<p dir="ltr">Previous research has documented rye (Secale cereale L.) cover crop (RCC) benefits on weed suppression, erosion control, and water quality. However, RCC adoption is often low prior to corn (Zea mays L.) due to observed yield losses caused by a RCC. Therefore, further research is required to understand and develop corn agronomic, planting equipment, and N fertilizer timing recommendations following a RCC to minimize crop stress and yield losses. The objective of this research was to evaluate corn performance and yield in response to different N fertilizer application timings and after-market closing wheel types following a RCC using multiple field-scale environments. Treatments within the N timing study included three N fertilizer timings (2x2 starter + V5 sidedress, 2x2 + V10, and 2x2 + V5 + V10) and two RCC treatments (RCC and no RCC). Treatments within the closing wheel study included three closing wheel types: Standard Rubber (SR), Cruiser Extreme (CE), and Cupped Razor (MCR), and two RCC treatments (RCC and no RCC. Both studies were conducted at field-scale using commercial equipment at four locations in Indiana in 2022 and 2023. In the N timing study a significant (P<0.1) RCC x N timing interaction was observed in 5 of 6 site-years, indicating optimum N fertilizer timing differs with the presence of a RCC. Without the inclusion of a RCC, the use of a 5x5 + V10 or 5x5 + V5 + V10 N application decreased yield in 4 of 6 and 0 of 6 site-years, respectively when compared to a 5x5 + V5 N application. Whereas, with a RCC the use of a 5x5 + V10 or 5x5 + V5 + V10 N decreased yield in 6 of 6 and 2 of 6 site-years, respectively when compared to a 5x5 + V5 N application. In the closing wheel study, aftermarket closing wheels showed no difference in daily emergence timing and/or final plant stand in no-till conditions without a RCC. However, in RCC treatments, the CE improved total percent corn emergence [7 – 12 days after planting (DAP)] by 6 and 15% at 2 of 3 site-years. Whereas, the MCR improved percent corn emergence (7-12 DAP) by 8% in 1 of 3 site-years. Furthermore, corn grain yield was increased by 5-8 bu ac-1 at 2 of 3 site-years with CE when following a RCC and by 7 bu ac-1 at 1 of 3 site-years with MCR when following a RCC. Overall, results suggest farmers can combine the use of after-market closing wheels designed for high residue/RCC systems and optimum N fertilizer application timing (5x5 + V5 sidedress) to improve corn emergence, reduce N stress, and improve yield following a RCC.</p>

Nitrogen (N) is the most commonly over-applied nutrient in urban environments because of the large visual and growth increases. This over-application has led to an increase in the loss of N gas in the forms of ammonia and nitrous oxide, as well as an increase in nitrate leaching to surface and groundwater. Furthermore, excess N results in increased maintenance costs and landfill volume due to increased shoot growth from mowed clipping removal. Polymer coated urea (PCU) has proven to be an excellent source to these losses of N to the environment, but rate and timing parameters need study. A two-year field study, on sand and sandy loam soils in Provo, UT, was initiated in April 2014. Seven fertilized treatments included: urea split applied monthly; a single application of PCU (Agrium One Ap) applied in spring, a single PCU application in fall; two evenly split applications in spring and late summer; and three evenly split applications in spring, late summer, and late fall. These were compared to an untreated control. In addition the two application of PCU also had reduced rates of half and three-quarters, in addition to the full rate. Height and verdure measurements were taken on a weekly basis, along with periodic visual and biomass readings. All fertilized treatments resulted in a significant response to N as compared to the control. The single annual application treatments had significantly greater shoot growth during the weeks immediately after application and a significant reduction in verdure months later and, therefore, were unacceptable for consumer recommendation. Two applications of PCU, either at the three-quarter or full rates, were nearly identical in all measurements as compared to the spoon feeding of urea applied monthly. The half rate of two applications showed signs of inadequate N. Three applications of PCU was identical to two and, therefore, not recommended. This study shows two applications of PCU at the three-quarter rate is equally effective as spoon feeding the N. Doing so would result in less labor for fertilization. Further work is needed to evaluate other timing approaches for a single annual application, as well as long term effects of a reduced rate of N.