Rye cover crop and in-furrow fertilizer and fungicide impacts on corn optimum seeding rate and grain yield

Higher corn seeding rates and in-furrow fertilizer and fungicide combinations may be effective tools to overcome early-season corn (Zea mays L.) stress, stand reductions, and yield loss following a rye (Secale cereale L.) cover crop (RCC). The objective of this research trial was to evaluate corn growth and yield response and optimum seeding rate requirement following a RCC and different in-furrow starter treatments. Trials were established at three Kentucky, USA locations (2017–20), 7 site-years to evaluate corn response to seeding rate (49,421–108,726 seeds ha^-1) following a RCC and no cover crop, and in-furrow fertilizer (10-34-0) + fungicide (pyraclostrobin) and no in-furrow starter. At 2 of 3 locations, a RCC reduced corn V5 chlorophyll content and grain yield by 3.1% and 2.7%, respectively. The inclusion of an in-furrow starter failed to increase corn yield at any location and no interaction with a RCC was observed. Furthermore, an in-furrow starter reduced corn plant stand by 3.2% at 2 of 3 locations. At Lexington, quadratic regression analysis revealed that a higher corn agronomic optimum seeding rate (AOSR) and economic optimum seeding rate (EOSR) was required to maximize corn following a RCC compared to no cover crop. However, no significant stand loss was observed at this location. Overall, these results suggest that in-furrow fertilizer and fungicide do not ameliorate negative effects from a RCC and may cause negative impacts when applied simultaneously in-furrow. In addition, a higher corn AOSR and EOSR may be required following a RCC to maximize corn yield. However, because the effects of a RCC on AOSR were inconsistent among locations, further research may be required.