Physical effects of direct drilling equipment on undisturbed soils

Abstract

Abstract A number of combinations of groove formation and seed covering techniques, aimed at improving the seedling emergence from grooves created by a triple disc coulter (with plain pre-disc), were tested in an initially dry soil under controlled climatic conditions. It appeared that smearing and compaction either did not occur or were not associated with a reduction in seedling emergence from the triple disc grooves. A loose soil cover over the seeds did not improve seedling emergence performance although a less permeable polythene cover improved performance markedly. When seeds were pressed into the groove base, seedling emergence also increased significantly. A hypothesis to explain the probable dependence of seedling emergence on the in-groove soil moisture vapour retained by the groove covering medium is suggested. This was termed “moisture vapour potential captivity”(MVPC).