Relay cropping trials show hints of promise

   Can the practice of relay cropping when it involves soybeans – planting an overwintering cereal grain in the fall followed by beans in the spring – produce economic benefits while also helping a farm environmentally?

   On-farm research trials conducted by the Iowa Soybean Association (ISA) in conjunction with Iowa Learning Farms suggest that it is possible – with conditions.

   Alex Schaffer, senior research agronomist with the ISA, detailed the results of trials conducted on various Iowa farms in 2024, and shared those results during an ILF webinar Jan. 15.

   Reasons for interest in relay cropping, as outlined by Schaffer, included benefits to the farm (including) diversification, reduced herbicide use, profit potential) as well as to the environment (nitrate and carbon sequestration, improved water infiltration). In both cases, soil health and erosion prevention were listed as benefits.

   “Relay cropping is a chance to combine some economic gains with a conservation practice,” Schaffer said during the webinar.

   “The two are not mutually exclusive. Things that benefit the environment usually also benefit the farm when it comes to soil health and erosion prevention.”

   But there are caveats, not least of which is geography.

   The trials were assisted in part by a Conservation Innovation Grant (CIG) won by ILF.

   Those attempted in the northern part of the state, in Elma and Northwood – both near the Minnesota border – were considerably less successful than one farther south, in Oskaloosa.

   A trial in Le Mars in northwest Iowa using wheat instead of cereal rye proved to be one of the must successful.

   For a wider sample, Schaffer showed a slide detailing relay trial yield history from 2020 through 2024. While soybean yields in relay soybean fields in the north ranged from a low of 13 percent of the yields in sole soybean fields, up to 65 percent, those in the south Iowa fields ranged from 63 percent to 82 percent of sole soybean yields, and fields in central Iowa ranged from 71 percent of 86 percent over that time period.

   Other factors offered by Schaffer included these:

   • Requires specific management.

   • Carries elevated risk.

   • Variety selection is important.

   • Market expansion is crucial.

   As for the 2024 trials, the one in Elma was described by Schaffer as having “very poor relay soybean yields” and “marginal rye yields.”

   The best, in terms of rye, was in Oskaloosa, which had “good soybean yields” and “moderate rye yields.” The results there proved profitable when rye was sold as cover crop seed.

   “What they (the farmers) tell me is that they’re able to produce their own cover crop seed without taking acres out of corn and soybean production,” Schaffer noted.

   The wheat yield trial was in Le Mars, which had “good soybean yield” and “good wheat yield.”

   Using row indexing as a management practice, the farmer in Le Mars was able to “give the soybeans a lot more breathing room,” Schaffer said.

   “The beans in the relay don’t look a lot different than the beans in the sole crop strip,” he added. “There’s a lot of daylight making it down into those bean rows. And I think that really helps.”

   That trial showed soybean yields near 50 bushels per acre, and wheat yields close to 60.

   “I think that’s a really successful trial. We’re making a little bit of money here.”

   Schaffer said market expansion for small grains is crucial for the adoption of relay cropping as a common practice.

   “If there was a way to get some wheat into a pig ration, or some boxcars on train tracks across the state; there just needs to be some sort of a marketplace in the state of Iowa for the small grain if this is going to be a thing that takes off, Schaffer concluded.”