Soil disturbance and draft force of selected seed openers

"Soil stepping" is a problem resulting from the accumulation of soil on top of seeds as the result of the excessive soil thrown by adjacent openers. The objective of this study was to characterise soil stepping associated with three different seed openers (hoe, winged hoe, and spoon) when operated at target depths of 25 and 50 mm in an indoor soil bin with a sandy loam soil (70 g kg(-1) sand, 16 g kg(-1) silt, and 14 g kg(-1) clay). Soil surface roughness, furrow cross-section, soil throw width, draft force, and vertical force were measured in a soil condition that had an average penetration resistance of 209 kPa, an average bulk density of 1184 kg m(-3), and an average soil moisture content of 25.8%. Soil disturbance characteristics and force requirements increased with the working depth of opener. Averaged for both working depths, the spoon opener created the largest furrow width (113 mm) and had the greatest soil throw (450 mm). For the controlled soil condition in which the evaluations were conducted, the critical spacing was 219, 255, and 285 mm for the hoe, winged hoe, and spoon opener, respectively. These results demonstrated that different openers caused different extents of soil stepping, and the hoe opener was least susceptible to soil stepping. Considering both soil stepping and draft force requirement, the hoe opener showed better performance than the winged hoe and spoon openers. (C) 2014 Elsevier B.V. All rights reserved.