In Manitoba, the weather has warmed up and our soybeans are kicking into gear. They’re gaining some height and their dark green colour has returned, indicating that the plant roots are nodulating and making their own nitrogen. Many of our @StalkOption fields are flowering, and other fields are beginning to pod.
Soybeans have incredible yield potential. In 2010, when one of our agronomists was walking a drowned out field in Manitoba, he found an amazing rogue plant. It was growing on its own without any competition, so it had all the room it wanted to bush out. This plant had 208 viable pods, and some nodes had up to nine pods!
You’ve probably heard my fellow #StalkAgvisor @MikeFolkard talk about the importance of reducing stress on soybean plants. You can really see the effects of stress during the flowering stage. Soybeans bloom steadily until daylight hours shorten in mid-August. If the plant experiences stress during that period, it will abort flowers and instead focus on developing remaining flowers into fruit. After that, any additional stress can cause the plant to abort pods or seed. That’s when we will see pods with no seeds or missing seeds.
There are dozens of different stressors that can take away from soybean yield potential, which is why plants growing under normal field conditions don’t pod up like the rogue in the drowned-out field. Soybeans typically have between 30-50 viable pods with three to four pods per node.
One of the most common stressors at this stage is moisture. Now that the soybeans have kicked their growth into high year, they need water to support their vegetation.
While it seems like we have had nothing but excess moisture this year, the sudden onset of high temperatures will dry out fields very quickly. We’ll need a good rain in early August to support soybean pod development. Farmers who seeded in narrow rows can hold out for rain longer than farmers who seeded in wide rows, as thick vegetation does a better job holding moisture in the soil.
Last year, soybean farmers in Manitoba took a 10% hit in yield because of lack of moisture. We didn’t get the rain we needed at the end of July and early August. Many soybeans crops had empty pods and poor seed set (e.g. missing one seed out of three in a pod).
There are many factors that contribute to seed set, including nutrient availability, sunlight, heat units and insect, disease and weed pressure. A Cargill agronomist can help you assess your field and determine what stressors are separating your soybeans from their yield potential.