Once soybeans progress past the vegetative growth stages is there anything growers can do to increase their yield as the crop matures?
That’s a question Syngenta Agronomic Service Representative Doug Fotheringham often gets throughout the growing season. “Many growers feel strong yields are ultimately tied to timely rains in July and August, but there are a lot of management opportunities to influence yield throughout the season,” he says.
Your first opportunity to impact yield starts with stand establishment, says Fotheringham. “Fifty to seventy-five percent of your yield is on the bottom of the plant. That’s mostly generated from stand establishment and keeping the crop healthy through the vegetative period.” At V1, growers should have uniform plant spacing and minimal gaps within the row. “That’s something that we can control. If we do all of those things up front and capture some weather events on the back half of the season, then that yield potential is there.”
Herbicide and fungicide timing is key
Timing herbicide application is another factor that can impact yield. When it comes to weed control, it’s important to keep fields as clean as possible. “Soybeans are very tolerant to glyphosate so it is ideal to get their second pass of glyphosate done before canopy closure,” notes Fotheringham. “It’s ideal to get those applications out of the way as early in the plant life cycle as possible.”
Late herbicide applications, especially when topping up with a contact herbicide, can stall soybean growth, reduce pod fill and ultimately, yield. “The first three weeks in June are extremely important because those are our longest, hottest days of the season. We want those beans to be fully and actively growing throughout that time period to capture as much energy and sunlight as possible,” explains Fotheringham.
Making effective disease management decisions will also help growers put more beans in the bin. When it comes to managing a disease like white mould, it’s important to keep an eye on both plant population and canopy closure to properly time fungicide applications. “With high plant emergence comes a denser canopy. That becomes even more problematic if you have some moisture,” says Fotheringham.
Because white mould and other diseases tend to be based at the bottom of the plant, it’s important to be aware of your population and canopy development to effectively time application. “If you want to influence pod fill, you have to get in there before the row closes to suppress that disease,” says Fotheringham.
Scout for pests and beneficials
Scouting for insects can provide a positive return on investment. To detect aphids, for example, growers need to be scouting fields from the R1 to R3.5 stage. Dry, hot conditions are conducive to aphid reproduction. Spraying based on economic thresholds can reduce the impact of these yield-robbing pests, but late detection can be costly – once the crop reaches R4 to R5, insecticides are relatively ineffective on this pest.
Fotheringham notes that beneficial insects are the number one defense against aphids, so growers need to factor in the health of these friendly bugs when deciding whether to spray an insecticide. “Beneficials such as lady bug larvae are fantastic on aphids and easy on the pocketbook, so it’s important to assess these populations and factor them into your management decision.”
Watch for nodulation
Evaluating nodulation also gives growers an opportunity to enhance pod fill and yield. Nodulation on roots is critical for the plants to fix nitrogen. Nodules can typically be detected at the third trifoliate. “The more the merrier,” says Fotheringham who notes that nodules have a deep pink colour when they are actively fixing nitrogen. “If they are brown or green colour inside, it just means they haven’t started working yet – I would come back in a few days to see if they’ve kicked into high gear.”
If no nodules have formed by the R3 or R4 stage the problem is likely high residual nitrogen in the field or inoculant failure. In these cases, growers can consider a top-dress nitrogen rescue treatment, but it’s important to get to the root cause. If it’s a nitrogen or micro-nutrient problem, that’s best fixed in the spring or fall,” adds Fotheringham.