre for 10-node plants; 165,000 plants/acre for 12-node plants; and 130,000 plants/acre for 15-node plants. Do you have more questions about the seeding rate? Contact your Prograin representative today!