Research from Iowa State University and the Iowa Soybean Association suggests relay cropping systems that combine cereal rye and soybeans could improve soil health, increase farm revenue and create new feedstock opportunities for the biofuels industry.
Relay cropping involves planting soybeans into a growing cereal rye crop in the spring, allowing farmers to harvest two cash crops from the same field during a single growing season. Fall-seeded cereal rye maintains living roots through the winter to reduce erosion and capture excess nutrients. After the rye is harvested in July, the soybeans continue developing through the remainder of the growing season.
Researchers said multiyear field trials show the system can deliver both economic and environmental benefits, although success depends on careful management.
Farmers participating in the research manage the rye and soybean crops as separate enterprises despite occupying the same acreage. One participant plants cereal rye at 70 pounds per acre in the fall, followed by soybeans planted as early as possible in the spring at a population of 140,000 plants per acre. The system also includes an application of about 40 pounds of nitrogen per acre.
Although soybean yields are often lower than in conventional production, the additional rye harvest can offset those losses by providing a second marketable crop. The farmer also reduces production costs by cleaning harvested rye seed for reuse as cover crop seed rather than purchasing new seed each year.
Research led by Iowa State University found several management practices that improve system performance. Longer maturity soybean varieties produced higher yields in three of four site-years, with soybean yield losses declining by about 0.8 bushel per acre for every one-point increase in relative maturity. Soybean populations of 120,000 seeds per acre consistently outperformed lower seeding rates, while row spacing of at least 30 inches helped reduce crop damage during rye harvest.
For cereal rye, early October planting produced higher grain yields than later planting dates. Researchers also found seeding rates of 25 to 50 pounds per acre were sufficient when rye was established early, helping control input costs.
Water availability remains the primary challenge because both crops rely on the same soil moisture early in the season. Dry conditions can reduce soybean yields, making timely rye harvest critical. Iowa Soybean Association data showed soybean yields declined with each day rye harvest was delayed beyond July 1. Researchers recommended using Draper combine heads to harvest rye while minimizing damage to the soybean crop.
For biofuel producers, wider adoption of relay cropping could gradually increase the availability of cereal rye as an additional feedstock while maintaining soybean production on the same acres. Greater rye production could support markets for renewable fuels and other biobased products if processing capacity and demand continue to develop. At the same time, the system's emphasis on improved soil health, nutrient retention and erosion reduction aligns with sustainability goals that are becoming increasingly important across the renewable fuels supply chain. However, researchers noted that successful implementation depends on favorable weather conditions and careful crop management, factors that will influence how broadly the system is adopted and how much additional feedstock it can ultimately provide.
Source: Iowa Farm Bureau, "Growing more from every acre"