Considering Double Crop Soybeans After Winter Wheat this Year?

considering double crop soybeans after winter wheat this year?

ERIC ANDERSON

MSU EXTENSION SOYBEAN EDUCATOR

DENNIS PENNINGTON

MSU EXTENSION WHEAT SPECIALIST

Winter wheat crop development is currently ahead of normal, opening a larger window for double-crop soybeans.

Table 1 shows current wheat growing degree day (GDD) accumulation through May 20, 2024. It also shows the 10-year average and departure from normal. Across these locations, wheat is about 9-11 days ahead of normal. If this weather pattern continues, wheat harvest could start a week or more earlier than normal this year.

coming one week later on average. The USDA’s Risk Management Agency expanded eligibility for federal crop insurance for double-crop soybean production following wheat in 58 counties in Michigan beginning in 2023 through a written agreement with no history of double-cropping (Fig. 1). Double-crop soybean yields range from 0 to 30 bushels per acre.

Two critical questions must be answered when considering double-crop soybeans: Is Table 1. Wheat GDD (base 0) accumulations since January 1, 2024 for there enough soil moisture left after wheat harvest? And is there enough time to raise selected Enviroweather stations. a soybean crop before a killing frost?

Station 2024 10 yr. Departure Departure Days Maintaining soil moisture through wheat avg.

(GDD) (%) grain fill via rainfall or irrigation is important not only to optimize wheat yield but also to Richville/Frankenmuth 826 616 209 34% 11 ensure enough moisture for germinating Pigeon 731 536 195 36% 10 soybean seed. Both surface and subsurface moisture levels are important. If there is Mount Pleasant (CMU) 770 575 195 34% 10 not enough moisture near the surface to Deerfield/Blissfield 936 756 180 24% 9 germinate the seed, critical time and yield potential will be lost. If the subsoil is dry, Cassopolis (GLBRC) 960 743 217 29% 11 the soybeans will be entirely dependent on rainfall for the remainder of the season resulting in a risky Planting double-crop soybeans in Michigan has venture. As the old adage goes for double-cropping, “If historically been a high-risk venture due to the limited June is dry, do not try.” growing season following winter wheat harvest. However, Assuming adequate moisture is available, addressing the climatic trend over the past several decades has the “enough time” question is multi-faceted and includes been a longer growing season with the first hard freeze management decisions in several areas.

Wheat Harvest Timing

Although wheat is typically harvested at 13–15% moisture for sale or storage, grain yield and quality will not be decreased when harvesting at 20-22% moisture. The obvious advantage is being able to plant 7–10 days earlier.

A study in Kentucky found harvesting wheat at 20–22% followed by immediate soybean planting resulted in an 8–12 bu/ac soybean yield increase compared with harvesting wheat at 13–15% moisture. Although glyphosate can be used as a pre-harvest aid in wheat, it is unlikely to significantly enhance wheat dry-down. The disadvantage of harvesting wheat early will be the added cost of drying or dockage.

Wheat Straw

Figure 1. Map of federal crop insurance eligibility for double-crop soybeans following wheat.

Adapted from USDA-RMA 2023.

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One approach to managing wheat residue is to cut wheat at 8–12” and ensure the combine distributes the chaff the entire width of the head. Growers can plant immediately following harvest with a no-till drill with discs that effectively cut through the residue down to planting depth. This has the added advantage of conserving existing soil moisture by avoiding tillage. If available, using a stripper

header will minimize residue on the ground. Taller wheat stubble will also help force soybeans to set pods higher off the ground, minimizing harvest losses due to missed pods.

Another approach is to cut and bale the straw prior to soybean planting. In addition to the extra revenue stream, the advantage here is in decreasing residue cover and increasing the chances of good seed-to-soil contact by avoiding “hair-pinning” of the straw in the furrow. The disadvantage is the delay in getting soybeans planted, but if this operation can begin the same day as wheat harvest, the planting delay may be minimal.

Soybean Planting

All of the same decisions that need to be made when planting soybeans in May need to be made when planting in July, with a few caveats. Conventional wisdom says plant

by July 10th for a profitable crop, although this is largely weather-dependent. A rough rule of thumb is that 1 bu/ac/ day is lost with delayed planting in July. With roughly 60 fewer days of the growing season ahead compared with a normal planting, changes must be made with respect to variety selection, seeding rate, row spacing and more.

• Select a medium to long maturity group (see Fig. 2) to maximize yield. Selecting an ultra-earlymaturing variety, although increasing the odds of reaching maturity before freezing, has consistently resulted in lower yields. However, a frost event prior to maturity will result in green plants at harvest. Ask your seed dealer about varieties that will yield well under double-crop.

• Stand count at harvest should be above 180K, so aim for a seeding rate of 200K–225K. • In order to quicken canopy closure and maximize sunlight capture, use a narrow row spacing, ideally 15 inches or less. This will also help with weed control during late-summer.

Weed Control

Choose fields for double-cropping where weeds were adequately controlled with spring herbicide applications in wheat. However, be aware that some wheat herbicides have rotational restrictions for soybean (e.g. Huskie - 4 months, Talinor - 10 months). Refer to Table 12 in the 2024 MSU Weed Control Guide for Field Crops for rotation restrictions for several common herbicides. Once wheat is harvested, weeds will typically grow rapidly as sunlight becomes more available. Depending on weed pressure and which species are present, these weeds may need to be controlled before soybean planting or emergence.

Volunteer wheat will also likely need to be controlled, so consider making a postemergence application after volunteer wheat has emerged and other weeds have outgrown injury from the wheat harvest. Remember, growing weeds (and volunteer wheat) will use up soil moisture, so timely control will be critical.

For those not planting a non-GMO soybean variety, selecting a herbicide-tolerant variety will provide more options for a double-crop weed control program. In-crop dicamba applications in Xtend soybeans are not allowed after June 30, so consider selecting Enlist E3, LibertyLink,

Figure 2. Soybean maturity zones in Michigan. or other traits besides Roundup Ready, particularly in fields with known glyphosate-resistant weeds. For example, 2,4-D choline, glyphosate and glufosinate can be safely used on Enlist E3 soybean with no calendar date restriction. Do not use herbicides that will injure soybean (e.g. Cobra, Flexstar, Blazer) as yield will be impacted in this shorter-season crop.

Also, consider including a residual herbicide to keep fields weed-free until canopy closure, particularly if later-emerging weeds like pigweeds or waterhemp are present.

Other considerations when considering double-crop soybeans following wheat: • Select fields with few stones or consider rolling fields after planting to reduce potential for cutter bar damage when harvesting shorter plants.

• Avoid planting double-crop soybeans in fields infested with soybean cyst nematodes (SCN) as the shortened time between soybean crops will increase SCN populations.

• Scout for soybean aphids. If aphid populations are high in earlier-planted soybeans, consider including an effective seed treatment (e.g. Gaucho, Cruiser) which would protect double-crop soybeans for 2-4 weeks as aphids move from earlier-planted fields to doublecrop fields. However, if aphids have reached threshold, a well-timed foliar application may provide more protection than a seed treatment. Aphids reproduce faster in late-planted soybeans and can cause more injury because the plants have less leaf area and root growth than soybeans planted earlier in the season.

Planting double-crop soybeans is risky in Michigan, but following the guidelines above can help reduce that risk.

Also, be aware that this practice will add another soybean crop to your rotation. This can decrease future soybean yields by promoting higher levels of soil-borne diseases and soybean cyst nematodes. michigan Soybean in-season management guide

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