Corn response to early- and late-vegetative nitrogen applications following a rye cover crop in Indiana

Rye (Secale cereale L.) cover crop (RCC) use offers environmental benefits but is often avoided prior to corn (Zea mays L.) due to yield losses and increased N fertilizer needs. This study evaluated corn response to N fertilizer timings following an RCC terminated prior to planting at three diverse locations in Indiana. Treatments included RCC and no RCC and N fertilizer applied at 44 kg N ha⁻¹ in a 5 cm to the side, 5 cm below the seed (5 × 5) starter at planting plus remaining N fertilizer applied at early vegetative (e.g., V4–V6), late vegetative (e.g., V9–V11), and early + late-vegetative growth stages. Total N fertilizer rates were constant across N application timings (201–235 kg N ha⁻¹ across locations) and a 0 kg N ha⁻¹ control was included. A significant (p < 0.1) RCC × N timing yield interaction was observed in 5 of 6 site-years, indicating optimum N timing differs with RCC presence. Without RCC, a 5 × 5 + late N application decreased yield in 4 of 6 site-years and a 5 × 5 + early + late N offered no yield benefit when compared to a 5 × 5 + early N application. With RCC, a 5 × 5 + late or 5 × 5 + early + late N decreased yield in 6 of 6 and 2 of 6 site-years, respectively, when compared to a 5 × 5 + early N application. Overall, late-vegetative growth stage N applications can cause corn yield reductions and should be avoided when following an RCC.