|Marques Da Silva, Jose - UNIV OF EVORA, PORTUGAL|
|Soares, J - UNIV OF EOVRA, PORTUGAL|
Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 2, 2004
Publication Date: August 1, 2004
Citation: Marques Da Silva, J.R., Soares, J.M., Karlen, D.L. 2004. Implement and soil condition effects on tillage-induced erosion. Soil & Tillage Research. 78:207-216. Interpretive Summary: Excessive or improper tillage practices on sloping land can have a very detrimental effect on soil quality because of its potential effects on soil erosion. Three different soil erosion processes can be affected. These are water, wind, or tillage erosion depending primarily upon the location, climate, and displacement caused by the movement of soil particles down slope during the tillage operation. This study, conducted in Portugal, provides farmers and equipment manufacturers quantitative data to help them understand the process of tillage erosion with a moldboard plow and a disk harrow. Plowing up and down slope produced a net soil movement perpendicular to and in the direction of the tillage operation. For the moldboard plow used in this study, the net movement was approximately 0.45 m (18 inches), but this could be different for other tools. Tilling up and down slope with an offset harrow disk also produced a net soil transport in the direction of tillage. The amount of soil movement or tillage erosion was slope dependent and also varied with the soil condition (i.e., grassland stubble versus pre-tilled), the velocity of tillage, and how aggressively the disk was set (i.e., opening angle) for the tillage operation. This research demonstrated two relationships that soil quality specialists need to be aware of, the "annual tillage transport coefficient" and the "crop rotation tillage transport coefficient." These coefficients may be useful soil management indicators that will help land managers understand the long-term effects of crop production on soil quality.
Technical Abstract: Water, wind, or tillage-induced soil erosion can significantly degrade soil quality. Therefore, understanding soil displacement through tillage translocation is an important step toward developing tillage practices that do not degrade soil resources. Our primary objective was to determine the effects of soil condition (i.e. grassland stubble versus previously tilled soil), opening angle, and harrow speed on soil translocation. A second field study also conducted on a Lixisol but only in the stubble field, quantified displacement effects of moldboard plowing. Soil displacement or translocation after each tillage operation in both studies was measured using aluminium cubes with a side length of 15 mm as 'tracers'. Offset angles for the harrow disk were 20°, 44° and 59°; tractor velocities ranged from 1.9 to 7.0 km h-1 and tillage depth ranged from 4 to 11 cm. The depth of moldboard plowing was approximately 40 cm with a wheel speed of 3.7 km h-1. The translocation coefficients for the two implements were very different averaging 770 kg m-1 for the moldboard plow and ranging from 9 to 333 kg m-1 for the harrow disk. This shows that the moldboard plow was more erosive than the harrow disk in these studies. All three variables (soil condition, opening angle, and tillage velocity) were critical factors affecting the translocation coefficient for the harrow disk. Displacement distances were the largest for compacted soils (stubble field), with higher opening or offset angles, and at higher velocities. The results also showed significant correlation for (a) mean soil displacement in the direction of tillage and the slope gradient, and (b) soil transport coefficient and the opening angle. Our results can be used to predict the transport coefficient (a potential soil quality indicator for tillage erosion) for the harrow disk, provided tillage depth, opening angle, and tool operating speed are known.