Cereal rye is widely regarded as an excellent cover crop for Midwest cropping systems. It establishes well and produces substantial above- and below-ground biomass across diverse locations, planting timelines and environmental conditions.

In Indiana, cereal rye is often the primary cover crop option for many corn and soybean farmers due to the timing of fall cash crop harvests and prevailing environmental factors. Its robust growth and biomass production effectively support cover crop goals, such as reducing excess soil nitrate in the fall and spring, suppressing weeds, influencing soil moisture, minimizing soil erosion and contributing organic matter to the soil.

However, despite these benefits, managing cereal rye in the spring can be challenging, particularly for farmers planting corn. Yield reductions in corn following rye are commonly attributed to reduced nitrogen availability and nitrogen immobilization caused by the high carbon-to-nitrogen ratio of rye biomass.

SAME FIELD: Planted side-by-side with the sulfur-deficient corn plants, these corn plants showed no sulfur-deficiency symptoms. They did not follow a cover crop.

More than nitrogen

Emerging evidence suggests that other nutrients also may play a role in this yield-limiting dynamic. Sulfur management in cash crops such as corn and soybean has continually been thrust into the spotlight due to factors such as improved air quality and improved fertilizer purity. This has resulted in less sulfur available for these crops and widespread sulfur deficiencies observed each year.

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Cereal rye is known to immobilize nitrogen due to its high carbon-to-nitrogen ratio, and it also has been shown to immobilize sulfur due to its high carbon-to-sulfur ratio. Although previous research has explored management strategies to mitigate nitrogen immobilization and associated yield losses, such as using starter fertilizers and in-season nitrogen applications, limited attention has been given to the sulfur dynamics in corn following cereal rye.

In 2024, preliminary research trials were conducted in West Lafayette, Ind., to investigate the impact of sulfur applications on corn yield following cereal rye. The trials included replicated treatments of cereal rye and no cereal rye cover crops, each with and without sulfur applications.

Sulfur was applied as ammonium thiosulfate mixed with 28% urea ammonium nitrate at sidedress during V5 to deliver 15 pounds of sulfur per acre. Visual observations from the trial highlighted notable sulfur deficiencies in corn following cereal rye, while no such deficiencies were observed in corn without a preceding cover crop.

YIELD HIT: Research trials in West Lafayette, Ind., show corn takes yield hits when following a cereal rye cover crop. The table shows the corn yield response to a cereal rye cover crop and an in-season sulfur application. In the fall, cereal rye was drill-seeded at 45 pounds per acre and chemically terminated two weeks before corn planting in the spring.

What data says

Yield data from the trial further supported these findings. In the absence of cereal rye, a sulfur application provided no yield benefit. However, when following cereal rye, a sulfur application resulted in a yield increase of 15 bushels per acre.

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These preliminary results suggest that sulfur applications may play a critical role in mitigating sulfur deficiencies and improving corn yields following cereal rye cover crops. This research is ongoing and will be expanded to additional locations in 2025 to further validate these findings.