Subsequent Winter Wheat Crop Research Articles

Rush skeletonweed (Chondrilla juncea) control and winter wheat injury with picloram applied in fallow

AbstractRush skeletonweed is an invasive weed in the winter wheat–fallow production regions of the inland Pacific Northwest. The objectives of this study were to determine the dose response of rush skeletonweed to picloram applied in the fall or spring of the fallow year with either a broadcast or weed-sensing sprayer, and to evaluate injury and grain yield in the subsequent winter wheat crop from these fallow treatments. Field studies were conducted between 2019 and 2022. Fall treatments were applied at one site in 2019, and one site in 2020. Spring treatments were applied at two sites in 2021. Four picloram herbicide rates (0, 140, 280, and 560 g ae ha−1), were applied with either a weed-sensing precision applicator or with a standard broadcast spray applicator. Rush skeletonweed densities in the wheat crop following fall-applied treatments declined with increasing picloram rates at both sites. Treatments applied with the weed-sensing sprayer achieved similar efficacy to broadcast treatments with an average of 37% and 26% of the broadcast rate applied. Spring-applied broadcast treatments resulted in reduced rush skeletonweed densities in wheat with increasing picloram rates. Picloram rate had no apparent effect on rush skeletonweed density when applied in the spring with a weed-sensing sprayer; however, the weed-sensing sprayer applied just 16% and 9% of the broadcast rate. Winter wheat grain yields were not reduced by fall picloram applications. Grain yields were not reduced by spring applications of picloram with the weed-sensing sprayer; however, grain yields were reduced by spring broadcast applications of picloram at both locations, and grain yields declined as the picloram rate increased. Applying picloram in the fall of the fallow phase with a weed-sensing sprayer provides effective and economical control of rush skeletonweed with a low risk for crop injury and yield loss in the following winter wheat crop.

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.

Choice of Summer Fallow Replacement Crops Impacts Subsequent Winter Wheat

Winter wheat (Triticum aestivum L.) is the foundation of dryland cropping systems in the Central Great Plains. The objective of this study was to quantify the effects of four short‐season spring‐planted crops used to replace summer fallow on the subsequent winter wheat crop. Wheat was seeded into four crop stubbles [spring triticale (×Triticosecale Wittmack), dry pea (Pisum sativum L.), foxtail millet (Setaria italica L. Beauv.), and proso millet (Panicum miliaceum L.)] at sites near Akron, CO, and Sidney, NE, in the fall of 2004 and 2005. These summer fallow replacement crops were planted into silt loam soils at three different soil water levels at planting (low, medium, and high). Winter wheat water use was 3.6 cm greater, and grain yield was 662 kg ha−1 greater in the high water treatment compared with the low water treatment averaged across all sites and years. Winter wheat used an average of 4.3 cm more water following early planted summer crops (triticale and dry pea) than after late planted summer crops (foxtail and proso millet), but this increased water use did not consistently translate into increased grain yield as a result of terminal drought at Sidney in 2006. The high water treatment always had a positive net return. The high cost of pea seed ($3.30 kg−1, USD) strongly reduced profitability. The flexible summer fallow cropping system appears to be most applicable when using short‐duration summer annual forage crops such as triticale and foxtail millet.

Effects of summer fallow management on take-all of winter wheat caused by Gaeumannomyces graminis var. tritici

Crop rotation is the oldest, and perhaps the best cultural practice for reducing the risk of take-all. The effects of crops sown before wheat in a rotation are known in detail, but we know little about the opportunities for reducing take-all risk by planting certain crops in the summer period between wheat harvest and the planting of a subsequent winter wheat crop. We investigated the effects on take-all of five summer fallow crops, two soil tillage treatments and a fungicide seed treatment, in a five site-year experiment. We tested the effects of oats, oilseed rape, mustard, ryegrass and volunteer wheat crops. Bare-soil plots were also included. Take-all epidemics varied with year and site. Summer fallow crops had a greater effect on tilled plots. The incidence and severity of take-all were significantly higher in the wheat volunteer plots, whereas maintaining bare soil provided the lowest level of disease. Oilseed rape had no significant effect on take-all incidence in our experiment. The best candidates for reducing take-all risk appeared to be oats, mustard and ryegrass. These summer fallow crops decreased disease levels only when associated with conventional tillage. Summer fallow crops did not alter take-all decline in the same way as a break crop after a wheat monoculture.

Eliminating Summer Fallow Reduces Winter Wheat Yields, but Not Necessarily System Profitability

Summer fallow is commonly used to stabilize winter wheat (Triticum aestivum L.) production in the Central Great Plains, but summer fallow results in soil degradation, limits farm productivity and profitability, and stores soil water inefficiently. The objectives of this study were to quantify the production and economic consequences of replacing summer fallow with spring‐planted crops on the subsequent winter wheat crop. A summer fallow treatment and five spring crop treatments [spring canola (Brassica napus L.), oat (Avena sativa L.) + pea (Pisum sativum L.) for forage, proso millet (Panicum miliaceum L.), dry bean (Phaseolus vulgaris L.), and corn (Zea mays L.)] were no‐till seeded into sunflower (Helianthus annuus L.) residue in a randomized complete block design with five replications during 1999, 2000, and 2001. Winter wheat was planted in the fall following the spring crops. Five N fertilizer treatments (0, 22, 45, 67, and 90 kg N ha−1) were randomly assigned to each previous spring crop treatment in a split‐plot treatment arrangement. The 3‐yr mean wheat grain yield after summer fallow was 29% greater than following oat + pea for forage and 86% greater than following corn. The 3‐yr mean annualized net return for the spring crop and subsequent winter wheat crop was $4.20, −$6.91, −$7.55, −$29.66, −$81.17, and −$94.88 ha−1 for oat + pea for forage, proso millet, summer fallow, dry bean, corn, and spring canola, respectively. Systems involving oat + pea for forage and proso millet are economically competitive with systems using summer fallow.

Predicting Winter Wheat (Triticum aestivum) Yield Loss Based on Jointed Goatgrass (Aegilops cylindrica) Populations From the Previous Season1

Abstract: To manage jointed goatgrass (Aegilops cylindrica), growers need an action threshold decision aid to assist them in deciding when to rotate to a spring crop instead of growing winter wheat (Triticum aestivum). A study was conducted in Washington from 1992 to 1995 to predict winter wheat yield loss based on a jointed goatgrass population in the previous year's winter wheat crop. To describe the relationship between jointed goatgrass density in year 1 and the resulting winter wheat yield loss in year 2, data were fitted to a rectangular hyperbolic model. First year jointed goatgrass densities in winter wheat of 1 to 5 plants/m2 led to a second year winter wheat yield loss of 3 to 30%. Yield loss was greater in a dry year than in a normal to wet year. To initiate an action threshold for jointed goatgrass successfully, growers need to incorporate data from this study with their knowledge of yield potential, price dockage of the subsequent winter wheat crop, and profitability of alternative spring cro...

Volunteer Barley (Hordeum vulgare) Control in Winter Wheat (Triticum aestivum) with MON 37500

Spring barley often is grown in rotation with winter wheat, and sometimes barley can overwinter in the subsequent winter wheat crop reducing grain yield and quality. Studies were established during 1996 and 1997 in winter wheat fields in southeastern Washington and near Moscow, ID, respectively, to evaluate control of ‘Steptoe’ volunteer barley with MON 37500, diclofop, and fenoxaprop/2,4-D/MCPA. Herbicides were applied to volunteer barley at two growth stages: two leaves to four tillers and more than four tillers with stems beginning to elongate. MON 37500 at 0.018, 0.026, and 0.035 kg ai/ha visibly controlled volunteer barley 83% or more at both application times. Diclofop at 1.12 kg ai/ha did not control volunteer barley, whereas fenoxaprop/2,4-D/MCPA at 0.66 kg ai/ha controlled volunteer barley 64 to 97% in 1996, but only 0 to 23% in 1997. In 1996 and 1997, volunteer barley density was reduced 80 to 99% in MON 37500-treated plots compared to the untreated control plots. Wheat grain grade was #1 for all MON 37500 treatments compared to grade #4 in 1996 and #3 in 1997 in the untreated plots. Grain price was reduced by dockage (barley kernels) for MON 37500-treated wheat $0 to $3.12/metric ton (MT), whereas price was reduced $23 to $26/MT for grain from untreated plots. In greenhouse studies, visible injury and height and biomass reduction varied among the 36 barley varieties treated with MON 37500.

Residual nitrogen effect of clover-ryegrass swards on yield and N uptake of a subsequent winter wheat crop as studied by use of 15N methodology and mathematical modelling

The residual effect of 2-year-old swards of clover-ryegrass mixture and ryegrass in monoculture on yield and N uptake in a subsequent winter wheat crop was investigated by use of the 15N dilution method and by mathematical modelling. The amount of N in the wheat crop, derived from clover-ryegrass residues was 25–43% greater than that derived from residues of ryegrass which had been growing in monoculture. Expressed in absolute values, the N uptake in the subsequent winter wheat crop was 23–28 kg N ha −1 greater after clover-ryegrass mixture than after ryegrass in monoculture. Up to about 54 kg N ha −1 of the N mineralised from the clover-ryegrass crop was calculated to be leached, whereas only 11 kg N ha −1 was leached following ryegrass in monoculture.

The effects of time of ploughing and time of drilling on the development and yield of the winter wheat crop following a clover ley

1. Two experiments designed to investigate the effects of different times of ploughing a clover ley on the growth and yield of the subsequent winter wheat crop are described and the results discussed.2. Although the different times of ploughing led to considerable differences in the growth of the wheat, their effect on yield was not consistent. This in agreement with the results of an earlier series of experiments. The effects of time of ploughing are attributed mainly to the resulting differences in the physical condition of the seed-beds.