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United States Department of Agriculture

Agricultural Research Service

Research Project: Increasing Inland Pacific Northwest Wheat Production Profitability

Location: Soil and Water Conservation Research

Title: Tillage and no-tillage conservation effectiveness in the intermediate precipitation zone of the inland Pacific Northwest, United States

Authors
item WILLIAMS, JOHN
item WUEST, STEWART

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 14, 2010
Publication Date: July 1, 2011
Citation: Williams, J.D., Wuest, S.B. 2011. Tillage and no-tillage conservation effectiveness in the intermediate precipitation zone of the inland Pacific Northwest, United States. Journal of Soil and Water Conservation. 66(4):242-249.

Interpretive Summary: The predominant cropping system in the intermediate rainfall zone of the inland Pacific Northwest is the 2-year, winter wheat-fallow rotation, where there has been severe soil erosion in the recent past. Soil and water conservation in this region might be improved by increasing the complexity of the crop rotation and through conservation tillage practices. Traditional conservation tillage practices intended to retain substantial crop residue on the soil surface to guard against soil erosion and runoff also depend on multiple passes with tillage equipment, and thus disturbance of the soil surface, to prepare seed beds and control weeds. In this process, some residue is lost and soil structure is damaged. Although these systems are an improvement over traditional inversion tillage practices, water runoff and soil erosion continue to occur. No-tillage systems eliminate much of the soil disturbance associated with traditional conservation tillage practices by using a single pass of the seed drill for seed and fertilizer placement. The objective of this research was to evaluate the soil and water conservation responses of an intensified four year crop rotation under no-tillage and conservation-tillage management practices. We found ground cover and water infiltration rates significantly greater in the no-tillage treatment than in the conservation-tillage treatment. Consequently, the no-tillage treatment had lower runoff and soil erosion rates. The changes in infiltration, runoff, and soil erosion rates occurred more quickly and to a greater degree than we anticipated. Earlier studies of the benefits of no tillage in the inland Pacific Northwest have been ambiguous in their conclusions about the effectiveness of no tillage to significantly reduce runoff and soil erosion over traditional inversion-tillage (traditional) or conservation tillage where substantial residue remains on the soil surface. This research found that no tillage provided a significant improvement over conservation-tillage, which has been demonstrated superior to traditional tillage, at this location under mild weather conditions.

Technical Abstract: The predominant cropping system in the intermediate rainfall zone of the inland Pacific Northwest is the 2-year, winter wheat-fallow rotation typically practiced using multiple secondary tillage operations to control weeds and seed-zone soil moisture. This crop rotation has proven to be the lowest risk option for producers in areas that receive 305 to 430 mm of rainfall. Even using conservation tillage, these systems are prone to substantial soil erosion. Alternatives to this system include changing to no-tillage practices, increasing the cropping intensity, or a combination of both. The objective of this research was to evaluate the soil and water conservation responses of an intensified crop rotation under no-tillage and conservation-tillage management practices. We established a 4-year rotation consisting of winter wheat, spring peas, winter wheat, and fallow. No tillage consisted of seeding and fertilizing in one pass, two applications of herbicide, and harvest. Conservation tillage consisted of seed bed preparation using a chisel plow, two to three passes with secondary tillage (rodweeder), applications of herbicide, and harvest. The experimental design was a complete randomized block with four blocks, with two tillage treatment main plots per block and four subplots in each main plot for each phase of the 4-year rotation. We measured ground cover, tested infiltration using ring infiltrometers, and collected runoff and eroded soil from natural weather events in 1-m2 plots. Data were analyzed using mixed model ANOVA. Weather during the 4 years was relatively mild. Ground cover was significantly greater in the no-tillage treatment than in the conservation-tillage treatment. Infiltration rates were significantly greater in the no-tillage treatment than in the conservation-tillage treatment, a result confirmed by lower runoff and soil erosion values. Although greater surface residue levels were expected to occur with the initiation of the treatments, the changes in infiltration, runoff, and soil erosion rates occurred more quickly and to a greater degree than we anticipated. Earlier studies of the benefits of no tillage in the inland Pacific Northwest have been ambiguous in their conclusions about the effectiveness of no tillage to significantly reduce runoff and soil erosion over traditional inversion-tillage (traditional) or conservation tillage where substantial residue remains on the soil surface. This research found that no tillage provided a significant improvement over conservation-tillage, which has been demonstrated superior to traditional tillage, at this location under mild weather conditions.

Last Modified: 8/19/2014
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