STUesday-Tips for High Soybean Yield

Early Planting Tends to Deliver Higher Soybean Yields

Choosing when to start planting may be one of the most important decisions soybean growers make each year. In general, planting earlier than tradition sets the crop up for higher yields. Unfortunately, no 2 years are the same: Planting early offers potential rewards and potential risks.

“Planting date is key,” says Dan Poston, DuPont Pioneer agronomy research manager in the southern U.S. “The effect is real and demonstrable.”

Data from DuPont Pioneer Product Knowledge Plots from 1996 to 2012 show yields trend higher with April plantings then decline progressively with later planting dates. However, geography makes a difference: The farther north your location, the more risk with early planting.

Regional Differences

“Regional climatic conditions make response to early planting much less consistent,” Poston says. “In Arkansas, Louisiana and Mississippi, where soil temperatures are warmer compared to more northern latitudes, an almost linear decrease in soybean yield from April to later dates generally occurs. In Missouri, Illinois and Iowa, the trend is similar, but the rate of decline with later planting dates slower: Noticeable yield differences don’t occur until late May.”

Wisconsin, Michigan and Minnesota must deal with a shorter growing season (and plant very early maturity groups), resulting in dramatic reductions in yield with later plantings. The short growing season means late planting can have a more detrimental effect on yield: It limits the number of days providing light for growth and reproduction.

Yields in Indiana, Ohio and Kentucky tend to stay higher even when planting well into June. Keep in mind that areas prone to sudden death syndrome (SDS) may suffer more incidence of the disease with early planting.

Here are the most common constraints to early planting:

  • Soils are too cold.
  • Soils are too wet.
  • Planting conflicts with planting of other crops.
  • Harvest timing conflicts with other crops.
  • Diseases such as SDS threaten to hurt yields.
  • Grower mindsets are geared toward tradition planting dates.

    High Soybean Yields Require High Nutrient Levels

    Historically, growers haven’t paid as much attention to the nutrients needs of soybeans as they have of the needs for corn. Consequently, they’ve been establishing a ceiling on yields, failing to achieve the full potential of modern soybean genetics. However, growers are becoming more interested in learning more about management changes that will drive higher yields.

    Many soybean growers are finding their yields are reaching just slightly above the levels for which they’re providing fertilizer, notes Dan Poston, DuPont Pioneer agronomy research manager in the southern U.S.

    “Building and maintaining soil fertility is a game changer,” Poston says. “If soils have the texture to hold nutrients, growers who build up nutrient levels can achieve long-term benefits. They’ll often see substantial results 4 to 5 years down the road.”

    Lighter soils, which don’t hold nutrients as well, may need more-frequent “spoon feeding” of critical nutrients, Poston says.

    Nitrogen Needs

    The daily nitrogen demand for high-yield soybeans is huge, Poston says. During seed fill, it can take 11 pounds of N per acre per day to produce a 100-bushel-per-acre soybeans crop.

    “As we begin to think about consistently producing high-yield soybeans, we must ask if we need some supplemental nitrogen,” Poston says. “We also must think about how we can supply all necessary nutrients efficiently through the growing season.”

    Growers may need to reconsider their nutrient needs based on yield targets. For instance, a field producing 80 bushels per acre may take up 416 pounds of nitrogen (316 pounds of it removed from the soil), 76 pounds of phosphorus (64 pounds removed from the soil), 256 pounds of potassium (112 pounds from the soil), 32 pounds of magnesium and 26 pounds of sulfur. To supply that amount of nitrogen consistently, the environment must be ideal for nitrogen fixation or nitrogen will have to be supplemented. Yield response to supplemental nitrogen fertilization is inconsistent.

    “The largest responses to nitrogen fertilizer on soybeans that I have observed has occurred on lighter-textured soils with low organic matter” says Poston. Poston also notes that one must also be able to assess pod load and determine yield potential and that fields that have greater than 70 bu/A yield potential are most likely to respond to supplemental nitrogen fertilizer.

    “Preferably we want the plant to fix its own nitrogen and much research is still needed to determine the role that supplemental nitrogen might play in high yield soybean production” Poston says.

    Variable-Rate Fertility

    Variable-rate fertilization is helping growers improve overall yields.

    “The biggest impact of variable rates is in making fields more uniform,” Poston says. “We can help poorer areas yield better by placing nutrients more accurately, applying them where we need them most.”

    Growers can spread the fertility costs out over several years by applying nutrients based on crop removal. Grid or zone sampling helps target these applications cost effectively.

       High Yield Soybean Nutrient Update
    R Flannery, 101 Bu/A Soybeans

     Nutrient Uptake per Day
      Soybean Stage   Days   N   P2O5   K2O
      – – – – – – lb/a/day – – – – – –
    3rd trifoliate  40  0.75  0.25  0.68
    6th trifoliate 11 1.45 0.55 2.72
    Full Bloom 16 7.81 1.75 5.75
    Early pod 15 9.13 2.27 9.6
    Soft seed 21 11.43 2.76 2.43
    Maturity 16 -3.38 -1.25 -2.25

    The value of sulfur

    Growers generally haven’t been keeping up sulfur levels in their fields. With much less sulfur settling into fields from the environment, levels are decreasing. Sulfur frequently becomes a yield-limiting nutrient in high yield potential soybeans.

    “We focus a little more on sulfur in corn than in soybeans,” Poston says. “Only about half of growers are applying sulfur, and those who do usually apply less than 20 lbs. per acre.”

    Soil recommendations for sulfur often call for 18 to 20 lbs. of sulfur. However, an 80-bushel-per-acre soybean crop can require up to 30 lbs of sulfur. Needs may be greater in soils with lower organic matter. Issues are worse on low organic matter soils. One must fully appreciate the amount of nutrients required to grow high yield soybeans.

    In summary, Poston says, growers who want to raise yields need to apply nutrient levels that are required to produce those ultra-high yields.

Soybean Yields Depends on Sunlight

Too often growers overlook the effect of light on soybean yield. Researchers have demonstrated that soybean yield can be increased 144% to 252% when additional sunlight is provided by pushing back neighboring plants from the V5 growth stage through harvest.

Providing plants with this additional sunlight from the R3 stage through harvest also resulted in higher yields than in the control group, but not nearly to the degree receiving that additional light at the early growth stage.

Increased light earlier likely caused more photosynthate to build up in the plant, increasing the number of pods on the plant. Light clearly can have a major impact on soybean yields by influencing pod set.

Role of Day Length

Dan Poston, DuPont Pioneer agronomy research manager in the southern U.S., notes it’s important to understand day length differs at various latitudes. Twice during the year, day lengths are equal at all latitudes: the March and September equinoxes. Maximum day length occurs at the summer solstice, around June 20. Ideally, soybean production would take advantage of the long days around June 20 to drive reproductive growth. If longer days occur before the reproductive phase, the plant will add vegetative growth that doesn’t necessarily contribute to higher yields and can lead to increased likelihood of lodging.

Selecting the appropriate maturity group for the planting date helps the crop take greater advantage of days with longer photo periods to drive more pod set. Growers who ignore the interaction between planting date and soybean maturity group may not obtain optimal pod set. In the central and northern Corn Belt, growers can take advantage of this by planting a variety of a longer relative maturity (0.5 to 1.0) and target an earlier-than-average planting date.

Different geographies will need to determine the appropriate relationship between local planting dates and maturities to match flowering and reproduction to the longest days of the summer. Hitting this mid-to-late-June timeframe also can help plants set pods before the hottest and most stressful days of summer hit.

Poston adds, this topic needs further investigation, but interest is growing in discovering ways to determine optimal relationships between local planting dates and maturity group performance.

Pest Control: Critical to Boosting Soybean Yields

A variety of pests can take tiny bites out of your yields throughout the growing season. The results can be a gut-wrenching decrease in final yield totals even with excellent genetics and Mother Nature’s cooperation. Most successful soybean growers do an excellent job of controlling pests.

“Controlling pests has been making soybean growers a considerable amount of money in the past 10 to 15 years,” says Dan Poston, DuPont Pioneer agronomy research manager in the southern U.S.

Scouting is critical, Poston insists. “Serious growers scout once a week prior to bloom and twice a week afterward.”

Today, growers have access to a great tool to limit some early-season stresses. Seed treatments offer impressively consistent returns, Poston points out.

“Seed treatments are absolutely essential, especially for growers who are planting early,” he says. “Using a fungicide-insecticide combination can help thwart fungal disease and insects that attack plants when soils are cool and damp.”

Seed treatments work extremely well in northern geographies, but they also are consistently profitable in the mid-South and other locations. Seed treatments work especially well with early planting dates, which have shown to produce higher yields.


While not every grower is set up to irrigate, those who can obviously have an opportunity to supply water when soybeans need it most. When temperatures rise above 90 degrees, soybeans require about 0.25 inch of water per day from the R1 through R6 stages (first flower through seed development) – even higher (up to 0.4 inches per day) if pod fill occurs in extreme heat. Soybeans can use more than 2.1 inches per week during peak demand. Growers who irrigate can sometimes supply this needed water when dryland soybeans must do without.

Rotating Soybeans and Corn

Rotating with at least 1 year (optimally 2 or more years) of corn helps raise soybean yields. This helps break the disease cycle, softening the impact of damaging pests. Growers who plant 2 consecutive years of soybeans in a field likely are putting a ceiling on yields compared to those using a corn-soy or a corn-corn-soy rotation

Walk Your Fields and Scout

Hands-on management is vital. Growers who get into the field, scout and take a proactive approach can set up crops for stronger yields. Growers should increase scouting frequency when the crop begins to bloom. Poston suggests growers scout fields once a week until the bloom stage and twice a week afterward.

Grid or Zone Sampling

Knowing the soil’s needs and applying nutrients where they’ll do the most good can boost yields. Technology is available to apply nutrients more accurately and get more bang for your fertilizer buck.

Deep Soils

While soil depth doesn’t guarantee higher yields, better performance tends to occur in fields with deeper soils. However, good management will help growers stretch yields in fields that provide good growing environments.