If corn planting progresses at a rapid pace, many farmers will be asking if it is too early to make the switch to soybeans. In Iowa, should you plant beans in late April or the first week of May if the weather conditions and soil conditions permit doing so? Or should you hold off until the second week of May—maybe after May 10 or so?
The answer is "no"—don't hold off. That's the advice from agronomists at Pioneer Hi-Bred. The seed company's research data indicates from mid-to-late April is an ideal time to plant soybeans—if weather and soil conditions allow. Early planting is a key component in maximizing yields, points out Alex Woodall, Pioneer account manager in north central Iowa. Early planted beans are able to use a larger portion of the summer's total sun and heat energy.
Research in Iowa generally shows soybeans tend to suffer little yield loss from planting delays until after the middle of May. But to capture full yield potential, you have to plant earlier than that—if soil and weather conditions allow, Pioneer agronomists advise.
Planting early doesn't guarantee high yields, but it does boost the potential
The key components that make up soybean yield are: number of pods per plant, number of seeds per pod and the size of seeds in the pods.
Thus, the first key is to maximize the number of pods per plant. How can you maximize the number of potential pods? Soybean pods only develop on plant nodes. Research shows that the only way to maximize the number of nodes on a soybean plant is to plant early. "Planting soybeans early does not guarantee high yields but it does allow us to set the table for maximum production if we have good growing conditions the remainder of the growing season," he notes.
Pioneer agronomists say soybeans should be planted "in late April or as early in May as possible when soil temperatures are steadily increasing." But, they also caution that you should not rush the planting if soil conditions are not fit. If soybeans are planted under poor growing conditions, they will be more susceptible to early season diseases.
What are the optimum soybean seeding rates you should use?
Many farmers have lowered their soybean seeding rates over the past several years. They no longer plant as many seeds per acre as they used to. Pioneer agronomists say recent research suggests some farmers may have gone a little too low in their plant populations. True, soybean plants are adaptable to lower plant populations by increasing leaf area and branching out. Also, lower soybean plant populations have proven to offer competitive yields.
However, if you want to capture that last bushel of potential yield, you have to have enough plants per acre in the field to do it. Capturing that last bushel is more important today than it was just three years ago, notes Woodall. Another benefit is that the higher plant populations cause soybean plants to grow faster, making them more competitive with troublesome weeds--like waterhemp. Pioneer has some charts they show growers, which compare how optimum economic seeding rates increase with the commodity price of soybeans.
What about that early weed competition? How much yield are you losing?
While the calendar date determines when most of the crop is planted, weeds don't have a calendar. This year's early spring-like weather in March and April has given weeds a head start over the young corn and soybean crops. While today's herbicides can kill large grasses and give you the appearance of clean fields, farmers do not see the "lost" yield potential at harvest. University data continues to show that controlling weeds early in both corn and soybeans is critical to obtain maximum yield.
How much yield are you losing to early weeds in corn and soybeans? In corn, Missouri University research indicates with weeds that are 2 inches to 5 inches tall in a field of young corn, yield loss is in the 6% to 12% range. Iowa State University research indicates with weeds that are 2 inches to 4 inches tall, the yield loss is in the 5% to 9% range. Yield loss begins as early as the V2 growth stage of corn.
In soybeans, the university research indicates 4 inch weeds will equate to a 7% yield loss. And 12 inch weeds in young soybeans equated to a 15% to 25% yield loss.