Written by: Bryce Rampton, Syngenta Product Development Agronomist
When seeding soybeans this season it’s important to keep an eye on harvest.
Many spring management decisions will have a big impact on whether you reach your yield goals and determine how many bushels make it to your bins this fall. One thing you can do to protect yield is take steps to ensure soybeans pod higher on the plant. This will limit harvest loss when combines start rolling.
Our goal is to have soybean plants set the first node on the plant at least three inches above the ground. This allows the combine cutter bar to slide beneath those pods and ensure the beans get in the bin. It’s important to remember that harvest losses can add up in a hurry — it’s easy to leave two to four bushels on the ground when we’re smashing through low-hanging pods.
Let’s take a look at the math. Losing four soybeans per square foot behind the combine is equal to one bushel of grain loss per acre. Also consider the fact that those first nodes on the plant are some of the most productive and the ones most likely to produce two or more pods.
Seeding environment impacts pod height
When it comes to pod height, the first management consideration is seeding environment. Planting into warmer soils promotes strong germination and emergence, helping plants ‘pop’ out of the ground. In this case, the cotyledon has strong extension and pushes the unifoliate upward, which leads to a higher set for the first node on the plant.
The opposite happens when we plant into cold, wet soils and cooler conditions. It’s also important to avoid compacted or saturated soils — in both situations the plant uses up significant resources for plant emergence and that first node tends to be lower.
The extension height to that first node is really determined by how it comes out of the ground. If it stops short above the ground — i.e., if the cotyledon doesn’t extend and push the unifoliate up — it’s going to set the first node lower and those pods will be closer to the ground.
Plant into warming trends
Planting into dryer soils can also affect node height as the plant is often impacted by drought stress. Whether environmental conditions are cool and wet or if moisture is in short supply, early planting is tempting because there is a strong correlation to higher yields. When conditions are poor, however, many agronomic factors can suffer, including pod height. It’s always better to keep an eye on the weather, and if possible, plant into warming trends.
Many growers ask if genetic variation plays a role in pod height. Overall, there is some variation between varieties, but agronomics and soil environment have a greater impact. One agronomic factor that should be considered is plant population. Higher populations help maximize emergence because plants are closer together and they tend to push out of the ground together. They have the same growth profile and combine efforts to push the soil and emerge faster. But don’t bump up your populations just to help the plant pod higher. It’s important to consider risks associated with higher populations such as lodging and diseases like white mould.
Planting depth and rolling
Growers also have to be mindful of soil compaction at planting. When you have a high level of soil moisture, keep an eye on the amount of down force on the planter. Compacting the soil will cause the seed to use too much energy pushing to the surface and compromise its early growth.
Planting depth is another one to watch. For the last couple of years growers have been chasing moisture. Remember, deep-planted seed will draw heavily on energy reserves to reach emergence; if you have a rainfall event or if you farm high-density clay, you could be making it difficult for those beans to emerge. Be sure to vary planting depth based on soil type and be aware of forecasted weather events when you plant.
The final consideration is rolling. You can’t always make plants come up higher, but you can try pushing down the soil. Rolling is certainly one way to increase the distance between the soil and that first node, especially if you have rocky soil or root balls remaining from a corn crop. Push them into the ground — it will make soybean harvest more manageable in the fall.