Assessment of implement efficiency and soil structure under different conventional tillage implements and soil moisture contents in a silty loam soil

Abstract

Farmers' use of tillage implements under extremely dry soil conditions, ignoring optimum soil moisture conditions, results in low field efficiency, high fuel consumption and ultimately poor soil structure. Accordingly, the effect of tillage, applied under a range of near-plastic-limit soil moisture contents, on the efficiency of conventional tillage implements and subsequent soil structure, was investigated. Two conventional tillage systems: (i) moldboard plough followed by two cultivator passes and (ii) disk plough followed by two cultivator passes, were factorially combined with four soil moisture contents (θ) at tillage: dry soil, θ=5.0% w/w, and at 70, 80 and 90% of the moisture content at the soil's plastic limit (0.7θpl, 0.8θpl and 0.9θpl, respectively). The lowest field efficiency was observed under dry conditions, with a significant increase in efficiency at 0.7θpl, a further increase at 0.8θpl, and a subsequent decrease, compared to 0.7θpl and 0.8θpl, at 0.9θpl. Similarly, fuel consumption was greatest under dry conditions, decreasing at 0.7θpl and 0.8θpl, only to increase again at 0.9θpl. Overall, the lowest fuel consumption occurred at 0.8θpl. Under dry soil conditions the proportion of large aggregates (>8mm) was the lowest and that of small aggregates (<0.5mm) the greatest, whereas at 0.9θpl the converse was the case. At 0.7θpl and 0.8θpl, the proportions of large and small aggregates were low, while the proportion of desirable aggregates was greatest. At 0.8θpl the proportion of medium aggregates was greater than that at 0.7θpl. Therefore, in terms of post-tillage soil structure 0.8θpl was deemed the optimum θ for tillage of a silty loam soil. The aggregate stability of soil was higher under dry conditions and 0.7θpl, and lower at 0.8θpl and 0.9θpl under both moldboard and disk ploughing. A somewhat similar trend was observed under both conventional tillage implements; however, the disk plough followed by two cultivator passes offered a better performance in terms of field efficiency and soil properties than did the moldboard plough followed by two cultivator passes.