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 measu re corn emergence rate and stand establishment while monitoring seedbed tem perature 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 wat er content in the top 0.10 m was measured a minimum of two times per week u sing time domain reflectometry (TDR) and estimated daily using a budget mod el. Measured and estimated soil water contents were similar (R-2 = 0.73) an d 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 plan ting date-site-years had stands below 80%, and they were characterized by s oil temperatures at or below 12.5 degrees C combined with high soil water c ontents (>90% available water). Rate of emergence was not associated with s tand establishment (P > 0.10) and could not be predicted from soil temperat ures below 12.5 degrees C. Results suggest that reduction in stand establis hment 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.