Seed placement effects on seedling establishment in direct-drilled fields

Two techniques for measuring seed placement distribution, a seedling tracing method and a soil core X-ray technique, were compared. Based on these methods, three determinant parameters were developed to define seed distribution; variation of depth, variation of lateral width and depth variation between rows.In the presence of a desirable in-groove micro-environment, both seed depth variations within and between rows had a negative relationship with seedling emergence percentage. Correlations between emergence and lateral width were low. Variations in seed depth were found to be associated with the mechanisms of seed ejection, and with the depth control method used on the openers.At two trial sites (in a sandy and silt loam soil) a simple winged chisel opener gave higher plant emergence than an experimental chisel S/2000 opener, a slot opener, a modified slot opener and a triple disc opener.