Winter Wheat Summer Fallow Rotation Research Articles

Downy brome (Bromus tectorum) management and herbicide resistance in dryland wheat production across northeastern Oregon

Abstract Downy brome (Bromus tectorum L.) is a difficult species to control in the dryland wheat (Triticum aestivum L.) production areas of northeastern Oregon. The selection of herbicide-resistant B. tectorum populations has further complicated B. tectorum management. A survey of wheat growers was conducted in 2021 and 2022 to understand B. tectorum management practices. The survey included four questions based on the growing seasons from 2017 to 2022 related to crop rotation, tillage versus no-tillage, irrigation versus dryland, and herbicide programs. To determine the extent of herbicide resistance, seeds were collected from 49 B. tectorum populations in wheat fields in northeastern Oregon and tested for resistance. Herbicides tested were clethodim, glyphosate, imazamox, mesosulfuron, metribuzin, propoxycarbazone, pyroxasulfone, pyroxsulam, quizalofop, and sulfosulfuron. Winter wheat–summer fallow rotation was the most predominant cropping system in the region. Most of the fields were in no-tillage systems, and none were irrigated. Pyroxasulfone applied preemergence and acetolactate synthase (ALS) inhibitors applied postemergence were the most often used herbicides for B. tectorum control in winter wheat. Glyphosate was the most frequently used herbicide for B. tectorum control in summer fallow. Resistance screenings confirmed that 46 of the 49 B. tectorum populations were resistant to ALS inhibitors with different cross-resistance patterns. Two populations were resistant to metribuzin and exhibited multiple resistance to ALS inhibitors. All populations were susceptible to clethodim, glyphosate, pyroxasulfone, and quizalofop. The widespread occurrence of ALS inhibitor–resistant B. tectorum populations limits effective postemergence herbicide options in winter wheat.

Macronutrients in Soil and Wheat as Affected by a Long-Term Tillage and Nitrogen Fertilization in Winter Wheat–Fallow Rotation

The insights gained from the long-term impacts of tillage and N fertilization on soil fertility are crucial for the development of sustainable cropping systems. The objectives of this study were to quantify the effects of 75 years of tillage and N fertilization on macronutrients in soil and wheat (Triticum aestivum L.) tissues grown in a winter wheat–summer fallow rotation. The experiment included three types of tillage (disc, DP; sweep, SW; and moldboard, MP) and five N application rates (0, 45, 90, 135, and 180 kg ha−1). Soil and tissue samples were analyzed for the concentration of total N, S, and C, Mehlich III extractable P, K, Mg, Ca in the soil, and the total concentration of the same nutrients in wheat tissue. Soil N concentration was significantly greater under DP (1.10 g kg−1) than under MP (1.03 g kg−1). The P concentration in upper 20 cm soil depth increased with increased N rates. Comparison of experiment plots to a nearby undisturbed pasture revealed a decline of P (32%), SOC (34%), Mg (77%), and Ca (86%) in the top 10 cm soil depth. The results suggest that DP with high N rates could reduce the macronutrient decline in soil and plant over time.

Wind erosion potential of a winter wheat–summer fallow rotation after land application of biosolids

Abstract Conservation tillage is a viable management strategy to control soil wind erosion, but other strategies such as land application of biosolids that enhance soil quality may also reduce wind erosion. No studies have determined the effects of biosolids on wind erosion. Wind erosion potential of a silt loam was assessed using a portable wind tunnel after applying synthetic and biosolids fertilizer to traditional (disk) and conservation (undercutter) tillage practices during the summer fallow phase of a winter wheat-summer fallow (WW-SF) rotation in 2015 and 2016 in east-central Washington. Soil loss ranged from 12 to 61% lower for undercutter than disk tillage, possibly due to retention of more biomass on the soil surface of the undercutter versus disk tillage treatment. In contrast, soil loss was similar to or lower for biosolids as compared with synthetic fertilizer treatment. Our results suggest that biosolids applications to agricultural lands will have minimal impact on wind erosion.

Feral Rye (Secale cereale) Control in Winter Canola in the Pacific Northwest

In the Pacific Northwest (PNW), feral rye is a predominant winter annual grass weed in the low-rainfall region where a winter wheat–summer fallow rotation has been practiced for more than 130 yr. Recently, producers began including winter canola in their rotation, which provides additional herbicide options to control feral rye. A 3-yr study was conducted in Washington to determine the efficacy of clethodim, quizalofop, and glyphosate on feral rye control and winter canola yield. During the first year of the study herbicides were applied in the spring, and they increased canola yield and decreased feral rye biomass, density, and seed production similarly when compared with the nontreated control. During the last 2 yr of the study, split applications of quizalofop and glyphosate were the most effective treatments for controlling rye (> 95%) and increasing canola yield. In general, clethodim was less effective than both quizalofop and glyphosate in controlling feral rye. Results from this study indicate that quizalofop in conventional or glyphosate-resistant winter canola and glyphosate in glyphosate-resistant winter canola can effectively control feral rye.

Implications of climate change on wind erosion of agricultural lands in the Columbia plateau

Climate change may impact soil health and productivity as a result of accelerated or decelerated rates of erosion. Previous studies suggest a greater risk of wind erosion on arid and semi-arid lands due to loss of biomass under a future warmer climate. There have been no studies conducted to assess the impact of climate change on wind erosion in the Columbia Plateau of the Pacific Northwest United States where wind erosion of agricultural lands can cause exceedance of national air quality standards. The Wind Erosion Prediction System (WEPS) was used to assess wind erosion and PM10 (particulate matter ≤10µm in aerodynamic diameter) emissions under a future climate projected by downscaling 18 Global Climate Models (GCM) for a conservative emissions pathway. Wind erosion simulations were conducted at Lacrosse and Lind, WA and Moro, OR on a winter wheat-summer fallow (WW-SF) rotation and at Lind on an additional winter wheat-camelina-summer fallow (WW-Cam-SF) rotation. Each rotation was subject to conservation or conventional tillage practices for a baseline (1970–1999) and mid-21st century climate (2035–2064). A significant increase in temperature and nominal increases in precipitation were projected by an ensemble of climate models for the Columbia Plateau by the mid-21st century. Soil and PM10 losses were 25–84% lower for a mid-21st century climate, due in part to greater biomass production associated with CO2 fertilization and warmer temperatures. The reduction in soil and PM10 loss is projected to be more apparent for conservation tillage practices in the future. Soil and PM10 losses were greater from a WW-Cam-SF rotation than WW-SF rotation when conservation tillage practices were employed during the fallow phase of the rotations. Despite accounting for differences in the length of each rotation, annual soil and PM10 losses remained higher for the WW-Cam-SF rotation than the WW-SF rotation. Soil and PM10 losses were more variable across years during 1970–1999 than 2035–2064; however, small and inconsistent differences in the coefficient of variation in soil loss between 1970–1999 and 2035–2064 suggest similarity in climate extremes which govern wind erosion.

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

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.

Influence of long-term tillage and crop rotations on soil hydraulic properties in the US Pacific Northwest

In the low precipitation zone (<0.3 m [11.8 in] annual precipitation) of the Inland Pacific Northwest, no-tillage continuous spring cereal and no-tillage spring cereal-chemical fallow rotations are being examined as alternatives to the traditional winter wheat–summer fallow rotation for soil conservation. There is limited information, however, regarding the long-term effects of no-tillage cropping systems on soil hydraulic properties in this semiarid region. The objective of this study was therefore to characterize infiltration, water retention, saturated hydraulic conductivity and bulk density of a silt loam that had been subject to various tillage and crop rotations in east-central Washington. Treatments examined included no-tillage spring barley–spring wheat (NTSB–SW), no-tillage spring wheat–chemical fallow (NTSW–ChF), and traditional winter wheat–summer fallow (WW–SF). Soil properties were measured in spring and late summer 2006 due to the vulnerability of the soil to rapidly dry and erode during these seasons. Saturated hydraulic conductivity was determined by the falling-head method, infiltration was measured using a double-ring infiltrometer, and water retention characteristics was assessed by examining the temporal variation of in situ soil water content. NTSB–SW resulted in higher infiltration and saturated hydraulic conductivity, lower bulk density, and larger and/or more continuous pores in the upper soil profile (<0.1 m [<3.9 in] depth) than WW–SF and NTSW–ChF. Infiltration and saturated hydraulic conductivity were lower for chemical fallow than for traditional fallow in spring whereas hydraulic conductivity was lower for summer fallow than chemical fallow in late summer. Soil hydrologic properties appeared more favorable for no-tillage continuous spring cereal rotations. These results are useful for soil and water management and conservation planning in the low precipitation zone of the Inland Pacific Northwest.

Soil properties governing soil erosion affected by cropping systems in the U.S. Pacific Northwest

In the low-precipitation zone (<300mm annual precipitation) of the inland US Pacific Northwest, no-tillage spring cereal rotations are being examined as alternatives to the traditional winter wheat–summer fallow rotation to control wind erosion. There is limited information, however, regarding the effects of no-tillage cropping systems on soil physical properties and surface characteristics that govern wind erosion in this semiarid region. The objective of this research was to characterize soil aggregates, wetness, strength, roughness, crusting, and crop residue cover and biomass of a silt loam that had been subject to various crop rotations for 11 years in east-central Washington. Crop rotations examined included no-tillage spring barley–spring wheat (NTSB/SW), no-tillage spring wheat–chemical fallow (NTSW/CF), and winter wheat–summer fallow (WW/SF). Soil physical properties were measured in spring 2006 after sowing wheat in the NTSB/SW rotation and in late summer 2006 after sowing winter wheat in the WW/SF and NTSW/CF rotations. In spring, the NTSB/SW and NTSW/CF rotations were characterized by a wetter soil as compared with the WW/SF rotation. In late summer, the NTSB/SW rotation was characterized by a soil surface with more standing stubble and greater crust cover and soil strength as compared with the WW/SF and NTSW/CF rotations. Our results suggest that spring-sown cereal and chemical fallow cropping systems result in wetter soils in spring and retain more surface residue in the late summer that will reduce the risk for wind erosion as compared with the traditional WW/SF rotation in the Pacific Northwest.

Friction velocity and aerodynamic roughness of conventional and undercutter tillage within the Columbia Plateau, USA

Friction velocity ( u * ) and aerodynamic roughness ( z o ) at the soil–plant–atmosphere interface affect wind erosion, but no attempts have been made to quantify these parameters as affected by tillage systems within the Columbia Plateau region of the Pacific Northwest United States. Wind velocity profiles above adjacent field plots (>2 ha), with plots subject to conventional or undercutter tillage during the summer fallow phase of a winter wheat–summer fallow rotation, were measured over 50 high wind events (wind velocities in excess of 6.4 m s −1 at a height of 3 m) during 2005 and 2006 near Lind, Washington to determine u * and z o of tillage treatments. Wheat stubble plots were subject to either conventional (disks) or undercutter (wide V-shaped blades) tillage in spring and then periodically rodweeded prior to sowing winter wheat in late summer. Prior to sowing, u * for conventional and undercutter tillage respectively averaged 0.36 and 0.46 m s −1 in 2005 and 0.38 and 0.40 m s −1 in 2006 while z o for conventional and undercutter tillage respectively averaged 2 and 7 mm in 2005 and 2 and 4 mm in 2006. The aerodynamically rougher surface of undercutter tillage was predicted to suppress vertical dust flux; this was collaborated with observations in the field where undercutter tillage reduced dust flux as compared with conventional disk tillage. Undercutter tillage, therefore, appears to be an effective management practice to roughen the surface and thereby suppress dust emissions from agricultural land subject to summer fallow within the Columbia Plateau.

Evaluation of the SWEEP model during high winds on the Columbia Plateau

AbstractA standalone version of the Wind Erosion Prediction System (WEPS) erosion submodel, the Single‐event Wind Erosion Evaluation Program (SWEEP), was released in 2007. A limited number of studies exist that have evaluated SWEEP in simulating soil loss subject to different tillage systems under high winds. The objective of this study was to test SWEEP under contrasting tillage systems employed during the summer fallow phase of a winter wheat–summer fallow rotation within eastern Washington. Soil and PM10 (particulate matter ≤10 µm in diameter) loss and soil and crop residue characteristics were measured in adjacent fields managed using conventional and undercutter tillage during summer fallow in 2005 and 2006. While differences in soil surface conditions resulted in measured differences in soil and PM10 loss between the tillage treatments, SWEEP failed to simulate any difference in soil or PM10 loss between conventional and undercutter tillage. In fact, the model simulated zero erosion for all high wind events observed over the two years. The reason for the lack of simulated erosion is complex owing to the number of parameters and interaction of these parameters on erosion processes. A possible reason might be overestimation of the threshold friction velocity in SWEEP since friction velocity must exceed the threshold to initiate erosion. Although many input parameters are involved in the estimation of threshold velocity, internal empirical coefficients and equations may affect the simulation. Calibration methods might be useful in adjusting the internal coefficients and empirical equations. Additionally, the lack of uncertainty analysis is an important gap in providing reliable output from this model. Published in 2009 by John Wiley &amp; Sons, Ltd.

Windblown dust influenced by conventional and undercutter tillage within the Columbia Plateau, USA

AbstractExceedance of the US Environmental Protection Agency national ambient air quality standard for PM10 (particulate matter ≤10 µm in aerodynamic diameter) within the Columbia Plateau region of the Pacific Northwest US is largely caused by wind erosion of agricultural lands managed in a winter wheat–summer fallow rotation. Land management practices, therefore, are sought that will reduce erosion and PM10 emissions during the summer fallow phase of the rotation. Horizontal soil flux and PM10 concentrations above adjacent field plots (&gt;2 ha), with plots subject to conventional or undercutter tillage during summer fallow, were measured using creep and saltation/suspension collectors and PM10 samplers installed at various heights above the soil surface. After wheat harvest in 2004 and 2005, the plots were either disked (conventional) or undercut with wide sweeps (undercutter) the following spring and then periodically rodweeded prior to sowing wheat in late summer. Soil erosion from the fallow plots was measured during six sampling periods over two years; erosion or PM10 loss was not observed during two periods due to the presence of a crust on the soil surface. For the remaining sampling periods, total surface soil loss from conventional and undercutter tillage ranged from 3 to 40 g m–2 and 1 to 27 g m–2 while PM10 loss from conventional and undercutter tillage ranged from 0·2 to 5·0 g m–2 and 0·1 to 3·3 g m–2, respectively. Undercutter tillage resulted in a 15% to 65% reduction in soil loss and 30% to 70% reduction in PM10 loss as compared with conventional tillage at our field sites. Therefore, based on our results at two sites over two years, undercutter tillage appears to be an effective management practice to reduce dust emissions from agricultural land subject to a winter wheat–summer fallow rotation within the Columbia Plateau. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Then and Now: 125 Years of Dryland Wheat Farming in the Inland Pacific Northwest

This article is a history of dryland wheat (Triticum aestivum L.) farming in the low‐precipitation (&lt;300 mm annual) region on the Columbia Plateau of the Inland Pacific Northwest (PNW) of the United States. Numerous technological advances, environmental problems, and sociological factors influenced wheat farming since its inception in 1880. The wheat‐based economy traces back to the pioneers who faced many challenges that included scarcity of water and wood, unprecedented wind erosion, drought, and minimal equipment. Throughout the years, major technological breakthroughs include: (i) horse (Equus caballus) farming to crude crawler tractors to the 350+ horse power tractors of today, (ii) transition from sacked grain to bulk grain handling, (iii) nitrogen fertilizer and herbicides, (iv) the rotary rodweeder, and (v) the deep furrow split‐packer drill to allow early planting of winter wheat into stored soil water. Cultural practices have evolved from repeated passes with high‐soil‐disturbance tillage implements to today's conservation tillage management. The 2‐yr winter wheat–summer fallow rotation continues as the dominant cropping system as it is less risky and more profitable than alternative systems tested so far. Improved wheat cultivars for deep furrow planting continue to be developed with good emergence, disease resistance, winter hardiness, grain quality, and other values. In the past 125 yr, average farm size has grown from 65 to 1400 ha and wheat grain yield increased from &lt;1.0 to 3.4 Mg ha−1. Since the 1930s, government farm programs have provided unwavering support that, in the last several decades, accounts for about 40% of gross farm income.

Validation of WEPS for soil and PM10 loss from agricultural fields within the Columbia Plateau of the United States

AbstractWind erosion from agricultural fields contributes to poor air quality within the Columbia Plateau of the United States. Erosion from fields managed in a conventional winter wheat–summer fallow rotation was monitored during the fallow period near Washtucna, WA, in 2003 and 2004. Loss of soil and PM10 (particulates ≤10 µm in diameter) was measured during six high wind events (sustained wind speed at 3 m height &gt;6·4 m s−1). Soil loss associated with suspension, saltation and creep as well as PM10 emission was used to validate the Wind Erosion Prediction System (WEPS) erosion submodel. Input parameters for WEPS simulations were measured before each high wind event. The erosion submodel produced no erosion for half of the observed events and over‐predicted total soil loss by 200–700 kg ha−1 for the remaining events. The model appears to over‐predict total soil loss as a result of overestimating creep, saltation and suspension. The model both over‐predicted and under‐predicted PM10 loss. High values for the index of agreement (d &gt; 0·5) suggest that the performance of the model is acceptable for the conditions of this study. While the performance of the model is acceptable, improvements can be made in modeling efficiency by better specifying the static threshold friction velocity or coefficients that govern emissions, abrasion and breakage of silt loams on the Columbia Plateau. Copyright © 2006 John Wiley &amp; Sons, Ltd.