Scholarly Work - Land Resources & Environmental Sciences
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Item Impact of Puccinia punctiformis on Cirsium arvense performance in a simulated crop sequence(Frontiers Media SA, 2023-05) Chichinsky, Daniel; Larson, Christian; Menalled, Fabian D.; Seipe, Tim; Eberly, JedCirsium arvense (Canada thistle) is a perennial weed that causes significant economic losses in agriculture. An extensive rhizomatous root system makes C. arvense difficult to manage, particularly in agricultural systems that use tillage as a primary management tool. There is a need for the development of integrated weed management toolsets that include C. arvense biological controls. Puccinia punctiformis (thistle rust) is an autoecious fungal pathogen that systemically infects C. arvense, with the potential to reduce host vigor over time. The goal of this study was to integrate the P. punctiformis biocontrol with a simulated annual cropping sequence in a greenhouse environment and evaluate C. arvense’s above-and belowground biomass production, and its competitive ability. Repeated P. punctiformis inoculations produced systemically infected C. arvense stems in greenhouse pots over time. Cirsium arvense that was inoculated with P. punctiformis had 1.6 grams/pot (p = 0.0019) less aboveground biomass and 5.6 grams/pot (p< 0.001) less belowground biomass, compared to the non-inoculated (control). Puccinia punctiformis and crop competition interacted additively to lower aboveground (p<0.001) and belowground (p<0.001) C. arvense biomass more than individual use of either the biocontrol or competition alone. The aboveground competition intensity of C. arvense in a mixed crop sequence, relative to non-inoculated C. arvense grown in a monoculture, was moderately impacted by the P. punctiformis biocontrol (p = 0.0987). These results indicate that systemic infection can reduce biomass production and the competitive ability of C. arvense. Overall, P. punctiformis can be integrated into competitive annual cropping sequences with the potential to reduce C. arvense vigor over time.Item Weed Communities in Winter Wheat: Responses to Cropping Systems under Different Climatic Conditions(MDPI, 2022-06) Seipel, Tim; Ishaq, Suzanne L.; Larson, Christian; Menalled, Fabian D.Understanding the impact of biological and environmental stressors on cropping systems is essential to secure the long-term sustainability of agricultural production in the face of unprecedented climatic conditions. This study evaluated the effect of increased soil temperature and reduced moisture across three contrasting cropping systems: a no-till chemically managed system, a tilled organic system, and an organic system that used grazing to reduce tillage intensity. Results showed that while cropping system characteristics represent a major driver in structuring weed communities, the short-term impact of changes in temperature and moisture conditions appear to be more subtle. Weed community responses to temperature and moisture manipulations differed across variables: while biomass, species richness, and Simpson’s diversity estimates were not affected by temperature and moisture conditions, we observed a minor but significant shift in weed community composition. Higher weed biomass was recorded in the grazed/reduced-till organic system compared with the tilled-organic and no-till chemically managed systems. Weed communities in the two organic systems were more diverse than in the no-till conventional system, but an increased abundance in perennial species such as Cirsium arvense and Taraxacum officinale in the grazed/reduced-till organic system could hinder the adoption of integrated crop-livestock production tactics. Species composition of the no-till conventional weed communities showed low species richness and diversity, and was encompassed in the grazed/reduced-till organic communities. The weed communities of the no-till conventional and grazed/reduced-till organic systems were distinct from the tilled organic community, underscoring the effect that tillage has on the assembly of weed communities. Results highlight the importance of understanding the ecological mechanisms structuring weed communities, and integrating multiple tactics to reduce off-farm inputs while managing weeds.Item Predicted climate conditions and cover crop composition modify weed communities in semiarid agroecosystems(Wiley, 2021-10) DuPre, Mary E.; Seipel, Tim; Bourgault, Maryse; Boss, Darin L.; Menalled, Fabian D.The US Northern Great Plains is one of the largest expanses of small grain agriculture, but excessive reliance on off-farms inputs and predicted warmer and drier conditions hinder its agricultural sustainability. In this region, the use of cover crops represents a promising approach to increase biodiversity and reduce external inputs; however little information exists about how cover crop mixture composition, predicted climate and management systems could impact the performance of cover crops and weed communities. In the 4th cycle of a cover crop-wheat rotation, we experimentally increased temperature and reduced moisture as expected to occur with climate change, and assessed impacts on the presence and composition of cover crop mixtures and termination methods on weed communities. Under ambient climate conditions, mean total cover crop biomass was 43%–53% greater in a five species early-season cover crop mixture compared with a seven species mid-season mixture, and differences were less pronounced in warmer and drier conditions (19%–24%). We observed a total of 18 weed species; 13 occurring in the early-season mixture, 13 in the mid-season mixtures and 14 in the fallow treatments. Weed species richness and diversity was lower in warmer and drier treatments, and we observed a shift in weed communities due to the presence and composition of cover crop mixtures as well as climate manipulations. Overall, results suggest that adoption of cover crop mixtures in semiarid agroecosystems requires jointly addressing weed management and soil moisture retention goals, a challenge further complicated by predicted climate conditions.Item Cropping systems alter plant volatile emissions in the field through soil legacy effects(Cambridge University Press, 2022-06) Malone, Shealyn C.; Menalled, Fabian D.; Weaver, David K.; Seipel, Tim F.; Hofland, Megan L.; Runyon, Justin B.; Bourgault, Maryse; Boss, Darrin L.; Trowbridge, Amy M.Crops emit a variety of volatile organic compounds (VOCs) that serve as attractants or repellents for pests and their natural enemies. Crop rotations, off-farm chemical inputs, and mechanical and cultural tactics – collectively called cropping systems – alter soil nutrients, moisture content, and microbial communities, all of which have the potential to alter crop VOC emissions. Soil legacy effects of diversified cropping systems have been shown to enhance crop VOC emissions in greenhouse studies, but how they influence emissions under field conditions remains virtually unknown. To determine the effect of cropping systems on plant VOC emissions in the field, air samples were collected from the headspace of wheat (Triticum aestivum L. Judee) grown in simplified wheat-fallow rotations or diversified wheat-cover crop rotations where cover crops were terminated by grazing cattle. Across two growing seasons, wheat grown in rotation with fallow emitted greater amounts of Z-3-hexenyl acetate and β-ocimene, key attractants for wheat stem sawfly (Cephus cinctus Norton), a major pest of wheat. While overall VOC blends were relatively similar among cropping system during the first growing season, emissions varied substantially in the second year of this study where wheat grown in rotation with cover crops emitted substantially greater quantities of volatile compounds characteristic of abiotic stress. Below-average precipitation in the second growing season, in addition to reduced soil water content in cover crop rotations, suggests that cropping system effects on wheat VOCs may have been driven primarily by water availability, a major factor limiting crop growth in dryland agriculture. While the specific mechanisms driving changes in VOC emissions were not explicitly tested, this work shows that agricultural practices applied in one growing season can differentially influence crop VOC emissions in the next through soil legacy effects, illustrating additional avenues through which cropping systems may be leveraged to enhance pest management.Item Farming system effects on biologically mediated plant–soil feedbacks(Cambridge University Press, 2020-01) Menalled, Uriel D.; Seipel, Tim; Menalled, Fabian D.Cropping system characteristics such as tillage intensity, crop identity, crop-livestock integration and the application of off-farm synthetic inputs influence weed abundance, plant community composition and crop-weed competition. The resulting plant community, in turn, has species-specific effects on soil microbial communities which can impact the growth and competitive ability of subsequent plants, completing a plant–soil feedback (PSF) loop. Farming systems that minimize the negative impacts of PSFs on subsequent crop growth can increase the sustainability of the farming enterprise. This study sought to assess the individual and combined impact of the cropping system (certified organic-grazed, certified organic till and conventional no-till) and crop sequence [pairwise rotations with safflower (Carthamus tinctorius), yellow sweet clover (Melilotus officinalis) and winter wheat (Triticum aestivum)] on the PSF magnitude and direction. All cropping systems followed the same 5-year rotation and had completed one full rotation before soil was sampled. In a greenhouse setting, a sterile soil mix was inoculated with field soil collected from all systems and three crops. The PSF study consisted of two stages (conditioning and response phases) that mimicked the rotation stages occurring in the field. PSFs were calculated by comparing the biomass of the response phase plants grown in inoculated and uninoculated soils. The farm management system affected PSFs, inferring that tillage reduction can encourage more positive PSFs. Crop sequence did not affect PSF but interacted strongly with the farm system. As such, the effects of the farming system on PSFs are best illustrated when taken into account with the identity of the previous and current crops of a cropping sequence.Item Impacts of Dryland Cropping Systems on Ground Beetle Communities (Coleoptera: Carabidae) in the Northern Great Plains(Oxford University Press, 2021-01) DuPre, Mary E.; Weaver, David K.; Seipel, Tim F.; Menalled, Fabian D.Ground beetles are natural predators of insect pests and small seeds in agroecosystems. In semiarid cropping systems of the Northern Great Plains, there is a lack of knowledge to how ground beetles are affected by diversified cover crop rotations. In a 2-yr study (2018 and 2019), our experiment was a restricted-randomization strip-plot design, comprising summer fallow, an early-season cover crop mixture (five species), and a mid-season cover crop mixture (seven species), with three cover crop termination methods (i.e., herbicide, grazing, and haying). Using pitfall traps, we sampled ground beetles in five 48-h intervals throughout the growing season (n = 135 per year) using growing degree day (GDD) accumulations to better understand changes to ground beetle communities. Data analysis included the use of linear mixed-effects models, perMANOVA, and non-metric multidimensional scaling ordinations. We did not observe differences among cover crop termination methods; however, activity density in the early-season cover crop mixture decreased and in summer fallow increased throughout the growing season, whereas the mid-season cover crop mixture peaked in the middle of the summer. Ground beetle richness and evenness showed a nonlinear tendency, peaking in the middle of the growing season, with marginal differences between cover crops or fallow after the termination events. Also, differences in ground beetle composition were greatest in the early- and mid-season cover crop mixtures earlier in the growing season. Our study supports the use of cover crop mixtures to enhance ground beetle communities, with potential implications for pest management in dryland cropping systems.Item Plant community responses to integrating livestock into a reduced‐till organic cropping system(Wiley, 2021-03) Larson, Christian D.; Menalled, Fabian D.; Lehnhoff, Erik A.; Seipel, TimThe problems with herbicide- and tillage-based weed management in agriculture are well doc-umented and have precipitated research intofinding alternatives. Integrating livestock grazing intoorganic agroecosystems has benefits and is a viable method for terminating cover crops, yet its impacts onweed communities are largely unknown. This lack of knowledge is particularly true in semi-arid environ-ments, including the Northern Great Plains, where we conducted our research. We compared weed com-munity responses (biomass, species richness, Simpson’s diversity, composition) of a sheep-grazed organiccropping system with those of two contrasting cropping systems (high input conventional no-till, tilledorganic) across afive-year crop rotation (safflower, sweet clover, winter wheat, lentils, winter wheat). Wefound that the conventional no-till and tilled organic systems suppressed weed biomass and reduced spe-cies richness and diversity, while the grazed organic resulted in higher weed biomass, species richness, anddiversity. During thefirst two years of the study, the composition of the two organic communities were dis-tinct from the conventional no-till communities but were indistinguishable from one another. Over thefinalthree years of the study, grazed organic communities were tightly grouped and became distinct from boththe tilled and conventional communities. We found that weed biomass and diversity were highest in thesweet clover and lowest in the winter wheat. The spring annual crops, safflower and lentil, demonstratedsimilar weed biomass, species richness, and composition. Ourfindings indicate that integrating livestockinto cropping systems alters plant communities and increases the agroecosystem plant biodiversity ofsemi-arid organic farming and that specific crops interact with cropping systems to alter agroecosystemplant communities. However, the increase in weed biomass associated with our grazing treatment makesthis approach impractical as the sole weed management strategy and necessitates that integrating livestockinto semi-arid organic cropping systems must be part of a larger integrated weed management program.Item Dryland Cropping Systems, Weed Communities, and Disease Status Modulate the Effect of Climate Conditions on Wheat Soil Bacterial Communities(2020-08) Ishaq, Suzanne L.; Seipel, Tim F.; Yeoman, Carl J.; Menalled, Fabian D.Little knowledge exists on how soil bacteria in agricultural settings are impacted by management practices and environmental conditions in current and predicted climate scenarios. We assessed the impact of soil moisture, soil temperature, weed communities, and disease status on soil bacterial communities in three cropping systems: (i) conventional no-till (CNT) systems utilizing synthetic pesticides and herbicides, (ii) USDA-certified tilled organic (OT) systems, and (iii) USDA-certified organic systems with sheep grazing (OG). Sampling date within the growing season and associated soil temperature and moisture exerted the greatest effect on bacterial communities, followed by cropping system, Wheat streak mosaic virus (WSMV) infection status, and weed community. Soil temperature was negatively correlated with bacterial richness and evenness, while soil moisture was positively correlated with bacterial richness and evenness. Soil temperature and soil moisture independently altered soil bacterial community similarity between treatments. Inoculation of wheat with WSMV altered the associated soil bacteria, and there were interactions between disease status and cropping system, sampling date, and climate conditions, indicating the effect of multiple stressors on bacterial communities in soil. In May and July, cropping system altered the effect of climate change on the bacterial community composition in hotter conditions and in hotter and drier conditions compared to ambient conditions, in samples not treated with WSMV. Overall, this study indicates that predicted climate modifications as well as biological stressors play a fundamental role in the impact of cropping systems on soil bacterial communities.Item Herbivore-induced volatile emissions are altered by soil legacy effects in cereal cropping systems(2020-08) Malone, Shealyn C.; Weaver, David K.; Seipel, Tim F.; Menalled, Fabian D.; Hofland, Megan L.; Runyon, Justin B.; Trowbridge, Amy M.Aims Soil properties, including microbial composition and nutrient availability, can influence the emissions of plant volatile organic compounds (VOCs) that serve as host-location cues for insect pests and their natural enemies. Agricultural practices have profound effects on soil properties, but how these influence crop VOCs remains largely unknown. The aim of this study was to investigate the effect of agricultural practices on constitutive and herbivore-induced VOC emissions by a major staple crop through soil legacy effects. Methods In a full factorial experiment, we measured VOC emissions by wheat (Triticum aestivum) grown in soil inoculum from wheat-fallow or wheat-cover crop rotations that was subjected to feeding by larval Cephus cinctus. Results Under herbivory, plants grown in cover crop inoculum emitted greater total VOCs, including higher concentrations of 2-pentadecanone, an insect repellent, and nonanal, a compound important in the recruitment of natural enemies. Plants grown in fallow inoculum showed no differences in emissions whether under herbivory or not. Soil inoculum did not influence VOC emissions of plants in the absence of larval feeding. Conclusions These results suggest that agricultural practices influence crop VOC emissions through soil legacy effects. Additionally, crops grown in wheat-fallow rotations may be less successful recruiting natural enemies of pests through herbivore-induced VOC signaling. Abbreviations Volatile organic compounds (VOCs); herbivore-induced plant volatiles (HIPV); green leaf volatiles (GLVs); northern Great Plains (NGP); wheat stem sawfly (WSS); gas chromatography-mass spectrometry (GC-MS); non-metric multidimensional scaling (NMDS); generalized linear mixed-effects model (GLMM).Item Supporting Beneficial Insects for Agricultural Sustainability: The Role of Livestock-Integrated Organic and Cover Cropping to Enhance Ground Beetle (Carabidae) Communities(2020-08) Adhikari, Subodh; Menalled, Fabian D.Ground beetles (Carabidae) are beneficial insects providing ecosystem services by regulating insect pests and weed seeds. Despite several studies conducted on ground beetles worldwide, there is a lack of knowledge on how these insects are affected by differently managed organic systems (e.g., tillage-based versus grazed-based) compared to that of chemical-based no-tillage conventional cropping systems. In a 5-year (2013–2017) study, we assessed the ground beetle communities in cover crops and winter wheat (Triticum aestivium L.) in Montana, USA, with three contrasting cropping systems: a chemically managed no-tillage, a tillage-based organic, and a livestock-integrated organic with reduced tillage. The first three years (i.e., 2013–2015) corresponded to the transition to organic period, while the last two (i.e., 2016–2017) were conducted in United States Department of Agriculture (USDA) organic-certified tillage-based and livestock-integrated organic systems. The experiment was designed with three management systems across three blocks as the whole plot variable and 5-year rotation of crop phases as the subplot variable. Using pitfall traps, we sampled ground beetles across all cover crop and winter wheat subplots for five years (n = 450). The data were analyzed using mixed effects models and PERMANOVA and visualized with non-metric multidimensional scaling ordination. Our study indicated that organically managed farms, whether tilled or grazed, enhance activity density, species richness, diversity, and evenness of ground beetles in the dryland row crop productions. Also, irrespective of farming system, cover crops supported higher species richness, diversity, and evenness of ground beetles than winter wheat. The ground beetle communities were mostly similar during the transition to organic period. However, during the established organic phase, cropping systems acted as contrasting ecological filters and beetle communities became dissimilar. Cover cropping affected ground beetle communities positively not only in organically managed systems but also in chemical-based conventional systems. Our study provides evidence supporting the adoption of ecologically-based cropping systems such as crop-livestock integration, organic farming, and cover cropping to enhance beneficial insects and their pest-regulation services.
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