TILLAGE EFFECTS ON CORN EMERGENCE RATES

Delayed emergence and reduced plant population are problems sometimes associated with corn production under conservation tillage. Poor emergence may be attributed to lower spring seed zone temperatures under the surface residue that accumulates with conservation tillage. In this study, conventional and conservation (chisel, ridge and no-till) tillage plots were established on sandy loam (orthic sombric brunisol) and clay loam (orthic humic gleysol) sites at Ottawa. Air temperature, seed zone (0.05 m), soil temperature, soil moisture and continuously-grown com emergence rates were monitored for 3 years. The time and thermal units required to achieve 50% emergence were deter mined for conventional and conservation tillage. An exponential function quantified the relationship between emergence and thermal units. Ridge and no-till treatments required an average of two more days to reach 50% emergence than conventional and chisel tillage treatments. Reduced soil temperatures in the no-till treatment accounted for much of the delay in emergence.