Boost soybean yield by planting early
Soybean planting is trending earlier, particularly on farms where growers have a planter dedicated to soybeans. University surveys of growers attribute maximizing yield potential and avoiding delays due to weather as reasons for earlier planting dates.
The ideal planting date will vary based on geographic location, but research indicates that timely soybean planting is important for optimum yields. Yield increases from earlier soybean planting dates can be attributed to the timing of soybean development stages and day length. Soybeans obtain higher yields when their critical developmental stages occur during periods when the day length is longer. The crop converts sunlight to energy, producing more nodes, which increases the potential for greater pod and seed numbers.
The soybean canopy should be closed by the R1 reproductive stage (beginning flower) in order to obtain the optimum photosynthetic potential. Optimum seeding rates and narrower row spacings are considerations that can improve the speed of canopy closure and boost yields.
After soybeans have emerged, all growing points are above the soil surface and susceptible to frost injury. Therefore, it is generally recommended that soybeans in the Dakotas be planted no sooner than five days before the average killing frost to reduce the chances of stand loss due to spring frost.
The average dates with a 50% probability for a killing frost are shown in the map below. This information, along with a keeping close eye on the weather and soil temperatures, can help with planting decisions. Soil temperatures need to be at least 50 degrees F at the time of planting, with a warming trend in the short-term forecast in order for soybean seeds to germinate and emerge successfully.
Recent research has shown that soybeans can tolerate a reasonably wide window of planting dates and still produce top yields. However, outside the optimum window, yields are significantly lower and less stable. South Dakota State University research found soybeans planted at an early planting date of May 5 achieved higher yields than those planted in late May, with the optimum planting dates between May 5 and 25. In North Dakota, the ideal planting dates to avoid frost injury and maximize yield potential are between May 10 and May 25.
Although research has indicated benefits for planting soybeans in early May, it has its risks. Planting before the crop insurance date can be risky and is often not recommended. It is important to be aware of insurance dates in your state.
Unfortunately, conditions do not always allow for early planting, and growers are forced to plant later. However, there is some good news if you have to plant soybeans later than you would prefer.
Regardless of the variety’s maturity, soybeans have the ability to adjust their physiological maturity to the daylight hours. If planting is delayed three to five days, flowering and maturity are only delayed about one day. If the same variety is planted 30 days later than ideal, its maturity is only delayed by seven to 10 days, not a full 30 days.
If planting is delayed to June 10, switching to an earlier-maturity-group variety is recommended. With later planting, reconsider management practices to maximize yield.
Stay with full-season maturities for your area, unless planting is severely delayed (later than June 10).
If planting after the first week in June, increasing the seeding rate by 10% is suggested, and planting in narrower rows may hasten canopy closure by R1.
Delayed planting might mean that harvest is delayed, leaving fewer available days for harvest.
Keep in mind: Because of earlier planting and higher levels of crop residue on fields, soils are generally colder and wetter at planting, and seedling diseases are more likely. Consequently, more growers are seeing an advantage from fungicide seed treatments that provide multiple modes of enhanced protection against a broad spectrum of early-season diseases, including rhizoctonia, fusarium and pythium. In addition, adding an insecticide to the treatment reduces the insect feeding that provides an entry port for disease infection.
Spring freeze median date of last 28-degree F freeze, 1981-2010 average
• March 10 or earlier
• March 11-20
• March 21-31
• April 1-10
• April 11-20
• April 21-30
• May 1-10
• May 1-20
• May 21-31
• June 1-10
• June 1-20
• June 21 or later
Median date is determined such that half of all the years fall before, and half fall after, the median date.
This article published in the April, 2014 edition of DAKOTA FARMER.
All rights reserved. Copyright Farm Progress Cos. 2014.