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Weed management during spring crop production in eastern Washington presents many challenges. Many spring crops are weak competitors with weeds. In May of 2010 and 2011, two spring crop trials were initiated near Pullman, WA, to compare the relative competitiveness of barley (Hordeum vulgare L.), wheat (Triticum aestivum L.), lentil (Lens culinaris Medik.), and pea (Pisum sativum L.) using cultivated oat (Avena sativa L.) as a surrogate for wild oat (Avena fatua L.) competition. The experiment was arranged as a split-block split-plot design with four replications. One set of main plots included three oat density treatments (0, 63, and 127 plants m–2), while a second set included each crop species. Crop species main plots were then split into subplots of two different seeding rates (recommended and doubled). Crop populations decreased as oat density increased and increased as crop seeding rate increased. As oat density increased, preharvest crop biomass decreased for all crops, while oat biomass and yield increased. Oat biomass and yield were greater in legume plots compared with cereal plots. Increasing oat density decreased yields for all crops, whereas doubling crop seeding rate increased yields for barley and wheat in 2010 and barley in 2011. Compared with legumes, cereals were taller, produced more biomass, and were more competitive with oat.

Large impoundments remove substantial amounts of sediment and nutrients from rivers and often limit production by downstream primary producers and secondary consumers. Nutrient levels and macroinvertebrate and fish abundance in the lower Kootenai River (7thorder, mean annual discharge = 454 m3/s) in Idaho and Montana declined dramatically after Libby Dam was built in 1972. A subsequent study implicated ultraoligotrophic conditions (total dissolved P [TDP] ≤ 2 µg/L TDP) as a principal causative agent and prompted an on-going experimental nutrient-addition program for the Kootenai River downstream from Libby Dam, with dosing at the Idaho–Montana border. Pre-treatment monitoring began in 2003 and liquid ammonium polyphosphate fertilizer (10-34-0) was added each year during the growing season from 2006 through 2010 with a target TDP concentration of 3 µg/L and TN∶TP near 20∶1. We studied benthic macroinvertebrate responses to the experimental addition and hypothesized moderate increases in invertebrate richness, abundance, and biomass with little change in assemblage structure. We used a before–after control–impact BACI design with macroinvertebrate samples collected pre- and post-treatment from July to early November 2003–2010 from fertilized and unfertilized reaches. After treatment, mean modified (Oligochaeta and Chironomidae subtaxa excluded) total abundance increased 72%, mean total abundance increased 69%, and mean biomass increased 48%. Abundance of Ephemeroptera, the principal insect order in the study area increased 66%. Filter-feeder abundance also increased, indicating increased suspended organic matter in addition to the attached forms consumed by other benthic macroinvertebrates. The first 5 y of experimental treatment resulted in increased food resources for resident native fishes with no major alteration of macroinvertebrate community structure or trophic pathways.

During the past century, the Kootenai River, Idaho (USA), has experienced cultural oligotrophication following extensive levee construction, channelization, wetland drainage, and impoundment. A multiyear, whole-river nutrient-addition experiment was undertaken to mitigate these effects. The river was dosed with liquid agricultural-grade ammonium polyphosphate fertilizer (10-34-0) from June through September 2006–2010 to achieve an in-river total dissolved P (TDP) concentration of 3.0 µg/L. A fine-scale monitoring program included 8 sites over a 20-km reach (2 upstream control sites, one injection site, and 5 downstream treatment sites). Nutrient addition did not significantly increase N and P concentrations in the water column, but it significantly increased chlorophyll accrual rates and densities of edible green algae and diatoms. Nutrient addition significantly reduced NO3 –+NO2 –concentrations, atomic TN∶TP ratios, and densities of inedible cyanophytes. Mean NO3 –+NO2 –values decreased along a downstream gradient below the nutrient-addition site, whereas chlorophyll accrual rate typically peaked immediately downstream from the nutrient addition site then decreased progressively downstream. Our study showed that nutrient addition is a useful river restoration technique for the Kootenai River.

Collaborative watershed group experiences reveal commonalities in their approaches to facilitate decentralized and inclusive watershed planning and management in the United States, and increasingly around the world. Although watershed groups are widely recognized in the United States for positive accomplishments across local, state, and regional scales, the role of government agencies as watershed group partners often remains ambiguous and inconsistent. This paper details results of a survey used to determine the status of Pacific Northwest (PNW) watershed group-agency partnerships relative to planning and management. Specific inquiry was directed toward: (1) the role of technical information flow; and (2) watershed group needs. Mail surveys were administered to 304 watershed group participants in Idaho, Oregon, and Washington. Sixty-nine percent of the surveys were completed and returned. Based on the collected survey data, PNW watershed groups rely heavily on agency officials for technical watershed information. Respondents perceive support of state government to be the highest relative to federal agencies, local governments, and university Extension offices. However, evidence from the survey suggests that partnerships are underutilized across all agencies and organizations concurrently vested in watershed planning and management in the PNW. Sustained operational funding, increased group participation, and baseline watershed data are the most pressing needs of PNW watershed groups and present a significant opportunity for expanding watershed group-agency partnerships.

Dose–response analysis is widely used in biological sciences and has application to a variety of risk assessment, bioassay, and calibration problems. In weed science, dose–response methodologies have typically relied on least squares estimation under the assumptions of normal, homoscedastic, and independent errors. Advances in computational abilities and available software, however, have given researchers more flexibility and choices for data analysis when these assumptions are not appropriate. This article will explore these techniques and demonstrate their use to provide researchers with an up-to-date set of tools necessary for analysis of dose–response problems. Demonstrations of the techniques are provided using a variety of data examples from weed science.

In the last 30 years several advanced technologies including guidance systems, auto‐steer systems, variable fertilizer rate systems, and section controllers have become mainstream in modern irrigated agriculture. Although these technologies have become widely accepted under irrigated conditions in the United States, their adoption under dryland conditions has lagged. The purpose of this study was to document the adoption of these technologies in the dryland inland areas of northern Idaho, eastern Washington, and northeastern Oregon. Three mail‐based surveys conducted 15 years apart in 1981, 1996, and 2011 were used to document adoption. All of the Dillman‐based surveys received grower responses in excess of 50%. In 2011, guidance systems, auto steer systems, section controllers, and variable rate application systems were used by 46.8, 36.6, 25.5, and 20.4% of the survey respondents, respectively. The use of these technologies was less than 2% in 1981 and less than 10% in 1996. The factors of annual precipitation zone, grower age, number of years farmed, and farm size all had an impact on the use of modern technology. In general, variable rate systems were more popular in the drier areas. Younger farmers were more likely to have adopted the new technologies, and new technology use was more widespread on the larger farms. Impact Statement This article is important because it contains a 30‐year history of how quickly modern technologies have been adopted in northern Idaho and eastern Washington. This article is unique because medium‐term production changes (20–40 years) are seldom documented by a single research/extension program in production agriculture.

Seed germination, one aspect of fitness, of chlorsulfuron-resistant (R) and -susceptible (S) kochia biotypes collected in North Dakota and Kansas was compared at 8, 18, and 28 C. Cumulative germination, characterized for each biotype using a Weibull function, was different at 8 and 18 C but not at 28 C. The Kansas R biotype reached 50% and maximum germination 70 and 300 h before Kansas S biotype at 8 C and 12 and 100 h before the S biotype at 18 C, respectively. The North Dakota R biotype reached 50% and maximum germination 12 and 100 h before the North Dakota S biotype at 8 C, respectively, and they were not different at 18 C. The resistance trait affects the cumulative germination process of kochia and may affect resistant-weed management strategies implemented early in the growing season when temperatures are lowest.

Farmers grow crops in the dryland region of the Pacific Northwest (PNW) using tillage practices ranging from moldboard plowing to no-tillage. The objective of this study was to determine the effect of tillage on persistence of imazamox herbicide in intermediate and high precipitation zones of the inland PNW. Along with a nontreated control, imazamox was applied to imidazolinone-tolerant winter wheat in the fall and spring at one, two, and three times the maximum labeled rate at locations near Genesee, ID, Davenport, WA, and Pendleton, OR. Moldboard plow, chisel plow, and no-till tillage treatments were implemented soon after wheat harvest and yellow mustard was planted the following season to determine crop response. Experiments were conducted at each location in 2005 to 2007 and 2006 to 2008. There were significant location by year and year and location interactions. There was no significant tillage by imazamox rate interaction, except at Pendleton in year 2, for all measured yellow mustard responses (crop injury, biomass, and yield). Genesee was colder than Pendleton and had more precipitation than Davenport, resulting in more injury to yellow mustard at Genesee than at Pendleton but less than at Davenport. Davenport had greater injury than the other two locations, likely due to lower soil pH, higher organic matter (OM), and cooler, drier climate, which allowed imazamox to persist longer in the soil. Overall, Pendleton had the least yellow mustard injury, which likely was related to its warmer, wetter climate and the concomitant rapid soil dissipation of imazamox. Tillage did not reduce the persistence of imazamox. Yellow mustard had the lowest injury and had greater mature biomass and seed yield in no-till seeded plots when averaged across imazamox rates compared to moldboard and chisel-plowed plots. Nomenclature: Imazamox; yellow mustard, Sinapis alba L. ‘IdaGold’, winter wheat, Triticum aestivum L.

Repeated use of sulfonylurea herbicides in continuous, no-till winter wheat selected for a herbicide resistant biotype of prickly lettuce in Idaho. Greenhouse experiments were conducted to compare the relative competitiveness and growth rate of sulfonylurea herbicide resistant (R) and susceptible (S) prickly lettuce. The S biotype of prickly lettuce produced 31% more aboveground biomass than the R biotype averaged over all densities. Both biotypes were equally competitive when analyzed for both inter- and intrabiotype competition. In relative growth rate studies, regression analysis showed that the S biotype accumulated biomass 52% faster than the R biotype. The results of this study showed that the S biotype was superior to the R biotype in biomass production and growth rate, but competitiveness appeared to be equal for both biotypes. Other fitness parameters must be measured before fitness differences between biotypes can be determined.