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1998 STEEP III Progress ReportRESEARCH PROJECT TITLE: Development of conservation farming systems for protecting soil and water quality in downy brome infested dryland farming areas.
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. Cropping systems treatments:
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. Table 1. Influence of Crop Rotation on Downy Brome - Gilliland Site.
* TF – Tillage
fallow (harrow grain stubble in the fall and spray glyphosate in spring
as needed). Table 2. Influence of Crop Rotation on Downy Brome - Shaw Site.
* TF – Tillage
fallow (harrow grain stubble in the fall spray in spring as needed). Table 3. Influence of Crop Rotations on Crop Yields - Gilliland Site.
* TF – Tillage
fallow (harrow grain stubble in the fall and spray glyphosate in spring
as needed). Table 4. Influence of Crop Rotations on Crop Yields - Shaw Site.
* TF – Tillage
fallow (harrow grain stubble in the fall spray in spring as needed). 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). From this study, several questions have arisen related to the conversion to alternative crop rotation systems. Specifically, acceptable protocols for fertilization, tillage, and seedling establishment of winter wheat after canola, canola following winter wheat, or recropping of spring barley following winter are not available. Recommendations for these alternative cropping practices and will be partly developed from this study. 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. Estimated Net Returns per Acre of Rotation
INTERACTION 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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