Horticulture Commons^™

Resistance Screening And Association Mapping For Resistance To The Downy Mildew Pathogen Of Spinach, Dotun Olaoye

Graduate Theses and Dissertations

Spinach is an important cool leafy vegetable cultivated around the world, with large scale production in California and Arizona in the U.S. Spinach is a highly nutritious vegetable beneficial in the human diet. Spinach is affected by a number of biotic stressors. Downy mildew, caused by the oomycete pathogen Peronospora effusa, is a major threat to spinach as it affects the leaf quality and impacts the economic value of spinach. Several efforts have led to the development of resistant genotypes/cultivars to this pathogen. However, few studies have examined the genetics of resistance to the downy mildew pathogen in detail. This …

Long-Term Changes In Soil Surface Properties As Affected By Management Practices In A Wheat-Soybean, Double-Crop System, Machaela Morrison

Crop, Soil and Environmental Sciences Undergraduate Honors Theses

Long-term agricultural sustainability and productivity are controlled by the integrative effects of different management practices on the soil. Many Arkansas producers use the double-crop system to grow soybeans [Glycine max (L.) Merr] and wheat (Triticum aestivum L.). Studying combinations of different, non-traditional, alternative agricultural techniques may help producers better understand the long-term implications of various management practice options on sustainability and productivity. The objective of this study was to evaluate the effects of agricultural management practices, including residue level, tillage, irrigation, and burning, and soil depth on the change in various soil properties from 2010 to 2020 in …

The Effect Of Anionic Surfactants On Herbicide Mixtures And Solutions, Ely Daniel Anderson

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Herbicide mixtures are popular for farmers to delay the evolution of herbicide-resistant biotypes from occurring and control existing herbicide-resistant weeds. Glufosinate is a contact herbicide that has been observed as a mixture partner with many herbicides. In many cases, antagonistic interactions have occurred when using glufosinate in mixture with other herbicides. The antagonistic interactions have resulted in applications with incomplete weed control. Adjuvants have been known to impact an herbicide application by increasing herbicide penetration, spreadability, and efficacy. Adjuvants added to glufosinate mixtures can impact spray applications and increase weed control. The objectives of this research were: (1) investigate the …

Evaluation Of Irrigation And Nutrient Management Strategies In Rice Using Alternative Irrigation Methods, Justin Lee Chlapecka

Graduate Theses and Dissertations

As water resources gain value across the Mid-South, alternative irrigation strategies of rice (Oryza sativa L.) have garnered increasing attention. In 2015, an estimated 1.7% of Arkansas rice hectarage used alternate wetting and drying (AWD) irrigation and 0.9% used furrow irrigation. As of 2020, 2.5% used AWD and 16.9% used furrow irrigation, the latter accounting for near 99,000 ha in Arkansas. Little information exists in the scientific literature in relation to management of rice grown in the Mid-South without a conventional flood. This fact coupled with the rapid adoption rate, especially for furrow-irrigated rice (FIR), during the last five years …

Phenotypic Plasticity Of Diverse Sorghum Varieties In Response To Nitrogen Deficit Stress, Mackenzie Zwiener

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

The movement of nutrients from old vegetative tissue to young leaves and reproductive organs is known as senescence. Senescence can be influenced by the environment of a plant, such as, drought, heat, and nutrient stress. These environmental stressors can also influence canopy architecture. Crop canopy consists of several traits including: leaf number, angle, length and width. Past research in crops like maize and rice have shown significant influences of more erect leaves, including, the ability for increased planting density, which optimizes light interception and increases yield. In a field trial of a sorghum association panel including 345 different sorghum varieties …

Nozzle Selection And Adjuvant Impact On The Efficacy Of Glyphosate And Ppo-Inhibiting Herbicide Tank-Mixtures, Jesaelen G. Moraes, Thomas R. Butts, Vitor M. Anunciato, Joe D. Luck, Wesley C. Hoffmann, Ulisses R. Antuniassi, Greg R. Kruger

Department of Agronomy and Horticulture: Faculty Publications

PPO-inhibiting herbicides in combination with glyphosate for postemergence applications is a common approach to manage glyphosate- and ALS-inhibitor-resistant weeds. PPO-inhibitors can reduce glyphosate translocation when applied in tank-mixtures, but adjuvants may be used to overcome this effect. Additionally, optimal droplet size may be affected by tank-mixtures of different herbicides and it can be crucial to herbicide efficacy. Field and greenhouse studies were conducted to investigate the impact of nozzle selection and adjuvants on weed control and interactions when applying PPO-inhibitors (fomesafen or lactofen) alone or in tank-mixture with glyphosate to five weed species using six nozzle types. Ultra-coarse droplets were …

Maize Nitrogen Management Using Reactive Sensor And Proactive Maize-N Model Via Fertigation, Mohammed Abdulridha Naser

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Applying a portion of total nitrogen (N) during the growing season has the potential to improve nitrogen use efficiency (NUE) by achieving greater synchrony between N supply and crop N demand, allowing for responsive adjustments to actual field conditions. Three studies from 2017-2019 evaluated using reactive sensor and proactive Maize-N model for determining in-season N requirements via fertigation in corn. The first study evaluated the integration of reactive sensor and proactive Maize-N model for determining the timing and rate of in-season N via fertigation. Overall, reactive and proactive fertigation treatments reduced total N applied by 35 to 65 kg N …

The Influence Of Adjuvants On Physical Properties, Droplet-Size, And Efficacy Of Glufosinate And Dicamba Plus Glyphosate Solutions, Estefania Gomiero Polli

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Adjuvants are used in agriculture to improve herbicide activity or application performance. The addition of adjuvants to herbicide solution can enhance its penetration, wettability, and evaporation rates by altering density, viscosity, contact angle between the droplet and plant surface, and droplet surface tension. Furthermore, those alterations in the physical properties of the herbicide solution can result in changes in the droplet-size distribution that directly impact herbicide efficacy. The adoption of glufosinate-based herbicide programs has increased with the widespread occurrence of glyphosate-resistance (GR) weeds in recent years. Also, tank mixture of dicamba and glyphosate has been largely adopted for broad-spectrum weed …

Comparing A Mixed Model Approach To Traditional Stability Estimators For Mapping Genotype By Environment Interactions And Yield Stability In Soybean [Glycine Max (L.) Merr.], Mary M. Happ, George L. Graef, Haichuan Wang, Reka Howard, Luis Posadas, David L. Hyten

Department of Agronomy and Horticulture: Faculty Publications

Identifying genetic loci associated with yield stability has helped plant breeders and geneticists begin to understand the role and influence of genotype by environment (GxE) interactions in soybean [Glycine max (L.) Merr.] productivity, as well as other crops. Quantifying a genotype’s range of performance across testing locations has been developed over decades with dozens of methodologies available. This includes directly modeling GxE interactions as part of an overall model for yield, as well as methods which generate overall yield “stability” values from multi-environment trial data. Correspondence between these methods as it pertains to the outcomes of genome wide association studies …

Soil Erosion Modelling: A Bibliometric Analysis, Nejc Bezak, Matjǎz Mikǒs, Pasquale Borrelli, Christine Alewell, Dinesh Panday, Panos Panagos, 59 Co-Authors

Department of Agronomy and Horticulture: Faculty Publications

Soil erosion can present a major threat to agriculture due to loss of soil, nutrients, and organic carbon. Therefore, soil erosion modelling is one of the steps used to plan suitable soil protection measures and detect erosion hotspots. A bibliometric analysis of this topic can reveal research patterns and soil erosion modelling characteristics that can help identify steps needed to enhance the research conducted in this field. Therefore, a detailed bibliometric analysis, including investigation of collaboration networks and citation patterns, should be conducted. The updated version of the Global Applications of Soil Erosion Modelling Tracker (GASEMT) database contains information about …

Mental Model-Based Repeated Multifaceted (Mrm) Intervention Design: A Conceptual Framework For Improving Preventive Health Behaviors And Outcomes, Mazbahul G. Ahamad, Fahian Tanin

Department of Agronomy and Horticulture: Faculty Publications

Objective: Field interventions employed to improve preventive health behaviors and outcomes generally use well established approaches; however, recent studies have reported that health education and promotional interventions have little to no impact on health behaviors, especially in low- and middle-income countries. We aimed to develop a conceptual framework to improve intervention designs that would internalize these concerns and limitations.

Results: We identified three major experimental design- and implementation-related concerns associated with mental models, including the balance between the treatment and control groups, the treatment group’s willingness to adopt suggested behaviors, and the type, length, frequency, intensity, and sequence of treatments. …

Grass Bud Responses To Fire In A Semiarid Savanna System, Quinn A. Hiers, Morgan L. Treadwell, Matthew B. Dickinson, Kathleen L. Kavanagh, Alexandra G. Lodge, Heath D. Starns, Doug R. Tolleson, Dirac Twidwell, Carissa L. Wonkka, William E. Rogers

Department of Agronomy and Horticulture: Faculty Publications

Increasingly, land managers have attempted to use extreme prescribed fire as a method to address woody plant encroachment in savanna ecosystems. The effect that these fires have on herbaceous vegetation is poorly understood. We experimentally examined immediate (<24 hr) bud response of two dominant graminoids, a C₃ caespitose grass, Nassella leucotricha, and a C₄ stoloniferous grass, Hilaria belangeri, following fires of varying energy (J/m² ) in a semiarid savanna in the Edwards Plateau ecoregion of Texas. Treatments included high- and low-energy fires determined by contrasting fuel loading and a no burn (control) treatment. Belowground axillary buds were counted and their activities classified to determine immediate effects …

Effects Of Intraguild Interactions On Anticarsia Gemmatalis And Chrysodeixis Includens Larval Fitness And Behavior In Soybean, Sabrina Ongaratto, Edson Ll Baldin, Thomas E. Hunt, Debora G. Montezano, Emily A. Robinson, Maria C. Dos Santos

Department of Agronomy and Horticulture: Faculty Publications

BACKGROUND: Crop pest management requires an understanding of the complex interactions among species that potentially impact crop yield. In soybean, the velvetbean caterpillar, Anticarsia gemmatalis (Hübner), and the soybean looper, Chrysodeixis includens (Walker), are described as key pests, sharing the same feeding guild. We assessed the intraguild interactions of these species under laboratory conditions. Fitness cost study was conducted to examine the influence of competition on insect development. A video tracking system was used to evaluate behavioral parameters during larval interactions in scenarios with and without food availability. RESULTS: In the fitness cost assay, pupal weight was not significantly affected, …

Microbial Community Field Surveys Reveal Abundant Pseudomonas Population In Sorghum Rhizosphere Composed Of Many Closely Related Phylotypes, Dawn Chiniquy, Elle M. Barnes, Jinglie Zhou, Kyle Hartman, Xiaohui Li, Amy Sheflin, Ellen Marsh, Jessica Prenni, Adam M. Deutschbauer, Daniel P. Schachtman, Susannah G. Tringe

Department of Agronomy and Horticulture: Faculty Publications

While the root-associated microbiome is typically less diverse than the surrounding soil due to both plant selection and microbial competition for plant derived resources, it typically retains considerable complexity, harboring many hundreds of distinct bacterial species. Here, we report a time-dependent deviation from this trend in the rhizospheres of field grown sorghum. In this study, 16S rRNA amplicon sequencing was used to determine the impact of nitrogen fertilization on the development of the root-associated microbiomes of 10 sorghum genotypes grown in eastern Nebraska. We observed that early rhizosphere samples exhibit a significant reduction in overall diversity due to a high …

Utility Of Climatic Information Via Combining Ability Models To Improve Genomic Prediction For Yield Within The Genomes To Fields Maize Project, Diego Jarquin, Natalia De Leon, Cinta Romay, Martin Bohn, Edward S. Buckler, Ignacio Ciampitti, Jode Edwards, David Ertl, Sherry Flint-Garcia, Michael A. Gore, Christopher Graham, Candice N. Hirsch, James B. Holland, David Hooker, Shawn M. Kaeppler, Joseph Knoll, Elizabeth C. Lee, Carolyn J. Lawrence-Dill, Jonathan P. Lynch, Stephen P. Moose, Seth C. Murray, Rebecca Nelson, Torbert Rocheford, James C. Schnable, Patrick S. Schnable, Margaret Smith, Nathan Springer, Peter Thomison, Mitch Tuinstra, Randall J. Wisser, Wenwei Xu, Jianming Yu, Aaron Lorenz

Department of Agronomy and Horticulture: Faculty Publications

Genomic prediction provides an efficient alternative to conventional phenotypic selection for developing improved cultivars with desirable characteristics. New and improved methods to genomic prediction are continually being developed that attempt to deal with the integration of data types beyond genomic information. Modern automated weather systems offer the opportunity to capture continuous data on a range of environmental parameters at specific field locations. In principle, this information could characterize training and target environments and enhance predictive ability by incorporating weather characteristics as part of the genotype-by-environment (G×E) interaction component in prediction models. We assessed the usefulness of including weather data variables …

A Microbiome Engineering Framework To Evaluate Rhizobial Symbionts Of Legumes, Kenjiro W. Quides, Hagop S. Atamian

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Background

For well over a century, rhizobia have been recognized as effective biofertilizer options for legume crops. This has led to the widespread use of rhizobial inoculants in agricultural systems, but a recurring issue has emerged: applied rhizobia struggle to provide growth benefits to legume crops. This has largely been attributed to the presence of soil rhizobia and has been termed the ‘rhizobial competition problem.’

Scope

Microbiome engineering has emerged as a methodology to circumvent the rhizobial competition problem by creating legume microbiomes that do not require exogenous rhizobia. However, we highlight an alternative implementation of microbiome engineering that focuses …

Effects Of Foliar Fungicide On Yield, Micronutrients, And Cadmium In Grains From Historical And Modern Hard Winter Wheat Genotypes, Hollman Motta-Romero, Ferdinand Niyongira, Jeffrey D. Boehm Jr, Devin J. Rose

Department of Agronomy and Horticulture: Faculty Publications

Plant breeding and disease management practices have increased the grain yield of hard winter wheat (Triticum aestivum L.) adapted to the Great Plains of the United States during the last century. However, the effect of genetic gains for seed yield and the application of fungicide on the micronutrient and cadmium (Cd) concentration in wheat grains is still unclear. The objectives of this study were to evaluate the effects of fungicide application on the productivity and nutritional quality of wheat cultivars representing 80 years of plant breeding efforts. Field experiments were conducted over two crop years (2017 and 2018) with eighteen …

Wayne E. Sabbe Arkansas Soil Fertility Studies 2020, Nathan A. Slaton

Arkansas Agricultural Experiment Station Research Series

Rapid technological changes in crop management and production require that the research efforts be presented in an expeditious manner. The contributions of soil fertility and fertilizers are major production factors in all Arkansas crops. The studies described within will allow producers to compare their practices with the university’s research efforts. Additionally, soil-test data and fertilizer sales are presented to allow comparisons among years, crops, and other areas within Arkansas.

Cultivating Hops For Cone Production In Nebraska, Stacy A. Adams

Department of Agronomy and Horticulture: Faculty Publications

The hop cone is the primary product of agronomic value when growing Humulus lupulus L. (common hop). Cones are modified stem and leaf structures that protect the female flower cluster that forms chemical compounds important for flavoring beer and other uses. The majority of hops in the United States (~96%) is grown in the states of Washington, Oregon, and Idaho. Hops can be grown in very diverse climates, but it is the climatic consistency of the Pacific NW that provides product consistency and reasoning commercial hops production is prevalent in the region. Hops is a niche crop outside of the …

Novel And Transgressive Salinity Tolerance In Recombinant Inbred Lines Of Rice Created By Physiological Coupling-Uncoupling And Network Rewiring Effects, Isaiah C.M. Pabuayon, Ai Kitazumi, Kevin R. Cushman, Rakesh Kumar Singh, Glenn B. Gregorio, Balpreet Dhatt, Masoud Zabet-Moghaddam, Harkamal Walia, Benildo G. De Los Reyes

Department of Agronomy and Horticulture: Faculty Publications

The phenomenon of transgressive segregation, where a small minority of recombinants are outliers relative to the range of parental phenotypes, is commonly observed in plant breeding populations. While this phenomenon has been attributed to complementation and epistatic effects, the physiological and developmental synergism involved have not been fully illuminated by the QTL mapping approach alone, especially for stress adaptive traits involving highly complex interactions. By systems-level profiling of the IR29 × Pokkali recombinant inbred population of rice, we addressed the hypothesis that novel salinity tolerance phenotypes are created by reconfigured physiological networks due to positive or negative coupling-uncoupling of developmental …

Evaluation Of Soil Moisture Sensing Technologies In Silt Loam And Loamy Sand Soils: Assessment Of Performance, Temperature Sensitivity, And Site- And Sensor-Specific Calibration Functions, K. Sharma, Sibel Irmak, M. S. Kukal, M. C. Vuran, Amit J. Jhala, Xia Qiao

Department of Agronomy and Horticulture: Faculty Publications

Reliable soil moisture information is vital for optimal irrigation management, farm-level agronomic decision-making, hydrologic studies, and cropping systems modeling. A wide range of soil moisture sensing technologies is commercially available, but their performance must be evaluated for diverse conditions of use. In this research, we investigated nine soil moisture sensors based on time-domain reflectometry, capacitance, and electrical resistance principles in production field conditions with two installation orientations, i.e., vertical (V) and horizontal (H), in two soils (silt loam and loamy sand) and two growing seasons (2017 and 2018). Performance parameters deduced from the 2017 datasets revealed that sensor type and …

Corn Residue Baling And Grazing Impacts On Corn Yield Under Irrigated Conservation Tillage Systems, Sabrina J. Ruis, Charles Burr, Humberto Blanco-Canqui, Brian Olson, Mark Reiman, Daran Rudnick, Johnna Baller, Kathryn J. Hanford

Department of Agronomy and Horticulture: Faculty Publications

Crop residue grazing or baling is common in the western Corn Belt. However, its impacts on subsequent crop yields under different irrigation levels and tillage systems are unclear. We investigated the impacts of corn (Zea mays L.) residue baling and cattle grazing on soil compaction, water content, and corn yield under full and limited irrigated no-till in Nebraska during three years. In Years 2 and 3, an additional tillage treatment (strip till) was implemented to evaluate its effects on grain yield under the above treatments. Residue removal effects on compaction and water content did not vary with irrigation level. …

Seedextractor: An Open-Source Gui For Seed Image Analysis, Feiyu Zhu, Puneet Paul, Waseem Hussain, Kyle Wallman, Balpreet K. Dhatt, Jaspreet Sandhu, Larissa Irvin, Gota Morota, Hongfeng Yu, Harkamal Walia

Department of Agronomy and Horticulture: Faculty Publications

Accurate measurement of seed size parameters is essential for both breeding efforts aimed at enhancing yields and basic research focused on discovering genetic components that regulate seed size. To address this need, we have developed an open source graphical user interface (GUI) software, SeedExtractor that determines seed size and shape (including area, perimeter, length, width, circularity, and centroid), and seed color with capability to process a large number of images in a time-efficient manner. In this context, our application takes 2 s for analyzing an image, i.e., significantly less compared to the other tools. As this software is open-source, it …

Landscape Performance Of Ebony Crepe Myrtle Cultivars In Low-Input Landscapes In North-Central Texas, Derald A. Harp, Kevin Chretien, Mariah Brown, Curtis Jones, Jose Lopez

Faculty Publications

The Ebony series of crepe myrtle (Lagerstroemia indica) cultivars includes several (Ebony Embers, Ebony Fire, Ebony Flame, Ebony Glow, and Ebony and Ivory), marketed today under the Black Diamond® brand. These are relatively new crepe myrtle cultivars unique for their dark foliage, but with little information concerning their performance in north-central Texas, especially in low-input landscapes. The study was conducted from 2014 to 2017 at three locations in north-central Texas with three soil types, an acidic fine sandy loam, a neutral pH silt loam, and an alkaline heavy clay. Although soils and environmental conditions caused variations between sites, …

Soil Properties Limiting Vegetation Establishment Along Roadsides, Shad D. Mills, Martha Mamo, Sabrina J. Ruis, Humberto Blanco-Canqui, Walter Schacht, Tala Awada, Xu Li, Pamela Sutton

Department of Agronomy and Horticulture: Faculty Publications

Roadside vegetation provides a multitude of ecosystem services, including pollutant remediation, runoff reduction, wildlife habitat, and aesthetic scenery. Establishment of permanent vegetation along paved roads after construction can be challenging, particularly within 1 m of the pavement. Adverse soil conditions could be one of the leading factors limiting roadside vegetation growth. In this study, we assessed soil physical and chemical properties along a transect perpendicular to the road at six microtopographic positions (road edge, shoulder, side slope, ditch, backslope, and field edge) along two highway segments near Beaver Crossing and Sargent, NE. At the Beaver Crossing site, Na concentration was …

Intervention Of Climate‐Smart Practices In Wheat Under Rice‐ Wheat Cropping System In Nepal, Jamma Jaya Gairhe, Mandeep Adhikari, Deepak Ghimire, Arun Kjatri-Chhetri, Dinesh Panday

Department of Agronomy and Horticulture: Faculty Publications

Besides a proper agronomic management followed by Nepalese farmers, wheat (Triticum aestivum L.) production has been severely affected by changing climate. There are many interventions, including climate‐smart practices, to cope with this situation and possibly enhance crop and soil productivity. Field experiments were set up in a randomized complete block design with six treatments (TRT) with four replications in three locations (LOC) during wheat‐growing seasons in Nepal from 2014 to 2016. Treatments included (i) Controlled Practice (CP), (ii) Improved Low (IL), (iii) Improved High (IH), (iv) Climate Smart Agriculture Low (CSAL), (v) Climate Smart Agriculture Medium (CSAM), and (vi) Climate …

A Bumper Crop Of Snps In Soybean Through High-Density Genotyping-By-Sequencing (Hd-Gbs), Davoud Torkamaneh, Jerome Laroche, Brian Boyle, David L. Hyten, Fancois Belzile

Department of Agronomy and Horticulture: Faculty Publications

No abstract provided.

Genome-Wide Discovery Of Natural Variation In Pre-Mrna Splicing And Prioritising Causal Alternative Splicing To Salt Stress Response In Rice, Huihui Yu, Qian Du, Malachy Campbell, Bin Yu, Harkamal Walia, Chi Zhang

Department of Agronomy and Horticulture: Faculty Publications

Pre-mRNA splicing is an essential step for the regulation of gene expression. In order to specifically capture splicing variants in plants for genome-wide association studies (GWAS), we developed a software tool to quantify and visualise Variations of Splicing in Population (VASP). VASP can quantify splicing variants from short-read RNA-seq datasets and discover genotype-specific splicing (GSS) events, which can be used to prioritise causal pre-mRNA splicing events in GWAS. We applied our method to an RNA-seq dataset with 328 samples from 82 genotypes from a rice diversity panel exposed to optimal and saline growing conditions. In total, 764 significant GSS events …

Gwas Revealed Effect Of Genotype × Environment Interactions For Grain Yield Of Nebraska Winter Wheat, Shamseldeen Eltaher, P Stephen Baenziger, Vikas Belamkar, Hamdy A. Emara, Ahmed A. Nower, Khaled F.M. Salem, Ahmad M. Alqudah, Ahmed Sallam

Department of Agronomy and Horticulture: Faculty Publications

Background: Improving grain yield in cereals especially in wheat is a main objective for plant breeders. One of the main constrains for improving this trait is the G × E interaction (GEI) which affects the performance of wheat genotypes in different environments. Selecting high yielding genotypes that can be used for a target set of environments is needed. Phenotypic selection can be misleading due to the environmental conditions. Incorporating information from phenotypic and genomic analyses can be useful in selecting the higher yielding genotypes for a group of environments. Results: A set of 270 F_3:6 wheat genotypes in the …

Seed-Shattering Phenology At Soybean Harvest Of Economically Important Weeds In Multiple Regions Of The United States. Part 2: Grass Species, Lauren M. Schwartz-Lazaro, Lovreet S. Shergill, Jeffrey A. Evans, Muthukumar V. Bagavathiannan, Shawn C. Beam, Mandy D. Bish, Jason A. Bond, Kevin W. Bradley, William S. Curran, Adam S. Davis, Wesley J. Everman, Michael L. Flessner, Steven C. Haring, Nicholas R. Jordan, Nicholas E. Korres, John L. Lindquist, Jason K. Norsworthy, Tameka L. Sanders, Larry E. Steckel, Mark J. Vangessel, Blake Young, Steven B. Mirsky

Department of Agronomy and Horticulture: Faculty Publications

Seed shatter is an important weediness trait on which the efficacy of harvest weed seed control (HWSC) depends. The level of seed shatter in a species is likely influenced by agroecological and environmental factors. In 2016 and 2017, we assessed seed shatter of eight economically important grass weed species in soybean [Glycine max (L.) Merr.] from crop physiological maturity to 4 wk after maturity at multiple sites spread across 11 states in the southern, northern, and mid-Atlantic United States. From soybean maturity to 4 wk after maturity, cumulative percent seed shatter was lowest in the southern U.S. regions and increased …