Nitrogen application methods and timing for corn after soybean in a ridge-tillage system

Nitrogen placement options for improved N efficiency are limited in ridge-tillage systems where primary and secondary tillage for fertilizer incorporation is absent, Studies were conducted for 3 yr on a Webster clay loam (fine-loamy, mixed, mesic Typic Haplaquoll) in southern Minnesota to determine the effect of placement and time of N application on corn (Zea mays L.) production and postharvest residual soil nitrate (RSN) and to evaluate the spoke- wheel injector for precise placement of urea-ammonium nitrate solution (UAN, 28-0-0) for corn after soybean [Glycine mar (L.) Merr,] in a ridge-tillage system, Nitrogen as UAN was either band-applied on the ridge, broadcast, or point injected into the ridge (PINJ-R) or valley (PINJ-V) and was compared with anhydrous ammonia (AA) injected into the valley (INJ-V), Single preplant and preemergence applications were compared with split applications where 30 to 40% was applied preemergence and 60 to 70% was applied at the V7 and V16 growth stages, Leaf N concentration at the R1 stage and whole plant dry matter and N concentration at the R2 stage were generally enhanced by single preemergence applications compared with split applications and by PINJ-R compared with the PINJ-V treatment. Grain yield, total N uptake, and net economic return were generally optimized by point injecting UAN and the injection of preplant AA compared with band and broadcast applications of UAN. Split applications did not produce higher yields, N uptake, or net economic return than single preemergence injected applications of N. However, RSN was highest with the V16 application of UAN under these nonirrigated conditions. Three-year average grain yield and net economic return were highest with the preemergence PINJ-R treatment, These results suggest that a single preemergence spoke-wheel application of UAN into the ridge or preplant AA in the valleys can be successfully used to optimize N management and corn production following soybean in a ridge-tillage system, Nitrogen efficiency will be enhanced and ammonia volatilization will be reduced with these application methods.