Central and northern Ohio are near the limit where double-cropping is practical because of late harvesting of wheat and early autumn frosts. When double-cropping is not an option, relay intercropping is an option for harvesting two crops in a single growing season. In a relay intercropping system, soybean is planted into winter wheat between Feekes* 10.1–10.5 stages (wheat heading). Although no significant yield advantage occurs when planting soybeans into wheat at Feekes 9, it may be beneficial because more moisture is available to help soybeans establish. The goal of these planting dates is to have a well-established soybean plant (V2–V4 stage**) at wheat harvest.
*The Feekes Growth Scale contains numbers that represent new growth events. The Ohioline fact sheet, Wheat Growth Stages and Associated Management (AGF-126), provides additional information about wheat growth stages using the Feekes Growth Scale.
**V stages represent vegetative growth stages prior to the initiation of reproductive growth stages.
What is Wheat and Soybean Yield Potential in a Relay Intercrop System?
In a relay-intercrop system, winter wheat is often planted in 15-inch row widths to facilitate the intercropping of soybean. In this system, winter wheat yield is often reduced compared to monocrop wheat (wheat only) due to wider row widths and mechanical damage from intercropping soybean. Research in Wayne County, Crawford County, and Wood County, Ohio, show approximately 9%–12% yield reduction when wheat is grown in a relay-intercrop system compared to a monocrop system (Shrestha et al., 2021).
Soybean yield is also reduced in the relay-intercrop system compared to a monocrop system. In a three-year experiment in Wood County, Ohio, soybeans grown in a relay-intercrop system yielded 40% less compared to a monocrop system (Shrestha et al., 2021). For comparison, double-crop soybean yielded 66% less compared to a monocrop system. This shows that the relay-intercrop system is a viable alternative to double-crop soybean production in northern Ohio. The average soybean yield from 20 years of relay-intercrop soybean research in Crawford County is 33 bushels per acre, but this average includes two years where there was no measurable soybean yield. The first 15 years of relay-intercrop work in Crawford County included wheat grown in 10-inch rows with soybean interseeded. During the past five years, soybean and wheat were in a twin-row system, with two wheat rows spaced 8 inches apart followed by a 22-inch gap. Two rows of soybean (spaced 8 inches apart) were planted between the 22-inch gap. Overall, within a relay-intercrop system, soybean yield is reduced because of competition with wheat plants.
What is the Profitability Potential in a Relay Intercrop System?
Profitability of a relay-intercrop system can be extremely variable depending on input and commodity prices. To estimate the profitability of a relay-intercrop system compared to a monocrop wheat, monocrop soybean, and double-crop soybean following winter wheat, download The Ohio State University; College of Food, Agricultural, and Environmental Sciences; Excel-based partial return calculator (stepupsoy.osu.edu/wheat-production/wheat-profitability-calculator).
Based on a three-year study of various production systems in Wood County, Ohio, the most profitable system was wheat (with straw removed and sold) and double-crop soybean production (Table 1) (Lindsey et al., 2023). However, if wheat straw was not sold, the most profitable system was the soybean and wheat relay-intercrop system.
| Production System |
Gross Returna |
Costsb | Partial Return | Total P2O5 and K2O Valuec | Partial Return – Nutrient Removal |
| $/acre | $/acre | $/acre | $/acre | $/acre | |
| Wheat only (grown i7.5-inch row width) | 799 | 264 | 535 | 52 | 482 |
| Wheat only (7.5-inch row width) + straw sale | 1,065 | 277 | 787 | 93 | 694 |
| Soybean only | 880 | 199 | 680 | 77 | 603 |
| Wheat (15-inch row width) with soybean intercropped | 1,143 | 408 | 735 | 87 | 648 |
| Wheat (7.5-inch row width) with soybean double-cropped | 1,107 | 420 | 688 | 79 | 608 |
| Wheat (7.5-inch row width) with soybean double-cropped + straw sale | 1,373 | 433 | 940 | 120 | 820 |
| a Yield data used to calculate gross return were based on a 3-yr field study conducted in northwest Ohio (Shrestha et al., 2021). | |||||
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b Costs are based on Ohio Custom Rate Survey (Ward et al., 2022a) and Ohio Enterprise Budgets (Ward et al., 2022b, 2022c). |
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c Economic value of P2O5 and K2O is based on Ohio Enterprise Budgets (Ward et al., 2022b, 2022c) and removal rate based on values given in the Tri-State Fertilizer Recommendations for Corn, Soybean, Wheat, and Afalfa (Culman et al., 2020). |
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Management Considerations for Wheat and Soybean Grown in a Relay-Intercrop System
For the relay-intercropping system, soybeans are planted into standing wheat with a no-till planter or drill beginning in early May and can continue if damage to wheat can be minimized. Early June should be the latest relay-planting time because of a significant decrease in soybean yield potential after that period and an increased risk of wheat crop damage. The optimum time for relay- planting soybeans into the 10-to-15-inch space between wheat rows or twin-row wheat is at wheat heading (generally mid- to lateMay). While earlier planting in 10-inch rows is easier, the increased shading causes the soybean plants to have elongated internodes, causing weak soybeans and increased damage at wheat harvest. Earlier planting works best in wide-row wheat (15-inch row width), while the later plantings are best for narrow-row (10-inch row width) wheat. Growing wheat in 15-inch row widths facilitates the relay planting of soybeans. The spacing between wheat rows may vary as needed to accommodate implement wheels. When planting wheat, plugging various seeding units allows the placement of disk openers in a pattern to accommodate tractor and planter wheels. Both wheat and soybeans can be planted with the same equipment, or different planting tools may be used for the two crops. Any planting tool that creates good seed-to-soil contact is satisfactory, provided that 18–24 wheat seeds are planted per-foot-of-row and are evenly spaced. Row arrangement depends on available equipment and whether the grower emphasizes production of wheat or soybeans.
The use of early-maturing wheat varieties is not as important for relay-intercropping as it is for double- cropping, but harvesting wheat at high moisture (18%–20%) decreases the interference of soybeans during wheat harvesting. Early harvesting increases the test weight and wheat quality through higher grain moisture, but the wheat must be dried for storage. It is important to understand that the planting of somewhat vigorous wheat is required in this cropping system to suppress soybean growth until the wheat is mature. Otherwise, soybeans can grow too tall and are damaged during wheat harvesting. If soybeans grow too tall and wide row spacings are being used, shields may be added to the combine cutter bar to cover the sickle and push the beans down to prevent excessive cutting of the soybean plants’ tops while harvesting wheat. If the wheat stand and its vigor are poor in the spring, it is recommended to either refrain from intercropping soybeans or to wait until the wheat is headed before intercropping. In several research trials, the height of early-May intercropped soybeans was about two-thirds the height of wheat at harvest in early July and was affected during wheat harvest. The best intercropping results in Ohio to date have been with soybeans planted in mid to late May, when wheat heads are emerging. If relay-intercropping is done after this time, be aware that traffic associated with plantings tends to damage wheat and reduce its yield potential.
Improvements in machinery design, wider equipment, and modifications to confine traffic to the barren strips in skip-row wheat plantings can eliminate some crop damage. Shields to protect wheat from tires and planter units are useful equipment additions when wheat rows are spaced 10 to12 inches apart. Narrow rows should be carefully managed by adjusting wheel width and equipment to avoid damage to the wheat from soybean intercropping or to avoid damage to soybeans from wheat harvesting. In some cases, using narrow, dual, combine wheels will reduce damage to the soybean crop during wheat harvest. Damage to soybeans increases progressively with decreasing wheat-row spacing. During wheat harvests, straw should be chopped and evenly spread to avoid smothering the soybeans.
It is very important that wheat does not lodge prior to harvest. This allows it to be harvested without excessive damage to the soybeans. To prevent lodging, use stiff straw, lodging-resistant varieties, and limit nitrogen fertilizer applications. Ohio results have shown that the spring application of 75 pounds of nitrogen per acre in wheat (following soybeans) maximizes wheat yield without causing excessive lodging. Seeding rates for soybeans should be six to seven seeds per foot in 15-inch-wide rows,, and four to five seeds per foot in 10-inch-wide rows. The recommended seeding and nitrogen application rates for the wheat should not be exceeded to ensure that lodging of the wheat does not occur. Wheat lodging slows harvest, reduces grain quality, and increases the risk of damaging the soybean plants during wheat harvest.
In northern Ohio, full-season soybean varieties (relative maturity 3.5–3.8) performed best in this cropping system when planted at the end of May. Later-maturing varieties can be used in central Ohio. Early-June plantings require slightly earlier-maturing varieties than late-May plantings. Short-season varieties (relative maturity 2.8–3.1) flower too soon after planting and do not produce enough vegetative growth to provide a complete leaf canopy for maximum sunlight interception and therefore produce low yields.
Soil phosphorous and potassium levels should be greater than 30 ppm and 120 ppm (Mehlich-3), respectively. Up to 25 pounds of nitrogen per acre can be applied at wheat planting to promote autumn growth and tillering in timely planted winter wheat. Spring nitrogen applications should be made between green-up and the Feekes 6 growth stage.
References
Culman, S., Fulford, A., Camberato, J., Steinke, K., Lindsey, L., LaBarge, G., Watters, H., Lentz, E., Haden, R., Richer, E., Herman, B., Noekstra, N., Thomison, P., Minyo, R., Dorrance, A., Rutan, J., & Warncke, D. (2020). Tri-State fertilizer recommendations for corn, soybeans, wheat, and alfalfa (Ohio State University Bulletin No. 2567). Ohio State University.
agcrops.osu.edu/FertilityResources/tri-state_info
Lindsey, L. E., Richer, E., McGlinch, G. J., & Lindsey, A. J. (2023). Partial return calculator to compare monocrop, relay-intercrop, and double crop production systems. Crop, Forage & Turfgrass Management, 9(1), e20208.
doi:10.1002/cft2.20208
Shrestha, R. K., Richer, E., Clevenger, W. B., Davis, M., & Lindsey, L. E. (2021). Effect of mono-, relay-, and double-crop soybean systems on yield and profitability. Agronomy Journal, 113(2), 1747–1757.
doi:10.1002/agj2.20598
Ward, B., Barker, F. J., & Richer, E. (2022a). Ohio farm custom rates 2022. Ohio State University Extension.
farmoffice.osu.edu/sites/aglaw/files/site-library/farmmgtpdf/Ohio%20Farm%20Custom%20Rates%202022%20July17.pdf
Ward, B., Lindsey, L., & Loux, M. (2022b). Soybean production budget-2022. Farm office. Ohio State University Extension.
farmoffice.osu.edu/farm-management/enterprise-budgets
Ward, B., Lindsey, L., & Loux, M. (2022c). Wheat production budget (grain and straw)-2022. Farm office. Ohio State University Extension.
farmoffice.osu.edu/farm-management/enterprise-budgets
This fact sheet was orginally authored by Jason Hartschuh, Assistant Professor and Field Specialist, Dairy Management and Precision Livestock, Ohio State University Extension, on May 13, 2019.