Ridge‐Tillage Corn Response to Point‐Injected Nitrogen Fertilizer

Management practices to improve N‐use efficiency have been studied repeatedly for conventional tillage and no‐till systems. Little work has been done, though, to identify efficient N‐placement methods for ridge‐tillage systems. The objective of this study was to test the hypothesis that point injection of N in the ridge can optimize N‐use efficiency and corn ( Zea mays L.) production in ridge tillage, compared with broadcast N or injection between rows. Corn‐soybean [ Glycine max (L.) Merr.] rotation studies were conducted between 1986 and 1988 on Webster and Marna silty clay loams (fine‐loamy, mixed, mesic Typic Haplaquoll and fine, montmorillonitic, mesic Typic Haplaquoll, respectively). Treatments consisted of a control (no N) and factorial combinations of three N‐placement methods (broadcast, point injection between rows, or point injection in rows) and five rates (22, 45, 67, 112, and 157 kg N ha −1 ) applied as urea‐NH 4 NO 3 solution (UAN). Fertilizer‐N recovery by plants was determined at four growth stages in labeled‐N microplots. Corn yields, percentage of N derived from fertilizer, and percentage of fertilizer N recovered were significantly greater with injected N than with broadcast N. Injection position generally did not affect plant response. Point injection of N fertilizer can improve N‐uptake efficiency over broadcast methods in ridge‐tillage corn, but the importance of injection position was not substantiated.