Paper Withdrawn
Monday, November 13, 2006 - 8:45 AM
52-5
Assessing Corn Yield Losses Using C-13 Discrimination.
John Pullis, D.E. Clay, S.A. Clay, and J.L. Kleinjan. South Dakota State Univ., Plant Science Dept. Ag Hall, Brookings, SD 57007
Methods are needed to assess yield-limiting factors in production fields. The Carbon-13 discrimination method, utilizing the abundance of the 13C isotope to assess plant health, is one such method that has shown promise in previous studies involving wheat and soybeans. The objective of this study was to develop an approach for quantifying the influences of weed, nitrogen, water and light stresses in corn. Weed (velvetleaf / no velvetleaf) and light treatments (0, 40, 60% shading) were assessed in 2004 and nitrogen (200 lb N/acre or 0 lb N/acre), water (irrigated / non-irrigated) and light treatments (0, 40, 60% shading) were assessed in 2005. In 2004, velvetleaf was used to simulate competitive stressors on corn and shading simulated light stress from competing plants. The presence of velvetleaf between the corn rows resulted in corn grain yield losses with corresponding increases in discrimination values. Similarly, increased shading intensity resulted in losses in corn grain yield with corresponding increases in discrimination each year. In 2005, the high N fertilizer level (200 lb N/acre) resulted in slight increases in yield and discrimination. Irrigated corn provided greater yield compared with non-irrigated corn. Increased shading intensity led to decreased corn grain yield and increased discrimination in this study. The strong effect that shading (light stress) has on overall corn grain yield shows the importance of sunlight for corn productivity.