Effects of drill coulter design and soil moisture status on emergence of wheat seedlings

Abstract

A field experiment is described where three contrasting direct drilling coulters (seed groove openers) were used for a total of twelve drillings at fortnightyly intervals. Wheat was drilled into an undisturbed silt loam soil in a temperate climate during a spring-summer-autumn period in the southern hemisphere. An experimental chisel coulter promoted significantly larger counts of seedling emergence than a triple disc coulter in two of the drillings, and was also superior to a hoe coulter in one of the drillings. In very dry conditions, where in 3 weeks no seedling emergence occurred with any of the coulters, sub-surface seedlings in the grooves made by the chisel coulter had survived in a further two of the drillings than was the case with the triple disc and hoe coulters. These results confirmed that the biological effect of the coulters was largely a function of the physical geometry of the grooves which determined their ability to retain and utilize the liquid and vapour moisture present in the seed micro-environment.