Wednesday, November 4, 2009: 1:45 PM
Convention Center, Room 319, Third Floor
Abstract:
Residual soil nitrogen (N) levels were considerably elevated in several key row crop production areas of Texas. A 7-year study investigating N management in cotton indicated that residual N levels ranged from 34 to over 181 kg/ha to a depth of 1.22 m. Only 23% of study sites showed a yield response to supplemental N fertilizer. Grain sorghum is commonly used as a rotational crop with cotton and though it has a different root structure than cotton, grain sorghum also may benefit from residual soil nitrogen. However, there is limited information about how to properly credit residual N from different soil depths. First-year field studies were initiated in the Blacklands and Coastal Bend regions of Texas to evaluate the response of grain sorghum to residual soil N. Supplemental N was applied to achieve soil test recommendations based on residual soil NO3-N at 0 to 15-, 0 to 30-, and 0 to 60-cm. Yields at most locations were limited by a relatively dry mid season. Reducing N fertilizer applications for grain sorghum based on residual soil NO3-N to 60 cm did not affect grain yield.