Mulching is the most important of the three conservation agriculture principles in increasing crop yield in the short term, under sub humid tropical conditions in Zimbabwe

•Mulching and rotation effects were tested on both reduced and mouldboard tillage.•CA effects on crop yield followed the order mulch > reduced tillage > rotation.•Mulching increased maize and soybean grain yield by 14–42 %.•Fertiliser significantly interacted with mulching increasing crop yield under CA.•Individual CA principles were less effective in increasing yield than when combined.