Cob Removal Effect On Sediment and Runoff Nutrient Loss.

The cob fraction of corn (Zea mays L.) residue has been identified as a potential feedstock for ethanol production. However, the role of the cob in soil and water conservation is largely unknown. A rainfall simulator study was conducted in an irrigated corn field in Nebraska having replicated strips where corn residue was removed (6.0 ± 1.0 Mg ha^-1 residue remaining, 49.5% cover) or retained (12.9 ± 1.0 Mg ha^-1 residue remaining, 77% cover). Duplicate plots were installed in each strip and cobs were removed from one and retained in the other. Simulated rainfall was applied for 30 min. at a mean rate of 83 mm hr^-1 to plots at antecedent moisture and 24 hrs later at near saturated soil moisture conditions. Time to initiate runoff, runoff and sediment loss, and water quality parameters were measured. Residue removal reduced the time to initiate runoff (195.9 ± 1.0 vs. 239.5 ± 4.8 sec.) and increased sediment loss (0.36 ± 0.02 Mg ha^-1 vs. 0.27 ± 0.01 Mg ha^-1). Cob removal reduced time to initiate runoff during the antecedent run but not during the saturated run. Residue removal and rainfall treatment (antecedent vs. saturated) affected runoff water quality parameters (NO₃-N concentration, pH, soluble P concentration, and NO₃-N loss). Cob removal did not affect runoff, sediment loss, runoff pH, NO₃-N, NH₄-N, or soluble P loss. Cob removal when adequate stover was retained did not negatively affect erosion and runoff nutrient loss at this site.