Rye performance in central Iowa under different seeding and nitrogen fertilizer rates

Abstract

The inclusion of a harvested winter cereal before soybean [Glycine max (L.) Merr.] can increase productivity and sustainability of a cereal-soybean rotation. Still, literature disagrees on proper seeding and fertilizer rates of the winter cereal for efficient production of both crops in the rotation. This study aimed to evaluate rye (Secale cereale L.) spring green ground cover, biomass production, and nitrogen (N) accumulation in a rye-soybean rotation, using three seeding rates (20, 40, and 60 kg ha⁻¹) and three N rates (0, 30, and 60 kg N ha⁻¹) from 2021 to 2023 in central Iowa. Remote sensing was used to assess rye growth. Green ground cover was up to 42% higher in the highest seeding rate (60 kg ha⁻¹). Conversely, rye biomass production was not affected by seeding or N rates and averaged 3.0 ± 1.1 and 4.9 ± 1.3 Mg ha⁻¹ in the first and second growing seasons, respectively. Rye N accumulation increased 0.13 and 0.51 kg N ha⁻¹ for each kg N applied in the first and second growing seasons, respectively. Soybean yield was similar among treatments but 19%–38% lower than the county average production, especially in the second growing season due to limited precipitation. This study provides new evidence that rye biomass production can be optimized with low inputs, whereas higher seeding rates increase spring green ground cover. However, because of reduced soybean yields, further studies are needed to evaluate rye harvest time and alternative soybean varieties to optimize soybean production after rye for central Iowa conditions.