Winter Annual Weed Management and Nitrogen Rate Effects on Corn Yield
2013
Mueller, Nathan D. | Ruiz Diaz, Dorivar A. | Dille, J Anita | Shoup, Doug E. | Mengel, David B. | Murray, Leigh W.
Management of winter annual weeds (WAWs) can affect soil N availability and corn (Zea mays L.) production under no-till systems. The objective of this study was to evaluate the effect of delaying WAW herbicide applications on N availability and grain yield for no-till corn following soybean [Glycine max (L.) Merr.]. Field research was conducted in 2010 and 2011 at 14 sites with naturally-occurring populations of WAWs in eastern Kansas. A factorial arrangement of three herbicide application dates (November–March, April, and May) and five N rates (0, 17, 34, 67, and 135 kg N ha–¹) were used to evaluate the interaction between weed and N response. Corn plant population, soil nitrate-N, early corn N uptake, chlorophyll meter (CM) readings at silking, and grain yield were measured. Analysis across site-years, no significant interaction occurred between herbicide application date and N rate for variables measured. Delaying herbicide application until April significantly reduced early corn N uptake by 52 mg N plant–¹, CM readings at silking by 3.4%, and grain yield by 0.48 Mg ha–¹ across site-years. Using the N fertilizer equivalence values (based on CM readings and grain yield), an estimated additional 16 to 17 kg N ha–¹ was needed if herbicide application was delayed until April. Producers can increase corn N uptake and grain yield for rainfed no-till corn following soybeans in eastern Kansas by applying herbicides on WAWs before April.
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