Shawn P. Conley

Crop Management Practices in Indiana Soybean Production Systems

To meet the current and future needs of todays soybean producer it is vital that agricultural researchers and Extension specialists clearly understand the production concerns of our clientele. The objective of this research was to characterize the current management practices of Indiana soybean (Glycine max (L.) Merr.) growers, to identify specific educational needs, and to provide a framework for directing applied soybean research efforts. This assessment was conducted through a direct-mail survey. The results of this survey define distinct similarities and differences among growers of different farm operation size. Large acreage growers(;::: 1000 acres) were more likely to plant soybeans in rows spaced ll to 20 inches, reduce seeding rates, plant earlier, and have higher yields. Large acreage growers were also more likely to own a yield monitor, conduct on-farm research, use a computer, and routinely use the Internet. Our research also identified different research and educational needs based on farm operation size. By specifically targeting these needs, agricultural researchers and Extension specialists may improve the economic and environmental sustainability of each clientele group. Introduction Since the introduction of glyphosate tolerant soybean in 1996, management of soybean production systems have dramatically changed (lO). Today growers are faced daily with new crop and pest management technologies, new agronomic traits, and an ever changing pest complex. These new pests--the soybean aphid (Aphis glycines) (8) and the soybean rust fungus (Phakopsora pachyrhizi) (9 , ll)--may combine to form a potentially devastating pest complex, both of which require management with pesticides. To maintain commercial viability, soybean growers in the U.S. must continue to adopt new pest and crop management tools and technologies (12). The objective of this research project was to identify current agronomic production practices and concerns of Indiana soybean producers, to aid Purdue Extension and research faculty in developing Extension programs and educational materials that meet current and future clientele needs, and to provide a framework for directing applied soybean research efforts. Methodology and Statistical Analysis A seven-page direct mail survey was sent to 5000 Indiana soybean growers in August of 2005. Purdue University consulted with the Indiana Agricultural Statistics Service to develop and distribute the survey to growers representing various size farming operations and geographic regions within Indiana. Indiana Agricultural Statistics Service generated the mailing list, 1

Predicting soybean yield loss in giant foxtail (Setaria faberi) and common lambsquarters (Chenopodium album) communities

Abstract Widespread use of crop yield loss models based on weed density has been limited on account of spatial and temporal variability. Furthermore, research characterizing crop yield loss associated with two or more weed species is lacking for many cropping systems. Therefore, research was conducted to characterize giant foxtail and common lambsquarters leaf area, height, and shoot volume in soybean, to quantify the relative competitive ability of giant foxtail and common lambsquarters in a mixed–weed species environment, and to assess weed density, weed relative leaf area, and weed relative volume as predictors of soybean yield loss. Based on weed density, coefficient estimates of percent soybean yield loss as giant foxtail or common lambsquarters densities approached zero differed between years. In contrast, coefficient estimates of maximum soybean yield loss were similar between years. Based on weed relative leaf area, estimates of giant foxtail or common lambsquarters damage coefficients differed between years. Similarly, estimates of maximum soybean yield loss associated with common lambsquarters leaf area differed between years, whereas estimates of maximum soybean yield loss associated with giant foxtail leaf area did not change over time within a growing season or between years. Based on weed relative volume, estimates of giant foxtail or common lambsquarters damage coefficients differed between years. Similarly, estimates of maximum soybean yield loss associated with common lambsquarters volume differed between years, whereas estimates of maximum soybean yield loss associated with giant foxtail volume did not change over time within a growing season or between years. Based on weed density, weed relative leaf area, or weed relative volume, giant foxtail was more competitive than common lambsquarters in terms of soybean yield loss. Temporal variability of weed density, weed relative leaf area, and weed relative volume indicates that additional parameters may be required to accurately predict weed–crop interactions in a multiple–weed species community. Nomenclature: Giant foxtail, Setaria faberi Herrm. SETFA; common lambsquarters, Chenopodium album L. CHEAL; soybean, Glycine max (L.) Merr. ‘Asgrow AG2101’.

Estimating giant foxtail cohort productivity in soybean based on weed density, leaf area, or volume

Abstract Understanding weed–crop interactions is critical in predicting crop yield loss, but it is also important to understand how these interactions affect weed productivity. Therefore, research was conducted to characterize the weed relative leaf area and weed relative volume of several giant foxtail cohorts in soybean, and to assess weed density and cohort emergence time, weed relative leaf area, and weed relative volume as predictors of giant foxtail shoot biomass and fecundity. Giant foxtail cohorts emerged at VE (emergence), VC (cotyledon), V1 (first node), and V3 (third node) soybean growth stages and were thinned to densities of 0, 4, 16, 36, and 64 plants m−2. Based on weed density and cohort emergence time, the maximum shoot biomass per square meter or the maximum fecundity per square meter differed between years. In contrast, shoot biomass or fecundity per plant, as weed density approached zero, and the rate at which shoot biomass or fecundity decreased exponentially, as time increased, were similar between years. Based on the weed relative leaf area, the cohort effect on giant foxtail shoot biomass differed between years, whereas the cohort effect on giant foxtail fecundity was similar between years. Maximum giant foxtail shoot biomass per square meter or fecundity per square meter differed between years when estimated from weed relative leaf area. Based on the weed relative volume, the cohort effect on giant foxtail shoot biomass per square meter or fecundity per square meter was similar between years, as was the maximum giant foxtail shoot biomass per square meter or fecundity per square meter. The temporal stability of weed relative volume, used to describe giant foxtail shoot biomass or fecundity, may aid in improving bioeconomic weed management models. Nomenclature: Giant foxtail, Setaria faberi Herrm. SETFA; soybean, Glycine max (L.) Merr. ‘Asgrow AG2101’.

Effect of Location, Cultivar, and Diseases on Grain Yield of Soft Red Winter Wheat in Wisconsin

Knowledge is limited about the impact of foliar diseases on wheat yield in Wisconsin. The objective of this study was to compare yield and diseases of wheat cultivars in several locations in Wisconsin in 2009 and 2010. Thirty-six wheat cultivars were planted in a randomized complete block design at field sites near Arlington, Chilton, and Lancaster, WI. At a fourth location, Janesville, WI, the design was a split plot with foliar fungicide application at Zadoks growth stage (GS) 45 at the whole-plot level and cultivar at the subplot level. Disease assessments were made four times during the growing season for powdery mildew (PM), Septoria/Stagonospora leaf blotch (SLB), and leaf rust. Incidence and severity of Fusarium head blight were assessed on 100 heads per plot at GS 85. Linear mixed-model analyses were used to study the effects of location, cultivar, and disease on grain yield (α = 0.05). Overall, SLB and PM were the most prevalent diseases. SLB severity was uniform among locations and PM was most prevalent at Arlington and Chilton. In both years, yield was affected by location, cultivar, location-cultivar interaction, and location-SLB and location-PM interactions. Yield was also negatively affected by PM in 2010. No effect of fungicide on disease severity or yield was observed at Janesville in either year. These results suggest that cultivar selection and location strongly influence grain yield in Wisconsin and that powdery mildew is capable of reducing grain yield.

Does Weed Size Matter? An Indiana Grower Perspective about Weed Control Timing

Corn and soybean growers across Indiana were surveyed to assess their perceptions about the importance of preplant and POST weed control timing, focusing mainly on soybean production. Despite studies demonstrating the importance of planting into a clean field, almost a third of Indiana growers do not think it is important to plant into a weed-free seedbed and 74% do not use residual herbicides in glyphosate-resistant soybean production systems. Growers who farmed less than 200 ha were more likely to overestimate the ability of soybean to tolerate weed interference than growers who farmed more hectares. Growers who manage smaller farms were also more likely to use a one-pass weed control program than larger growers. This suggests that yield losses to weed interference may be greater for smaller farms than for larger farms. Weed size and density were the most common criteria used by growers to decide when to apply herbicides. This suggests that field scouting plays an important role in the decision-making process of growers. However, a substantial proportion of growers apply POST herbicides to large common lambsquarters and giant ragweed in an attempt to minimize the number of trips across the field for weed control. Delayed control of these species likely contributes to reduced crop yields, higher application rates, and to the survival of treated plants. Opportunities to improve control and increase yields through more optimal herbicide use appear possible for Indiana corn and soybean growers. Nomenclature: Glyphosate; corn, Zea mays L; soybean, Glycine max (L.) Merr.

Management of Pigweed (Amaranthus spp.) in Glufosinate-Resistant Soybean in the Midwest and Mid-South

Pigweeds are among the most abundant and troublesome weed species across Midwest and mid-South soybean production systems because of their prolific growth characteristics and ability to rapidly evolve resistance to several herbicide sites of action. This has renewed interest in diversifying weed management strategies by implementing integrated weed management (IWM) programs to efficiently manage weeds, increase soybean light interception, and increase grain yield. Field studies were conducted across 16 site-years to determine the effectiveness of soybean row width, seeding rate, and herbicide strategy as components of IWM in glufosinate-resistant soybean. Sites were grouped according to optimum adaptation zones for soybean maturity groups (MGs). Across all MG regions, pigweed density and height at the POST herbicide timing, and end-of-season pigweed density, height, and fecundity were reduced in IWM programs using a PRE followed by (fb) POST herbicide strategy. Furthermore, a PRE fb POST herbicide strategy treatment increased soybean cumulative intercepted photosynthetically active radiation (CIPAR) and subsequently, soybean grain yield across all MG regions. Soybean row width and seeding rate manipulation effects were highly variable. Narrow row width (≤ 38 cm) and a high seeding rate (470,000 seeds ha−1) reduced end-of-season height and fecundity variably across MG regions compared with wide row width (≥ 76 cm) and moderate to low (322,000 to 173,000 seeds ha−1) seeding rates. However, narrow row widths and high seeding rates did not reduce pigweed density at the POST herbicide application timing or at soybean harvest. Across all MG regions, soybean CIPAR increased as soybean row width decreased and seeding rate increased; however, row width and seeding rate had variable effects on soybean yield. Furthermore, soybean CIPAR was not associated with end-of-season pigweed growth and fecundity. A PRE fb POST herbicide strategy was a necessary component for an IWM program as it simultaneously managed pigweeds, increased soybean CIPAR, and increased grain yield. Nomenclature: Glufosinate; pigweed, Amaranthus spp.; soybean, Glycine max (L.) Merr. Las especies del género Amaranthus están entre las especies de malezas más abundantes y problemáticas en los sistemas de producción de soja en el medio oeste y el sur medio debido a sus características de crecimiento prolífico y su habilidad para evolucionar rápidamente resistencia a varios sitios de acción de herbicidas. Esto ha renovado el interés en la diversificación de estrategias de manejo de malezas implementando programas de manejo integrado de malezas (IWM) para manejar eficientemente a las malezas, que incluyan una mayor intercepción de luz por parte de la soja a la vez que se aumente el rendimiento de grano. Se realizaron estudios de campo a lo largo de 16 sitios-años para determinar la efectividad de la distancia entre hileras, densidad de siembra, y la estrategia de herbicidas, como componentes de un IWM en soja resistente a glufosinate. Los sitios fueron agrupados de acuerdo a las zonas óptimas de adaptación según los grupos de madurez (MGs) de la soja. Al promediar todas las regiones MG, la densidad y altura de Amaranthus, al momento de la aplicación POST del herbicida, y la densidad, la altura y la fecundidad de Amaranthus al final de la temporada, fueron reducidas en programas IWM que usaron una estrategia de herbicidas PRE seguidos por (fb) POST. Además, un tratamiento con una estrategia de herbicidas PRE fb POST aumentó la intercepción acumulativa de radiación fotosintéticamente activa (CIPAR) de la soja y subsecuentemente el rendimiento de grano de la soja al promediar todas las regiones MG. Los efectos de la distancia entre hileras y la densidad de siembra de la soja fueron altamente variables. Hileras angostas (≤ 38 cm) y una alta densidad de siembra (470,000 semillas ha−1) redujeron la altura y la fecundidad al final de la temporada en forma variable entre las regiones MG al compararse con hileras anchas (≥ 76 cm) y densidades de siembra de moderadas a bajas (322,000 a 173,000 semillas ha−1). Sin embargo, las hileras angostas y las altas densidades de siembra no redujeron la densidad de Amaranthus al momento de la aplicación de herbicida POST o al momento de la cosecha de la soja. Al promediar todas las regiones MG, la CIPAR de la soja aumentó al disminuir la distancia entre hileras e incrementar la densidad de siembra. Sin embargo, la distancia entre hileras y la densidad de siembra tuvieron efectos variables sobre el rendimiento de la soja. Adicionalmente, la CIPAR de la soja no estuvo asociada con el crecimiento ni la fecundidad de Amaranthus al final de la temporada. Una estrategia que use herbicidas PRE fb POST fue un componente necesario para que el programa IWM simultáneamente manejara malezas Amaranthus e incrementara la CIPAR de la soja y su rendimiento de grano.

Can Soybean Seeding Rate Be Used as an Integrated Component of Herbicide Resistance Management

Abstract Increased soybean seed cost has generated recent interest in reducing seeding rates to improve economic returns. However, low seeding rates result in reduced established plant stands with slower canopy development, and canopy development is an important element of integrated weed management (IWM). Field studies were conducted in 2012 and 2013 in Wisconsin to determine the trade-off between reduced seeding rates and PRE residual herbicide use for POST herbicide exposure. Soybean was planted in mid May in 38-cm-wide rows at five seeding rates ranging from 148,200 to 469,300 seeds ha−1. A PRE application of metolachlor plus fomesafen was made to half of the plots. One of two POST herbicide programs were sprayed at the V4 soybean growth stage to determine whether blending herbicide-resistant (HR) and non-HR soybean cultivars could be a practical alternative to reduce soybean seed expenses while maintaining the potential benefit of weed suppression before the POST herbicide application. An increase in seeding rate did not reduce the density or size of weeds exposed to the POST herbicide, and furthermore, end-of-season weed density and biomass were not influenced. In contrast, the use of a PRE herbicide reduced total weed density and biomass before POST application by 93 and 95%, respectively, in both years. In 2012, the season was dry early and harvest stands of 161,100 and 264,100 plants ha−1 produced 95% of the maximum yield for the PRE and no-PRE treatments, respectively. The difference was not repeated in 2013 with adequate early season rainfall. In conclusion, PRE herbicide use produced maximum yield with fewer plants per hectare by limiting early season weed competition and reduced weeds exposed to POST herbicide application thus contributing to HR management (HRM). In contrast, higher plant densities generated within the seeding rate range of this study did little to improve IWM or HRM. Nomenclature: Cloransulam; fluazifop; fomesafen; glyphosate; imazamox; metolachlor; soybean, Glycine max (L.) Merr.

Purple Deadnettle (Lamium purpureum) and Soybean Cyst Nematode Response to Cold Temperature Regimes

Abstract An experiment was conducted in growth chambers to determine the influence of cold temperature regimes, designed to simulate winter temperature conditions and spring recovery, on the interaction between purple deadnettle and soybean cyst nematode (SCN). The study was a factorial arrangement of treatments with five levels of temperature (20, 15, 10, 5, or 0 C), two levels of exposure time to the temperature (10 or 20 d), and two levels of recovery time at 20 C following exposure (0 or 20 d). In general, purple deadnettle shoot and root growth increased with temperature and time. The ability of purple deadnettle to recover from cold temperatures declined as the length of time that the plant was subjected to the cold temperature increased. SCN juveniles per gram of root at the conclusion of the temperature treatment declined as the temperature increased from 0 to 15 C, likely a result of continued purple deadnettle root growth and the inhibition of SCN hatch, growth, or development at those temperatures. SCN female, cyst, and egg production per gram of root generally increased with temperature and occurred under all temperature regimes. The results of this research indicate that, after hatching, SCN juveniles can survive a period of cold temperature inside the roots of a winter annual and continue development when transferred to warmer temperatures. Therefore, in a field environment, where fall or spring alone may not be sufficient for SCN to complete a reproductive cycle on a winter annual weed, the nematode may be able to reproduce by combining the fall and spring developmental periods. Nomenclature: Purple deadnettle, Lamium purpureum L. LAMPU; soybean cyst nematode Heterodera glycines Ichinohe

Revisiting Planting Date and Cultivar Effects on Soybean Sudden Death Syndrome Development and Yield Loss

The impact of todays optimal planting dates on sudden death syndrome (SDS) (caused by Fusarium virguliforme) development and soybean yield loss are not yet well understood. Field trials established in Hancock, Wisconsin during 2013 and 2014 investigated interactions between planting date and cultivar on SDS development and soybean yield. In 2013, disease index (DX) levels differed among cultivars, but results showed no difference between the 6 May and 24 May planting dates. Significantly lower DX levels were observed for the 17 June date. Greatest yields were found in the 6 May planting date, and yield losses were 720 (17%), 770 (20%), and 400 kg ha-1 (12%) for the 6 May, 24 May, 17 and June planting dates, respectively. In 2014, cultivars again differed for DX, but results showed highest DX levels in the 5 May planting date, with little disease observed in the 22 May and 11 June dates. Yield losses were 400 (12%) and 270 kg ha-1 (9%) for the 5 May and 22 May dates, respectively, but no difference was found in the 11 June date. Despite the most symptom development, these results suggest early May planting coupled with appropriate cultivar selection provides maximum yield potential and profitability in Wisconsin.

Weed Control in Soybean as Influenced by Residual Herbicide Use and Glyphosate-Application Timing Following Different Planting Dates

Abstract Soybean planting has occurred earlier in the Midwestern United States in recent years; however, earlier planting subjects the crop to longer durations of weed interference. This may change the optimum timing of POST glyphosate applications, or increase the need for residual herbicides applied PRE to optimize yield. A field study was conducted in 2012 and 2013 near Arlington, WI to determine the effect of planting date, residual herbicide use, and POST glyphosate timing on weed control and soybean yield. Planting dates were late April, mid-May, and early June. A PRE application of sulfentrazone plus cloransulam was applied to half the plots following each planting date. Glyphosate was applied POST to all plots at the V1, V2, V4, or R1 soybean growth stage. Planting date and glyphosate timing did not affect soybean yield in this study. However, averaged across years, planting dates, and POST glyphosate timings, yield increased from 3,280 to 3,500 kg ha−1 when a PRE herbicide with residual soil activity was used. In POST-only treatments, delaying the planting date to June decreased weed density at POST application timing from 127 to 5 plants m−2 (96%) and from 205 to 42 plants m−2 (80%) in 2012 and 2013, respectively. Where a PRE was used, total weed density at POST application timing was always less within planting date, and also declined from early to late planting date 26 to 3 plants m−2 (89%) and 23 to 6 plants m−2 (74%) in 2012 and 2013, respectively. In conclusion, both PRE herbicide use and delayed soybean planting were effective strategies to reduce the number of in-crop weeds exposed to POST glyphosate and should be considered as strategies to reduce the number of weeds exposed to POST herbicides for resistance management. Nomenclature: Glyphosate; cloransulam; sulfentrazone; soybean, Glycine max (L.) Merr. Resumen La siembra de la soja se ha dado más temprano, en años recientes en el Medio oeste de los Estados Unidos. Sin embargo, la siembra temprana expone al cultivo a períodos más largos de interferencia de malezas. Esto podría cambiar el momento óptimo para las aplicaciones POST de glyphosate, o podría incrementar la necesidad de aplicación PRE de herbicidas residuales para optimizar el rendimiento. En 2012 y 2013, cerca de Arlington, Wisconsin, se realizó un estudio de campo para determinar el efecto de la fecha de siembra, el uso de herbicidas residuales, y el momento de aplicación POST de glyphosate sobre el control de malezas y el rendimiento de la soja. Las fechas de siembra fueron: al final de Abril, la mitad de Mayo, y el inicio de Junio. Se aplicó sulfentrazone más cloransulam PRE a la mitad de las parcelas después de cada fecha de siembra. Glyphosate fue aplicado POST a todas las parcelas en los estadios de desarrollo V1, V2, V4, o R1 de la soja. La fecha de siembra y el momento de aplicación de glyphosate no afectaron el rendimiento de la soja en este estudio. Sin embargo, al promediar los años, las fechas de siembra, y los momentos de aplicación POST de glyphosate, el rendimiento incrementó de 3,280 a 3,500 kg ha−1 cuando se usó un herbicida PRE con actividad residual. En tratamientos con solo aplicaciones POST, el retrasar la fecha de siembra a Junio redujo la densidad de malezas al momento de la aplicación POST de 127 a 5 plantas m−2 (96%) y de 205 a 42 plantas m−2 (80%) en 2012 y 2013, respectivamente. Donde se usó una aplicación PRE, la densidad total de malezas al momento de la aplicación POST fue siempre menor, dentro de cada fecha de siembra, y también disminuyó de la fecha de siembra temprana a la tardía de 26 a 3 plantas m−2 (89%) y de 23 a 6 plantas m−2 (74%) en 2012 y 2013, respectivamente. En conclusión, el uso de herbicidas PRE y la siembra retrasada de la soja fueron estrategias efectivas para reducir el número de malezas dentro del cultivo expuestas a glyphosate POST y deberían ser consideradas como estrategias para reducir el número de malezas expuestas a herbicidas POST para el manejo de resistencia.