ABSTRACT:
Growers in low-precipitation (< 300 mm annual) dryland areas of the inland Pacific Northwest of the USA practice a wheat (Triticum aestivum L.) -fallow rotation where only one crop is grown every two years. When wheat yields are low, it is difficult to maintain adequate surface residue for erosion control during the ensuing fallow cycle. Russian thistle (Salsola iberica) is a major broadleaf weed in low-crop-production years, and it often produces more dry matter by grain harvest than the wheat crop it infests. In a 4-yr study, the effect of 3 tillage management treatments on retention of above-ground wheat residue and dead Russian thistle plants or “skeletons” during fallow was determined. Treatments were: 1) traditional (tillage), 2) minimum (herbicides and tillage), and 3) delayed minimum (herbicides and delayed tillage). Russian thistle infestation occurred 2 of the 4 yr when winter wheat failed and was replaced by spring wheat. Russian thistle skeletons were preserved as an important source of surface cover during fallow using minimum tillage, whereas they were wind-blown from the field or buried with traditional tillage. Minimum tillage also increased surface wheat residue compared to traditional tillage on all sampling dates. Results show the value of conserving Russian thistle skeletons for erosion control in low crop residue situations when this weed is likely to be present in large amounts.
Footnotes
William F. Schillinger is a research agronomist, Department of Crop and Soil Sciences, Washington State University, Lind, Wash. 99341 (schillw{at}wsu.edu); Robert I. Papendick is a soil scientist (retired), and Frank L. Young is a research agronomist, U.S. Department of Agriculture Agricultural Research Service, Pullman. Wash.: and Roger J. Veseth is an extension conservation tillage specialist, Washington State University and University of Idaho, Moscow, Idaho. They acknowledge the competent technical assistance of Harry Schafer, WSU agricultural research technician, and Bruce Sauer, farm manager of the WSU Dryland Research Station at Lind. Funding for this study was provided by the Solutions to Economic and Environmental Problems (STEEP II) Program and the Columbia Plateau Wind Erosion/Air Quality Project.
- Copyright 1999 by the Soil and Water Conservation Society
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