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1999 STEEP III Final ReportRESEARCH PROJECT TITLE: Development of conservation
farming systems for protecting soil and water quality in downy brome infested
dryland farming areas. INVESTIGATORS: Daniel A. Ball, Associate
Professor, Weed Science, OSU Columbia Basin Ag Research Center, Pendleton Cooperators: Dale Wilkins, Agricultural
Engineer, USDA-ARS CPCRC, Pendleton PROJECT OBJECTIVES:
KEY WORDS: Conservation tillage, Downy brome, Crop rotation, Canola STATEMENT OF PROBLEM: Downy brome is the most troublesome weed in dryland wheat/fallow cropping systems in the PNW. Historically, control measures have relied on inversion tillage and/or stubble burning to bury or destroy downy brome seed. Although these practices can keep downy brome at manageable levels, soil erosion, runoff, and evaporative water loss can be excessive where soil is not protected by residue. Non-traditional crop management practices including continuous, no-till spring cropping, rotations with canola, chemical fallow techniques, flex cropping, and/or improved residue management, must be developed to provide cropping systems which maintain profitability while protecting soil resources. ZONE OF INTEREST: Low rainfall, shallow soil, wheat/fallow regions of OR, WA, ID. Project specifically addresses alternative crop rotations, residue management, and weed management inputs in agronomic zones 4 and 5 (cool, dry soils, shallow or deep). ABSTRACT OF RESEARCH FINDINGS: Large scale, replicated plots were established in spring of 1993 on a commercial field near Pilot Rock, Oregon to compare several cropping and herbicide treatments for downy brome control, soil resource protection, and economic viability. A second site with the same treatments was established in the area in spring of 1994. Treatments were designed to optimize downy brome management and maintain adequate crop residues for erosion control. Comparisons between fallow management strategies utilizing secondary tillage (disc or sweeps), or chemical fallow indicates that secondary tillage increased winter emergence of downy brome and volunteer cereals which allowed for improved control of these weeds in the rotation. Inclusion of fall seeded canola in the rotation could increase or decrease densities of downy brome depending on timing of downy brome control in the canola crop. Conventional field preparation utilizing moldboard plowing reduced downy brome populations compared to chisel plow field preparation, but resulted in inadequate levels of crop residue necessary for erosion control. Downy brome infestations were higher in conservation tillage winter wheat-fallow rotations than in conventionally grown wheat-fallow or in conservation tillage systems incorporating barley, canola, or spring wheat. Yields between conventionally plowed and conservation tilled treatments were comparable, but inputs for conservation tillage wheat/fallow treatments were higher. RESULTS AND INTERPRETATION: Objectives 1 and 2: Large, replicated plots were established in spring 1993 on a commercial field near Pilot Rock, Oregon (Gilliland Site) to compare the effectiveness of several dryland wheat crop rotations for downy brome control, soil and water conservation, and economic viability. A second site with the same crop rotation treatments was established in spring 1994 (Shaw Site). A conventional plow-based wheat-fallow cropping system was compared to cropping systems designed to optimize downy brome management and maintain conservation compliance regulations. The experiment will conclude when all plots are planted to winter wheat (Gilliland in 1998, Shaw in 1999). Individual plots are approximately 0.5 acres in size with four replications and managed by growers and research station staff using field scale equipment.
Conservation tillage
treatments (1 through 5) employ spring chisel plowing as the primary tillage.
This is compared with the conventional, commercial practice of moldboard
plow primary tillage (treatment 6). At the Shaw site, a continuous no-till
hard red spring wheat was evaluated (treatment 7). Chemical fallow treatments
(2 and 4) consisted of a currently registered herbicide treatment (RoundupÒ,
LandmasterÒ, or Sure-FireÒ) applied after grain harvest
in the fall if necessary, and again in the spring before chiseling for
summer fallow preparation. Tillage fallow treatments (treatments 1 and
3) utilize a light sweep or disc tillage in the fall to maintain maximum
surface residue, but to "plant" downy brome seed, and if necessary,
a non-residual herbicide treatment (RoundupÒ) in the spring prior
to chiseling. Evaluations have
been made of total weed populations with emphasis on downy brome at both
sites in late January each year and again in late April. Surface residue
cover measurements were made using a line transect method each December.
Crop yields at both sites were estimated by harvesting the entire plot
area with commercial equipment. In the wheat-fallow
rotations, downy brome populations differed between plow (treatment 6)
and chisel (treatments 1 and 2), especially in the last year at the Gilliland
site where chiselled plots that did not receive fall stubble disking had
much greater levels of downy brome than moldboard plowed plots (Table
1). The three rotation of barley-fallow-wheat had lower levels of downy
brome compared to the wheat-fallow rotations that were chiseled (Table
1). Canola crops produced high levels of downy brome that infested subsequent
winter wheat crops if a selective grass control herbicide (PoastÒ,
Assure IIÒ) was not used in the canola (data not shown). Initial wheat yields
where chiseling was employed were lower than plots receiving conventional
moldboard plowing. However, after the second cycle of reduced tillage,
wheat yields were similar regardless of primary tillage method used (Tables
3 and 4). Canola yields were lower than expected due to heavy feeding
from local deer and elk populations, and dry conditions at time of seeding.
Problems with canola stand establishment, and insects also contributed
to lower than expected canola seed yields. Barley yields in the first
year, during establishment of the new crop rotation, were less than expected,
but improved as the rotation progressed (Tables 3 and 4). Percent residue cover
in newly seeded winter wheat was higher in wheat-fallow rotations utilizing
chisel compared to moldboard plowing (data not shown). Fall seeded canola
provided high amounts of green cover going into winter. Chemical fallow
during the fall resulted in greater levels of surface residue than did
fallow treatments receiving fall tillage. New production practices, fertilizer needs, tillage requirements, and pest management operations were required to establish and maintain these crop rotations, which emphasizes the need for more agronomic information before successful development of alternative crop rotation systems can occur. Specifically needed are acceptable protocols for fertilization, and tillage methods, and methods to establish winter wheat following canola, canola following winter wheat, or recropping of spring barley following winter wheat. Recommendations for these alternative cropping practices will be partly developed from this study.
Fall planting of canola is becoming a commonly accepted commercial practice in the Columbia Basin region of eastern Oregon. Canola planted after fallow in this study allowed downy brome populations to increase under the canola crop canopy. Postemergence grass herbicides could not be used if the canola crop canopy had closed before downy brome emergence. This resulted in an extremely heavy infestation of downy brome in subsequent winter wheat plantings (data not shown). Objective 2: The
second site established in spring of 1994 (Shaw Site) consists of a continuous
no-till spring cereal treatment in addition to treatments described in
the first objective. Downy brome and wild oat population dynamics, economic
inputs, crop production, and soil protection afforded by residue cover
and cropping practices are being evaluated as outlined for objective 1.
Downy brome density was very low in spring seeded wheat (Table 2). Wild
oat populations appear to be increasing, however (data not shown). Surface
residue cover has been adequate (data not shown). Objective 3: Field
tours have been conducted several times throughout the study period to
inform growers, extension agents, researchers, and soil conservation personnel
of project progress. Enterprise budgets were constructed for three of
the cropping systems utilizing conventional fallow. Net returns, revenue
less variable and fixed costs, were calculated for the rotations. Net
returns from individual enterprise budgets mean very little in the case
of a multiple year rotation. Each cropping operation is scheduled based
on the entire rotation not the production of a single crop. In a two year
rotation, such as wheat/fallow, wheat contributes one-half the costs and
revenues, while fallow contributes the other one-half . For the three
year rotations each part contributes one-third. Representative prices
and yields for the area producers were used in the initial estimation.
None of the three rotations had a positive net return.
INTERACTION (COOPERATION) WITH OTHER SCIENTISTS CONDUCTING RELATED ACTIVITY: All aspects of this study are being coordinated with D. J. Wysocki, Soil Scientist at the Columbia Basin Ag Research Center, OSU, and Mike Stoltz, Former Umatilla County Agent, and cooperating growers. Penny Diebel is conducting an economic analysis of alternative cropping systems. Richard Smiley is monitoring disease development. R. Adelman, NRCS, Pendleton is monitoring residue compliance. PUBLICATIONS AND PRESENTATIONS (current year): Diebel, P. L. and D. A. Ball. 1999. Economic Analysis of Conservation Farming Systems for Eastern Oregon Wheat Production. (in-press). A field tour at the Pilot Rock site was conducted on May 5, 1998 with approximately 20 growers participating. |
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