Soil disturbance index as an indicator of seed drill efficiency in no-tillage agrosystems

In no-tillage agroecosystems, furrow openers prepare the seed line to place the seeds and fertilizers, and this event represents a unique opportunity to disturb the soil in this kind of crop system. Shanks are used to promote an appropriate soil physical condition, and, in case of soil compaction problems, shanks are used more frequently and at deeper layers of the soil profile. However, this deeper use causes greater draught and does not appropriately disturb the soil because narrow shanks have limited depth performance ("critical depth"). Here, we tested the operation of shanks in Oxisol and Alfisol. We assessed the shank performance 6-18 cm of depth, and we evaluated several soil disturbance parameters, such as area of groove, effective depth, and volume, as well as the demand of power force. Based on this evaluation, we calculated the specific power demand and the disturbance index, which is obtained from the ratio of disturbed area and maximum depth. With increasing depth of operation, the specific power demand increased in both soil types, while the disturbance index remaining approximately constant in the Oxisol and decreasing in the Alfisol. In the latter soil type, the shanks operated at more than 12 cm deep, and the lower disturbance index indicated a loss of efficiency in the soil disturbance. Therefore, the disturbance index is an efficient indicator of both the performance of seed drill shanks and the soil disturbance in no-till systems. (C) 2011 Elsevier B.V. All rights reserved.