Alex G. Ogg

Applying herbicides in irrigation water—a review

Abstract The technology of applying herbicides in irrigation water to control weeds selectively in crops has developed since the late 1960s. A review of the literature indicates that under the right conditions many herbicides applied through irrigation systems will control weeds selectively in crops. The greatest use of this technology has been with sprinkler irrigation systems, especially centre-pivots. Certain herbicides are also effective when applied through gravity flow irrigation systems, although uneven herbicide distribution and the potential for downstream contamination has limited the use of the technology in these systems. Although there is considerable interest in applying herbicides through trickle irrigation systems, problems associated with poor uniformity of herbicide application, rapid degradation of herbicides near the orifices, and potential health hazards to workers who might drink treated water, have prevented this technology from being adopted. Research is needed to determine how such factors as amount of water applied, soil texture, soil organic matter, soil moisture before and after herbicide application, water droplet size, timing of herbicide applications, herbicide concentration, herbicide properties, climatic factors, and the use of oils and other adjuvants affect the behaviour of herbicides applied through irrigation systems.

Integrated Weed Management Systems Identified for Jointed Goatgrass (Aegilops cylindrica) in the Pacific Northwest

Abstract Jointed goatgrass is an invasive winter annual grass weed that is a particular problem in the low to intermediate rainfall zones of the Pacific Northwest (PNW). For the most part, single-component research has been the focus of previous jointed goatgrass studies. In 1996, an integrated cropping systems study for the management of jointed goatgrass was initiated in Washington, Idaho, and Oregon in the traditional winter wheat (WW)–fallow (F) region of the PNW. The study evaluated eight integrated weed management (IWM) systems that included combinations of either a one-time stubble burn (B) or a no-burn (NB) treatment, a rotation of either WW–F–WW or spring wheat (SW)–F–WW, and either a standard (S) or an integrated (I) practice of planting winter wheat. This study is the first, to our knowledge, to evaluate and identify complete IWM systems for jointed goatgrass control in winter wheat. At the Idaho location, in a very low weed density, no IWM system was identified that consistently had the highest yield, reduced grain dockage, and reduced weed densities. However, successful IWM systems for jointed goatgrass management were identified as weed populations increased. At the Washington location, in a moderate population of jointed goatgrass, the best IWM system based on the above responses was the B:SW–F–WW:S system. At the Washington site, this system was better than the integrated planting system because the competitive winter wheat variety did not perform well in drought conditions during the second year of winter wheat. At the Oregon site, a location with a high weed density, the system B:SW–F–WW:I produced consistently higher grain yields, reduced grain dockage, and reduced jointed goatgrass densities. These integrated systems, if adopted by PNW growers in the wheat–fallow area, would increase farm profits by decreasing dockage, decreasing farm inputs, and reducing herbicide resistance in jointed goatgrass. Nomenclature: Jointed goatgrass, Aegilops cylindrica Host AEGCY; wheat, Triticum aestivum L. ‘Madsen’, ‘Stephens’, ‘Penawawa’, ‘Rod’, ‘Eltan’, ‘Alpowa’.

Postharvest Tillage Reduces Downy Brome (Bromus tectorum L.) Infestations in Winter Wheat

Abstract In the Pacific Northwest, downy brome continues to infest winter wheat, especially in low-rainfall areas where the winter wheat–summer fallow rotation is the dominant production system. In Washington, a study was conducted for 2 yr at two locations in the winter wheat–summer fallow region to determine the influence of four postharvest tillage treatments on vertical seed movement, seedbank depletion, and plant densities of downy brome. The four tillage implements included a disk, sweep plow, harrow, and skew treader. The study also included a no-till treatment for comparison. The sweep plow and disk led to the most vertical movement of downy brome seed compared with the no-till treatment. Approximately 75% of the fall postharvest seed in the no-till treatment was located either on the soil surface or in the 0- to 3-cm depth at both locations. In contrast, 75% of the seed in the disked treatment was located from 0 to 6 cm deep at both locations. The disk and sweep plow both decreased downy brome seed in the soil at the 0- to 3-cm depth compared with the harrow and no-till treatments. There was no difference in downy brome plant densities following postharvest tillage in the summer fallow due to any of the treatments. However, plant densities in the subsequent winter wheat crop were reduced by the disk and sweep plow compared with the no-till and skew-treader treatments. In general, seed densities as affected by the skew treader fell between the disk and the no-till treatments. The use of the sweep plow and the disk should be integrated into a weed management strategy for downy brome in the wheat–fallow region of the Pacific Northwest. Nomenclature: Downy brome; Bromus tectorum L.; winter wheat; Triticum aestivum L. Resumen En el Pacífico Noroeste, Bromus tectorum continúa infestando campos de trigo de invierno, especialmente en áreas con baja precipitación donde la rotación de trigo de invierno y barbecho de verano es el sistema dominante de producción. En Washington, se realizó un estudio por 2 años, en dos localidades en la región de rotación trigo de invierno y barbecho en verano, para determinar la influencia de cuatros tratamientos de labranza pos-cosecha sobre el movimiento vertical de la semilla, agotamiento del banco de semillas, y la densidad de plantas de B. tectorum. Los cuatro implementos de labranza fueron una rastra de discos, un cultivador de cuchilla, un cultivador de cincel, y un cultivador rotativo de dientes oblicuos. El estudio también incluyó un tratamiento de labranza cero para fines de comparación. El cultivador de cuchilla y la rastra de discos produjo el mayor movimiento vertical de semilla de B. tectorum al compararse con el tratamiento de labranza cero. Después de la cosecha en el otoño, aproximadamente 75% de la semilla en el tratamiento de labranza cero se localizó en la superficie del suelo o a una profundidad de 0 a 3 cm en ambas localidades. En cambio, 75% de la semilla en el tratamiento de rastra de discos se localizó de 0 a 6 cm de profundidad en ambas localidades. La rastra de discos y el cultivador de cuchillas disminuyeron la semilla de B. tectorum en el suelo de 0 a 3 cm de profundidad al compararse con los tratamientos de cultivador de cincel y la labranza cero. No hubo diferencia en la densidad de plantas de B. tectorum después de la labranza pos-cosecha en el barbecho de verano producto de los tratamientos. Sin embargo, la densidad de plantas en el siguiente cultivo de trigo de invierno se redujo con la rastra de discos y el cultivador de cuchillas al compararse con los tratamientos de labranza cero y el cultivador rotativo de dientes oblicuos. En general, la densidad de semillas producto del cultivador de dientes oblicuos estuvo entre los tratamientos de rastra de discos y la labranza cero. El uso del cultivador de cuchillas y la rastra de discos debería integrarse a estrategias de manejo de B. tectorum en la región de Pacífico Noroeste donde se tiene la rotación trigo-barbecho.

Developing National Research Teams: A Case Study with the Jointed Goatgrass Research Program1

Weed scientists are facing research problems, such as invasive weeds, that may require multidisciplinary approaches to solve. One example is jointed goatgrass, a winter annual grass invading winter wheat fields and not easily managed with conventional control tactics. A national research program was started in 1994 to develop jointed goatgrass management strategies. Involving more than 35 scientists with diverse scientific expertise, this national approach fostered cooperative research projects across 11 states. Research involved entomology, economics, plant breeding, plant physiology, genetics, and weed science, leading to successful management systems for jointed goatgrass. To help other scientists organize regional or national programs, we describe development and performance of the jointed goatgrass program as well as suggest ideas for possible improvement. Pivotal to the success of the program was a Steering Committee, whose role was to establish research priorities and coordinate research across the western United States. Nomenclature: Jointed goatgrass, Aegilops cylindrica Host. #3 AEGCY; winter wheat, Triticum aestivum L. Additional index words: AEGCY, Congressional special grant, integrated management, strategic planning, technology transfer. Abbreviations: BMP, best management practices; CSREES, Cooperative State Research, Education, and Extension Service; WSWS, Western Society of Weed Science.