Field studies were conducted on certified organic land in Lafayette and Vincennes, IN, in 2023 to determine the impact of different between-row weed control methods on weed suppression and sweetpotato yield. Between-row treatments consisted of organic buckwheat (108 kg ha−1) broadcast seeded immediately after sweetpotato transplanting followed by silage tarping from 3 wk after transplanting (WATr) through harvest, organic buckwheat (108 kg ha−1) broadcast seeded 3 WATr and terminated 7 WATr, and cultivation as a grower standard. Weed density at 6 WATr was 0, 184, and 162 plants m−2 for the silage tarping, living mulch buckwheat, and cultivation treatments, respectively. Total yield was 11,048 kg ha−1 for the living mulch buckwheat, 19,792 kg ha−1 for the cultivation, and 17,814 kg ha−1 for the tarping treatments. Tarping effectively suppressed weeds and produced sweetpotato yields comparable to cultivation, indicating the potential for use by organic growers. When buckwheat was grown between rows 3 to 7 WATr, sweetpotato yield was lower than it was with tarping and cultivation. These results suggest that researchers should be evaluating tarps for small-acreage farmers as a weed management strategy.

Organic sweetpotato growers have limited effective weed management options, and most rely on in-season between-row cultivation and hand weeding, which are time consuming, are costly, and deteriorate soil quality. Studies were conducted at the Samuel G. Meigs Horticulture Research Farm, Lafayette, IN, and at the Southwest Purdue Agricultural Center, Vincennes, IN, in 2022 and 2023 to determine the effects of in-row plant spacing and cultivar selection on weed suppression and organic sweetpotato yield. The experiment was a split-split plot design, with in-row spacings of 20, 30, and 40 cm as the main plot factor, weeding frequency (critical weed-free period and weed-free) as the subplot factor, and sweetpotato cultivar (‘Covington’ and ‘Monaco’) as the sub-subplot factor. However, in 2022, we evaluated only in-row spacing and weeding frequency because of the poor establishment of ‘Monaco’. In 2023, sweetpotato canopy at 5 wk after transplanting (WAP) decreased as in-row spacing increased from 20 to 40 cm, and sweetpotato canopy cover of ‘Monaco’ (62%) was greater than that of ‘Covington’ (44%). In-row spacing did not affect weed density at 4, 5, and 6 WAP. As in-row spacing increased from 20 to 40 cm, total sweetpotato yield pooled across both locations in 2023 decreased from 30,223 to 21,209 kg ha−1 for ‘Covington’ and from 24,370 to 20,848 kg ha−1 for ‘Monaco’; however, jumbo yield increased for both cultivars. Findings from this study suggest that an in-row spacing of 20 cm may provide greater yield than the standard spacing of 30 cm for both ‘Monaco’ and ‘Covington’.

Sweetpotato [Ipomoea batatas (L.) Lam.] is a staple crop that provides nutritional benefits to humans globally, but it is subject to yield loss when competing with weeds, especially during the early stage of establishment. Yield loss can vary widely based on the cultivar, production environment, weed species, and management techniques. To address this challenge, we conducted field research at the Samuel G. Meigs Horticulture Research Farm, Lafayette, IN, and at the Southwest Purdue Agricultural Center, Vincennes, IN, in 2022 to determine the effect of sweetpotato cultivar on the critical weed-free period. The experiment was a split-plot design, with weed-free interval treatments as the main plot factor and cultivar as the subplot factor. The three cultivars used were ‘Covington’, ‘Monaco’, and ‘Murasaki’. Weeds were removed by hand and allowed to establish and compete with the crop beginning at 0, 14, 21, 28, 35, or 42 d after transplanting (DAP). As the weed-free interval increased from 0 to 42 DAP, predicted total yield increased from 19 kg ha−1 to 20,540 kg ha−1 for Covington, 3 kg ha−1 to 11,407 kg ha−1 for Monaco, and 125 kg ha−1 to 13,460 kg ha−1 for Murasaki at the Lafayette location. At Vincennes, as the weed-free interval increased from 0 to 42 DAP, predicted total yield increased from 14,664 kg ha−1 to 33,905 kg ha−1 for Covington, 4,817 kg ha−1 to 18,059 kg ha−1 for Monaco, and 12,735 kg ha−1 to 21,105 kg ha−1 for Murasaki. A threshold of ≤10% total yield reduction was achieved by maintaining sweetpotatoes weed-free 24 DAP for Covington, 20 DAP for Murasaki, and 33 DAP for Monaco.

Field experiments were conducted in 2017 and 2018 at two locations in Indiana to evaluate the influence of cover crop species, termination timing, and herbicide treatment on winter and summer annual weed suppression and corn yield. Cereal rye and canola cover crops were terminated early or late (2 wk before or after corn planting) with a glyphosate- or glufosinate-based herbicide program. Canola and cereal rye reduced total weed biomass collected at termination by up to 74% and 91%, in comparison to fallow, respectively. Canola reduced horseweed density by up to 56% at termination and 57% at POST application compared to fallow. Cereal rye reduced horseweed density by up to 59% at termination and 87% at POST application compared to fallow. Canola did not reduce giant ragweed density at termination in comparison to fallow. Cereal rye reduced giant ragweed density by up to 66% at termination and 62% at POST application. Termination timing had little to no effect on weed biomass and density reduction in comparison to the effect of cover crop species. Cereal rye reduced corn grain yield at both locations in comparison to fallow, especially for the late-termination timing. Corn grain yield reduction up to 49% (4,770 kg ha–1) was recorded for cereal rye terminated late in comparison to fallow terminated late. Canola did not reduce corn grain yield in comparison to fallow within termination timing; however, late-terminated canola reduced corn grain yield by up to 21% (2,980 kg ha–1) in comparison to early-terminated fallow. Cereal rye can suppress giant ragweed emergence, whereas canola is not as effective at suppressing large-seeded broadleaves such as giant ragweed. These results also indicate that early-terminated cover crops can often result in higher corn grain yields than late-terminated cover crops in an integrated weed management program.

The objective of this research was to determine the potential use of commercially available multispectral images to detect weeds at low densities during the critical period of weed control. Common lambsquarters seedlings were transplanted into plots of glyphosate-resistant corn at 0, 1, 2, and 4 plants/m2 at two sites, Agronomy Center for Research and Extension (ACRE) and Meig's Horticultural Research Farm at the Throckmorton–Purdue Agricultural Center (TPAC), in Indiana. Aerial multispectral images (12 to 16 cm pixel resolution) were taken 18 and 32 days after planting (DAP) at ACRE and 19 and 32 DAP at TPAC. Corn and common lambsquarters could not be reliably detected and differentiated at either site when weeds were 9 cm or less in height. However, economic threshold densities (2 and 4 plants/m2) of common lambsquarters could be distinguished from weed-free plots at TPAC when weeds were 17 cm in height. At this height, common lambsquarters plants were beyond the optimal height for glyphosate application, but could still be readily controlled with higher rates. Results from this study indicate that commercially available multispectral aerial imagery at current spatial resolutions does not provide consistently reliable data for detection of early season weeds in glyphosate-resistant corn cropping systems. Additional refinement in sensor spatial and spectral resolution is necessary to increase our ability to successfully detect early season weed infestations.

In-field surveys, which directly estimate weed population densities, typically utilize either random or nonrandom field selection methods. We used both methods to characterize the distribution and frequency of glyphosate-resistant (GR) horseweed populations and other late-season soybean weed escapes and to develop a database for tracking weed shifts, control failures, and the presence of other herbicide-resistant biotypes over time in Indiana. In-field surveys were conducted in a total of 978 Indiana soybean fields during September and October of 2003, 2004, and 2005. Information from fields with horseweed was obtained from 158 sites (19%) sampled through a systematic random site selection method and 128 fields through a nonrandom site selection method. When present, horseweed seed was collected and germinated in the greenhouse; rosettes 5 to 10 cm wide were sprayed with 1.72 kg ae/ha of glyphosate. Populations with less than 60% control at 28 d after treatment were determined to be glyphosate resistant. A selected subset of glyphosate-resistant populations was confirmed resistant by subsequent glyphosate dose response experiments. All populations in the subset with less than 60% control at the 1.72 kg ae/ha rate of glyphosate demonstrated 4- to 110-fold levels of resistance (R : S ratios). Glyphosate-resistant populations were found in all regions of Indiana; however, the highest frequencies were in the southeastern (SE) region with 38% of fields sampled and only 1, 2, and 2% of fields sampled in the northwestern (NW), northeastern (NE), and southwestern (SW) regions, respectively. Information gathered in this survey can assist in the development of applied research, as well as reactive glyphosate-resistant horseweed management education in the SE region of the state. Moreover, detecting resistance at low frequencies can direct proactive resistance education to farmers and practitioners in the other regions of the state as a means of providing an early warning system to address glyphosate resistance in weeds.

Corn and soybean growers across Indiana were surveyed during winter 2003/2004 to assess their perceptions about the importance of glyphosate-resistant weeds and management tactics to prevent development of resistant populations. The survey showed two intriguing observations. First, 65% of survey respondents expressed moderate or low levels of concern about weeds developing resistance to glyphosate, whereas 36% expressed a high level of concern. Second, when asked an open-ended question regarding the factors that contribute to development of glyphosate-resistant weeds, 58% of the responses included repeated use of the same mode of action. Other factors such as poor application techniques or timing (33%), unique weed characteristics (8%) and changes in tillage practices (1%) were also mentioned. The survey showed that even though a relatively low percentage of respondents were highly concerned about resistance, they still expressed a willingness to use field scouting, tank-mix partners with glyphosate for burn-down and postemergence weed control, and soil-applied residual herbicides as resistance management strategies. This survey also showed that growers who farm 800 ha or more were more concerned about glyphosate resistance and more likely to adopt resistance management strategies than smaller growers.

The expansion of populations of invasive species continues to compromise the ecological and economic integrity of our natural resources. The negative effects of invasive species on native biota are widely reported. However, less is known about how the duration (i.e., age of oldest invaders) and intensity (i.e., density and percent cover) of an invasion influences native plant diversity and abundance at the microsite scale. We examined the influence of density, percent cover, and age of Amur honeysuckle (a nonnative invasive shrub), and several environmental factors on native plant taxa at 12 mixed hardwood forests in Indiana, USA. Overall, study sites with the greatest taxonomic diversity (Shannon's Diversity; H′), richness (S), percent cover, and density of native vegetation also had the lowest percent cover of Amur honeysuckle in the upper vertical stratum (1.01 to 5 m). Based on linear mixed model analyses, percent cover of Amur honeysuckle in the upper vertical stratum was consistently and negatively correlated with H′, S, total percent cover, and woody seedling density of native taxa at the microsite scale (P < 0.05). Duration of Amur honeysuckle at the microsite scale was not significant when percent cover of Amur honeysuckle in the upper vertical stratum was included in models. However, duration of Amur honeysuckle invasion was significantly correlated with dependent variables and with upper-stratum honeysuckle cover, suggesting that older Amur honeysuckle in a microsite resulted in greater light competition from above for native understory plant species. Beyond increased cover and shading, our results do not provide evidence of duration-related effects from long-term dominance of honeysuckle in our sampled mixed hardwood forest sites.

Temperate and boreal forests in Canada and the northeastern United States have been invaded by several exotic species, including European earthworms (family Lumbricidae) and garlic mustard. Earthworms and garlic mustard co-occur and are both known to adversely impact some native plant species. However, relatively little is known about potential interactions between these two invaders. In a series of growth chamber experiments, we determined the palatability of garlic mustard and six native herbaceous forest species (shooting star, columbine, wild geranium, sweet cicely, butterfly milkweed, and yellow jewelweed) to the common nightcrawler. We also assessed the ability of the common nightcrawler to bury and digest garlic mustard and wild geranium. When offered seeds from garlic mustard and a native plant species, the earthworms ingested more garlic mustard seeds than seeds from four of the six native species. In a mesocosm experiment, the common nightcrawlers apparently digested 72 and 27% of garlic mustard and wild geranium seeds, respectively, that were placed on the soil surface. No seeds were observed on the soil surface at the end of the experiment but the majority of recovered seeds for both species were found within the top 10 cm (3.94 in). More seeds were recovered in 0- to 10-cm and 31- to 40-cm sections for wild geranium than for garlic mustard. No difference in seed recovery was detected at the other depths. Garlic mustard seed is readily consumed by common nightcrawlers and appears to be preferred over some native plant species suggesting that common nightcrawlers may reduce the size of the garlic mustard seed bank.

Hardwood forests in eastern North America are being colonized by multiple nonnative plant and animal species. Colonization rates can be affected by stand structure and distance from edge. We sampled earthworm densities and understory plant species cover in transects located in paired old- and second-growth forests in Indiana. Two 100-m transects were established within each forest stand during late April to early May in each year. One transect was placed parallel to and within 5 m of a south- or west-facing edge. The second transect was placed parallel to the first. but at no less than 100 m from any edge. Nonnative earthworms and plants were found in forest edge and interior regardless of structural stage (second-growth vs. old-growth). The number of native plant species decreased linearly as the densities of adult Lumbricus and Aporrectodea earthworms and the percent cover of multiflora rose (an invasive plant species) increased. Densities of L. terrestris and Aporrectodea earthworms and percent cover of multiflora rose cumulatively explained 39% of the variation in the number of native plant species found in transects across the state. However, multivariate analyses suggested that the species composition of Indiana understory plant communities was affected more by geography than by earthworm densities. Our results suggest that nonnative earthworms and plants are ubiquitous in Indiana hardwood forests and that they may reduce the number of native plant species.

Glyphosate-resistant (GR) crops have been rapidly adopted in the United States and the evolution of GR weeds throughout the world has also been on the rise. With experience, weed scientists and crop advisers develop “intuition” on the basis of field history and current in-field conditions for predicting whether escaped weed biotypes may be herbicide resistant. However, there are no previous reports on the association of in-field crop management factors with the prediction of herbicide resistance. By using in-field survey data, we tested the accuracy of predicting glyphosate resistance in late-season horseweed escapes. We hypothesized that glyphosate resistance in late-season horseweed populations found in soybean fields could be predicted using in-field knowledge of crop residues and the appearance and distribution of weeds in the field. Field survey data were collected to determine the distribution and frequency of GR horseweed populations in Indiana soybean fields during September and October of 2003, 2004, and 2005. After the in-field survey, soil properties for sampled field locations were also collected from the U.S. Department of Agriculture Natural Resources Conservation Service Web Soil Survey. GR horseweed predictions used in-field presence of crop residues and the appearance, abundance, and distribution of weeds in the field. The significance of independent data factors were determined by chi-square statistics. The interactions and relative significance of multiple factors were modeled using classification and regression tree analysis. Our results indicated that the most important factor for predicting GR populations was the identification of an altered plant phenotype after injury from POST glyphosate. This was followed by crop rotation, field distribution, and the presence of other escaped weed species in the field in a model with a classification rate of 0.68.

Horseweed is an increasingly problematic weed in soybean because of the frequent occurrence of glyphosate-resistant (GR) biotypes. The objective of this study was to determine the influence of crop rotation, winter wheat cover crops (WWCC), residual nonglyphosate herbicides, and preplant herbicide application timing on the population dynamics of GR horseweed and crop yield. A field study was conducted at a site with a moderate infestation of GR horseweed (approximately 1 plant m−2) with crop rotation (soybean–corn or soybean–soybean) as main plots and management systems as subplots. Management systems were evaluated by quantifying horseweed plant density, seedbank density, and crop yield. Crop rotation did not influence in-field horseweed or seedbank densities at any data census timing. Preplant herbicides applied in the spring were more effective at reducing horseweed plant densities than when applied in the previous fall. Spring-applied, residual herbicide systems were the most effective at reducing season long horseweed densities and protecting crop yield because horseweed in this region behaves primarily as a summer annual weed. Horseweed seedbank densities declined rapidly in the soil by an average of 76% for all systems over the first 10 mo before new seed rain. Despite rapid decline in total seedbank density, seed for GR biotypes remained in the seedbank for at least 2 yr. Therefore, to reduce the presence of GR horseweed biotypes in a local no-till weed flora, integrated weed management (IWM) systems should be developed to reduce total horseweed populations based on the knowledge that seed for GR biotypes are as persistent in the seed bank as glyphosate-sensitive (GS) biotypes.

Corn and soybean farmers across Indiana were surveyed in 2003 to determine the perceived importance of weeds at the state and district levels. Weeds were considered the primary crop pest by 69 to 84% of farmers, depending on district. Diseases or insects were ranked first by no more than 14% of farmers and nematodes were ranked first by no more than 11%. Giant ragweed, Canada thistle, common lambsquarters, common cocklebur, and velvetleaf were considered the most problematic summer annual and perennial weeds statewide. Chickweed, horseweed, dandelion, and henbit were considered the most problematic winter annual weeds statewide. However, no weed species was listed by more than 41% of farmers statewide suggesting that relatively unique weed management problems may exist on many farms. Also, the perceived importance of most weed species varied substantially among Indiana's nine districts. For example, velvetleaf was not listed as a problematic weed by any farmers in three districts. Burcucumber was not considered a statewide problem but was listed among the top three weeds by 14 and 16% of farmers in two southern districts. This survey supports the idea that educational programs focused on weed management should be tailored to geographic regions within Indiana.

The development of optimal weed management strategies that rely, in part, on crop interference will require an understanding of how weeds compensate for limitations in above- and belowground resources. Trade-offs in the leaf morphology and biomass partitioning of rice and late watergrass were investigated under glasshouse conditions in 1999 and 2000. Both species responded to shade with increased height, reduced biomass, greater partitioning of biomass to leaves, and greater leaf area ratios. At the lowest light level (18% sunlight), plants of both species showed little response to nitrogen (N). However, height, tillers, biomass, and leaf area increased for plants grown at 50% and full sunlight as N increased from 0 to 224 kg N ha−1. Late watergrass exhibited more plasticity in specific leaf area and root weight ratio than rice in response to shade. This plasticity contributed to the ability of late watergrass to maintain a higher percent of its tillers and total dry weight than rice when sunlight was reduced by 50%. These results support the hypothesis that except at low light levels, limited N further reduces the growth of shaded late watergrass plants. Thus, weed management strategies that limit the plasticity of late watergrass by manipulating light and N availability are likely to be more effective than strategies that rely on manipulating a single resource.

In 2006, the Midwest Invasive Plant Network's Research Committee conducted a web-based survey to help identify research needs and interactions between land managers and researchers working to manage invasive plants in the Midwest. Of 192 responses, 30% identified themselves as researchers and 70% identified themselves as managers. Researchers and managers rated working together on invasive plant issues as high or medium in importance, but neither group rated the current level of cooperation as high, with over 90% describing current cooperation as low or medium. Both groups self-associate, with 89% of researchers working with other researchers and 77% of managers working with other managers. “Lack of time” and “lack of money” were the main issues limiting researchers and land managers from working more closely together: money was a greater constraint for researchers and time was more important for land managers. To help researchers and land managers work more effectively together, both groups favored opportunities to develop research-based projects at land managers' sites, with funding from a cooperative grant program. Open-ended responses suggest that on-site experiments and demonstrations of management methods could help researchers and land managers interact more effectively. Researchers rated basic biology as more important than land managers did, but neither group judged testing theories of invasion as a high priority. “Social/political factors” and “risk assessment” were viewed as less important despite their clear relevance in the introduction and spread of invasive plants.

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.

Weeds that emerge between rows in fresh market tomatoes after the critical period of competition are not suppressed by the crop and can produce large quantities of seed. A living mulch planted between rows might limit weed seed production. Buckwheat was seeded between tomato rows after the critical period in 2007 and 2008 in field studies near Lafayette, IN. Weeds were allowed to emerge after the critical period (CP), controlled throughout the growing season (no seed threshold [NST]), or mowed to limit seed production (MOW). Buckwheat and MOW plots were mowed twice after the critical period in 2007 and once in 2008. Seed banks were sampled after the critical period and in the following spring. Tomato yields were not reduced by growing buckwheat between rows. Seed bank densities for common purslane and carpetweed, which escaped mowing due to their prostrate habits, increased in all treatments. Germinable seed bank densities were 306 seeds m−2 or less in the NST and buckwheat treatments but 755 seeds m−2 or more in the CP treatments for species with erect habits in both years. Seed bank densities were lower in the MOW treatment than in the CP treatments in 2007 but not in 2008. In a parallel experiment conducted in adjacent plots, buckwheat was seeded at five rates (0, 56, 112, 168, and 224 kg seed ha−1). Plots were mowed and emergent weeds sampled as described for the intercrop experiment. Weed densities before mowing decreased linearly with buckwheat seed rate. After mowing, no relationship was detected between seed rate and weed densities. This study supports the hypothesis that a living mulch planted after the critical period can be used to limit seed bank growth without reducing tomato yields, but additional research is needed to better understand the effect of mowing on living mulch growth and weed suppression.

Weed control strategies based on conserving crop yields rather than preventing weed seed production may result in increased weed densities and management costs over the long-term, particularly in less competitive crops such as tomatoes. The effect of crop, tillage, and duration of weed control on weed seed bank size and composition was examined from spring 2001 to spring 2003 near Lafayette, IN. Main plots in 2001 and 2002 contained soybean or tomato planted in rotation (soybean-tomato, tomato-soybean). Subplots were managed with either conventional or no-till practices. Sub-subplots contrasted threshold strategies in which weeds were either controlled for four to six weeks (period threshold, PT) or throughout the growing season (no-seed-threshold, NST). Seed banks were sampled annually in the spring. Emergent weeds were counted` at four and twelve weeks after planting (WAP) in 2001 and 2002. Weed seed banks did not significantly change in the NST plots in any year. However, seed bank densities increased substantially following tomatoes in PT plots. In contrast, weed seed bank densities decreased following soybeans in PT plots. The difference in seed banks and emergent weeds between soybean and tomatoes could be attributed primarily to greater suppression of giant foxtail by the soybean canopy. Giant foxtail control was greater in PT soybeans than in PT tomatoes in both years and giant foxtail comprised most of the PT tomato seed bank in 2002 and 2003. Tillage did not affect weed seed banks in any year. This study highlights the need to control later emerging weeds in tomatoes to prevent large increases in the weed seed bank.

Horseweed is an increasingly common and problematic weed in no-till soybean production in the eastern cornbelt due to the frequent occurrence of biotypes resistant to glyphosate. The objective of this study was to determine the influence of crop rotation, winter wheat cover crops (WWCC), residual non-glyphosate herbicides, and preplant application timing on the population dynamics of glyphosate-resistant (GR) horseweed and crop yield. A field study was conducted from 2003 to 2007 in a no-till field located at a site that contained a moderate infestation of GR horseweed (approximately 1 plant m−2). The experiment was a split-plot design with crop rotation (soybean–corn or soybean–soybean) as main plots and management systems as subplots. Management systems were evaluated by quantifying in-field horseweed plant density, seedbank density, and crop yield. Horseweed densities were collected at the time of postemergence applications, 1 mo after postemergence (MAP) applications, and at the time of crop harvest or 4 MAP. Viable seedbank densities were also evaluated from soil samples collected in the fall following seed rain. Soybean–corn crop rotation reduced in-field and seedbank horseweed densities vs. continuous soybean in the third and fourth yr of this experiment. Preplant herbicides applied in the spring were more effective at reducing horseweed plant densities than when applied in the previous fall. Spring-applied, residual herbicide systems were the most effective at reducing season-long in-field horseweed densities and protecting crop yields since the growth habit of horseweed in this region is primarily as a summer annual. Management systems also influenced the GR and glyphosate-susceptible (GS) biotype population structure after 4 yr of management. The most dramatic shift was from the initial GR : GS ratio of 3 : 1 to a ratio of 1 : 6 after 4 yr of residual preplant herbicide use followed by non-glyphosate postemergence herbicides.

Biochar, a carbon-rich product formed by the incomplete combustion of biomass, has been shown to improve soil quality and increase crop growth but has not been evaluated in prairie ecosystems. We assessed the response of a native perennial grass, big bluestem, and an invasive herbaceous perennial, sericea, to biochar amendments in two greenhouse experiments in 2010 and 2011. In the first experiment, big bluestem and sericea were grown in monoculture; the main treatments were soil type (silt, sand), percent biochar (0%, 1%, 2%, and 4%) and nitrogen (0 and 10 g N m−2). Big bluestem growth was increased by the addition of biochar, particularly in the sand soil. In contrast, sericea growth was either not affected or decreased when biochar was added to the soil, particularly at the higher biochar rates. Adding N to the soil appeared to increase sericea growth in the presence of biochar and the silt soil, which suggests that biochar may have reduced N availability. A replacement series was used in the second experiment to evaluate the effect of biochar on competition between the two species. Main treatments were biochar rates (0% and 2%), nitrogen rates (0 and 10 g N m−2) and the following big bluestem to sericea ratios: 6 : 0, 4 : 2, 3 : 3, 2 : 4, and 0 : 6. After 180 d, big bluestem height and biomass were significantly greater in biochar-amended soils than in unamended soils. However, sericea height and biomass were unaffected by biochar amendments and the addition of biochar did not alter competitive outcomes. Competition between big bluestem and sericea was asymmetrical; sericea reduced the growth of big bluestem but big bluestem had relatively little effect on the growth of sericea. Our research suggests that biochar has the potential to increase the growth of big bluestem and may be a useful tool for prairie restoration.