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SWEEP Report #55

Soil Loss by Tillage Erosion: The Effects of Tillage
Implement, Slope Gradient, and Tillage Direction
on Soil Translocation by Tillage

Researchers: 
R.G. Kachanoski, M.H. Miller, and D.A. Lobb, Department of Land Resource Science, University of Guelph, Guelph, Ont.

Executive Summary

Evaluation Summary (Tech. Transfer Report Summaries)

View/Download Final Report  [1091 KB pdf] (appendices included)

Associated SWEEP/LSP Research

 

 

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Completed: June, 1992

Key Words:

tillage erosion, tillage implements, slope gradient, tillage direction, tillage depth, tillage ground speed, chisel plow, moldboard plow, disc, cultivator

Executive Summary

In the preceding study entitled "Management of Farm Field Variability. II. Soil Erosion Processes on Shoulder Slope Landscape Positions" net downslope soil translocation by tillage, tillage erosion, was identified as a major cause of the severe soil loss observed on upper slope landscape position in the complex topography of southwestern Ontario. This study examined the processes of soil translocation and tillage erosion in greater depth than the preceding study. The effect of tillage implement type on the magnitude of soil translocation and net downslope soil translocation by tillage under a range of slope gradients within a typical upland landscape was examined. The effects of other factors such as soil conditions, tillage depth, and tillage ground speed were also examined.

Soil translocation by four tillage implements, chisel plow, moldboard plow, tandem disc, and C-tine cultivator, was measured on a range of slope gradients in both upslope and downslope directions on two topographically complex, but similar, field sites in Huron County. The soil texture of both field sites was sandy loam. Soil translocation was measured using the tracer-pulse method. Chloride was utilized as the labelling element to generate the tracer-pulse. Soil translocation was calculated using the synthetic step response distribution synthesized from a succession of convoluted Cl pulse response distributions. Soil loss caused by tillage erosion was measured as the net downslope soil translocation by tillage. Paired plots were utilized to calculate net downslope soil translocation from upslope and downslope tillage operations.

Measurements of soil translocation, net downslope translocation and soil loss for all four tillage implements and for treatments of tillage implements were characterized as highly variable. The consequence of this variability was that soil loss and accumulation were observed throughout the topography, regardless of slope position. Although this variability existed, net soil losses were observed on the upper slope landscape positions for all four tillage implements, indicating that less soil is translocated upslope than downslope by each tillage implement. The chisel plow, moldboard plow, tandem disc and cultivator all caused tillage erosion which resulted in soil loss.

Measured soil losses resulting from two passes, one upslope and the second downslope, of the chisel plow, moldboard plow, tandem disc and cultivator, when averaged over the linear and convex upper slope landscape positions, were 0.19 kg/m2, 0.05 kg/m2, 0.43 kg/m2, and 0.54 kg/m2, respectively. Assuming each tillage operation is conducted upslope and downslope equally as often, the average soil losses per tillage pass for the chisel plow, moldboard plow, tandem disc and cultivator, were estimated to be 0.09 kg/m2 (0.9 t/ha), 0.03 kg/m2 (0.3 t/ha), 0.22 kg/m2 (2.2 t/ha), and 0.27 kg/m2 (2.7 t/ha), respectively.

Maximum measured soil losses between plots within the upper slope landscape positions resulting from two passes, one upslope and the other downslope, of the chisel plow, moldboard plow, tandem disc and cultivator were 2.96 kg/m2, 4.34 kg/m2, 1.14 kg/m2, and 2.97 kg/m2, respectively. Assuming each tillage operation is conducted upslope and downslope equally as often, the maximum soil losses per tillage pass for the chisel plow, moldboard plow, tandem disc and cultivator, were estimated to be 1.48 kg/m2 (14.8 t/ha), 2.17 kg/m2 (21.7 t/ha), 0.57 kg/m2 (5.7 t/ha), and 1.49 kg/m2 (14.9 t/ha), respectively.

The range between minimum and maximum values of soil translocation for each tillage implement provided indicators of potential net downslope soil translocation. The ranges for the chisel plow, moldboard plow, tandem disc and cultivator were 33.6 kg/m, 38.5 kg/m, 26.9 kg/m, 20.0 kg/m, respectively. The potential soil losses from the upper slope landscape positions, based on these ranges, for the chisel plow, moldboard plow, tandem disc and cultivator were estimated to be 0.51 kg/m2, 0.60 kg/m2, 0.55 kg/m2, 0.47 kg/m2, respectively. Assuming each tillage operation is conducted upslope and downslope equally as often, the potential soil losses per tillage pass for the chisel plow, moldboard plow, tandem disc and cultivator, were 0.26 kg/m2 (2.6 t/ha), 0.30 kg/m2 (3.0 t/ha), 0.28 kg/m2 (2.8 t/ha), and 0.29 kg/m2 (2.9 t/ha). Maximum absolute values of net downslope soil translocation for each tillage implement also provided indicators of potential soil loss. The maximum absolute values for the chisel plow, moldboard plow, tandem disc and cultivator were 30.4 kg/m, 17.8 kg/m, 26.9 kg/m, 14.6 kg/m, respectively.

All four tillage implements are considered erosive, however, the relative erosivity of the four implements could not be assessed conclusively because of the variability in the data. These observed values of soil loss are relatively small, but exceed acceptable limits. The rate of soil loss within complex topography is clearly scale dependent.

The results indicated that there are relationships between soil translocation and slope gradient, tillage depth and tillage ground speed; however, these relationships are not always strong nor are they consistent between tillage implements, or within tillage treatments of tillage implements. There was some indication that soil translocation increased as slope gradient, tillage ground speed, and tillage depth increased. There was also some indication that ground speed increased as slope gradient increased, that ground speed decreased as tillage depth increased, and that tillage depth increased as slope gradient increased.

The inconsistency in these relationships suggests that there are other factors involved in the translocation of soil by tillage other than slope gradient, tillage depth and tillage ground speed. The shape and arrangement of tillage tools, and the responsiveness of tillage operator, as well as slope gradient, tillage depth and tillage ground speed, may also affect soil translocation. In theory, the volume of soil translocated is determined by the tillage depth and the shape and arrangement of the tillage tools; the mass of soil translocated is determined by the soil bulk density; and the extent of the translocation is determined by the shape of the tillage tools, the ground speed of the tillage implement and the slope gradient. The tillage operator continuously adjusts both tillage depth and tillage ground speed, through the adjustment of gear ratio, to compensate for the effect of gravity on the mass of the tillage equipment as it moves through the landscape. The degree to which the operator has to adjust tillage depth and ground speed will depend on the tractor-implement match.

The implications of this study reaffirm the implications of the preceding study "Management of Farm Field Variability. II. Soil Erosion Processes on Shoulder Slope Landscape Positions" by Kachanoski et al. (1992b). In brief, those implications were:

  1. soil loss caused by tillage erosion is not restricted to shoulder slope landscape positions;

  2. predictive soil loss and crop productivity models that do not include the process of tillage erosion do not represent reality on cultivated agricultural land in complex topography; and

  3. preventative and corrective soil loss measures that do not include the reduction of tillage erosion will not be effective in controlling soil loss on upper slope landscape positions of cultivated agricultural land.

Implications arising directly from this study include:

  1. factors affecting tillage erosion include not only slope gradient and curvature, tillage depth, tillage ground speed and soil conditions, but also tillage tool shape and arrangement, tractor implement match and the response of the tillage operator to changing slope gradient; and

  2. studies which examine single tillage operations of specific tillage implements with limited replications have the potential to generate highly variable data due to the numerous factors involved, resulting in observations of soil loss and soil accumulation throughout the topography.

Recommendations to reduce tillage erosion induced soil losses on upper slope landscape positions in the upland regions of southwestern Ontario were outlined in the preceding study "Management of Farm Field Variability. I. Soil Erosion Processes on Shoulder Slope Landscape Positions" by Kachanoski et al. (1992b). In brief, those recommendations were:

  1. reduce tillage frequency;

  2. reduce tillage intensity;

  3. reduce the size of tillage implements; and

  4. vary tillage patterns within fields.

All four tillage implements were found to be erosive, but it could not be concluded which of the above recommendations would provide the greatest reductions in soil loss resulting from tillage erosion.

Recommendations for further research are:

  1. develop a practical and accurate method of measuring tillage depth for both primary and secondary tillage operations;

  2. conduct more rigorous studies of the effects of slope gradient and curvature, tillage depth, and tillage ground speed on soil translocation and tillage erosion;

  3. examine the role of tillage tool shape and arrangement, tillage operator, and tractor-implement match on soil translocation and tillage erosion;

  4. examine soil translocation and tillage erosion under a broad range of soil conditions to determine the effects of soil texture and soil moisture content on soil translocation.

 

Evaluation Summary

(From Technology Transfer Report Summaries - A. Hayes, L. Cruickshank, Co-Chairs)

The objective of this study was to determine the effect of tillage implement type on the magnitude of soil translocation and net downslope soil translocation by tillage under a range of slope gradients within a typical upland landscape. The effect of other factors such as soil conditions, tillage depth, and tillage ground speed were also examined. Two tillage treatments were conducted for each of four tillage implements - chisel plow, moldboard plow, tandem disc, and C-tine cultivator. Measurements were taken for both upslope and downslope tillage translocation over the range of slope gradients.

The results indicate that the chisel plow, moldboard plow, tandem disc, and cultivator all caused tillage erosion which resulted in soil loss. Less soil is translocated upslope than downslope by each tillage implement. There are relationships between slope gradient, tillage depth and tillage ground speed. However, these relationships are not always strong, nor are they consistent between tillage implements, or within tillage treatments of tillage implements. There was some indication that soil translocation increased as slope gradient, tillage ground speed, and tillage depth increased. There was also some indication that ground speed increased as slope gradient increased, that ground speed decreased as tillage depth increased, and that tillage depth increased as slope gradient increased. The inconsistency on these relationships may suggest that there are other factors involved in the translocation of soil by tillage other than slope gradient, tillage depth and tillage ground speed.

Implications arising from this study include:

  1. other factors involved in tillage erosion may include tillage tool shape and arrangement, tractor-implement matching and tillage operator responsiveness,

  2. the relationships observed between the many variables are specific to the tractor, tillage implement and operator.

Comments:

An excellent report that discusses some of the factors involved in tillage erosion but also raises questions about some other factors that may be involved.

Associated SWEEP/LSP Research:

  • SWEEP Report #38 - Management of Farm Field Variability. I. Quantification of Soil Loss in Complex Topography. II. Soil Erosion Processes on Shoulder Slope Landscape Positions

  • SWEEP Report #45 - Management of Farm Field Variability. III. Effect of Tillage Systems on Soil and Phosphorus Loss

  • SWEEP Report #46 - Management of Farm Field Variability. IV. Crop Yield, Tillage System, and Soil Landform Relationships

Future Research: ( ) indicates reviewers suggestion for priority, A - high, C - low.

        (A)

  1. Develop a practical and accurate method of measuring tillage depth for both primary and secondary tillage operations.

  2. Conduct more rigorous studies of the effects of slope gradient and curvature, tillage depth, tillage ground speed, and tillage implement on soil translocation.

  3. Examine the role of tillage tool shape and arrangement in the volume and extent of soil translocation.

  4. Examine the role of the tillage operator in the interaction between slope gradient, tillage depth and ground speed.

  5. Examine tillage erosion on a broad range of soil types to determine the effects of soil texture and soil moisture content on soil translocation.

 

 

 

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Created: 05-28-1996
Last Revised: Thursday, May 19, 2011 04:07:34 PM