Assessing corn seedbed conditions for emergence

Seedbed temperature and moisture conditions affect crop emergence rate and stand establishment. A 4 x 4 factorial experiment arranged in a split plot design with four replications was conducted for 3 yr at four sites to measure corn emergence rate and stand establishment while monitoring seedbed temperature and soil water content in situ. Four planting dates, beginning as early as the soil could be worked and every 10 d thereafter, were the main plots and four corn (Zea mays L.) hybrids the subplots. Volumetric soil water content in the top 0.10 m was measured a minimum of two times per week using time domain reflectometry (TDR) and estimated daily using a budget model. Measured and estimated soil water contents were similar (R-2 = 0.73) and daily estimated values were used in the analysis. Stand establishment for most planting date-site-years ranged from 80 to 99%. Less than 15% of planting date-site-years had stands below 80%, and they were characterized by soil temperatures at or below 12.5 degrees C combined with high soil water contents (>90% available water). Rate of emergence was not associated with stand establishment (P > 0.10) and could not be predicted from soil temperatures below 12.5 degrees C. Results suggest that reduction in stand establishment under conditions of low (12.5 degrees C) soil temperature and high (>field capacity) soil water content may be a factor in corn yield reductions associated with reduced or no tillage.