Winter camelina [Camelina sativa (L.) Crantz] and pennycress (Thlaspi arvense L.) are gaining commercial traction as "intermediate" oilseed feedstocks for sustainable aviation fuel in the US. Relay cropping soybean [Glycine max (L.) Merr.] with pennycress or camelina can greatly increase oil yield per hectare. However, relayed soybean yields can significantly lag those of full-season monocrop soybean. Better understanding of the limitations of soybean growth and development under this relay system is needed. Over two growing seasons (2014-2016) in west central Minnesota, leaf photosynthesis and growth were evaluated for relay cropped soybean following winter oilseed harvest and compared with a monocrop soybean control. Leaf area index (LAI) of the winter oilseeds was measured during their overlap phases with relayed soybean, and crop water use (WU) was estimated in all treatments between early spring and winter oilseed harvest. Pennycress LAI was greater than camelina during the overlap phase. After pennycress harvest, relay crop soybean photosynthesis averaged 52% less than the monocrop control but was only 28% less after camelina harvest. Photosynthesis of soybean relayed into camelina also recovered sooner than soybean relayed into pennycress. Crop WU did not differ among treatments. Averaged over both growing seasons, yield of soybean relayed in winter camelina was 18% greater than that relayed in pennycress, but both were significantly lower than the monocrop control. Managing the relay system to allow more light penetration to soybean (e.g., modifying plant and row spacing) and/or selecting more shade tolerant soybean genotypes might help to improve relayed soybean yields.

Pennycress is being developed in the Midwestern USA as a new oilseed crop that provides numerous ecosystem services. These services include being an early spring source of pollen and nectar for flower-visiting insects. Most past research on pennycress flower visitors used wild genotypes of pennycress. All wild genotypes have seed coats that are black, which occurs because of high levels of proanthocyanadins (PACs). Concentrations of PACs are minimal in newly developed genotypes with yellow-colored seed coats. However, little is known regarding flower abundance and timing nor insect visitation preferences for black-seeded genotypes (BSG) or yellow-seeded genotypes (YSG) of pennycress. Flower densities were recorded and pan traps were deployed weekly during pennycress flowering at nine site-years in Illinois and Minnesota to examine anthesis and insect preferences for BSG vs. YSG pennycress. BSG and YSG flowered simultaneously, responded similarly to post-sowing growing degree days (peaking at 700 GDD4°C), and produced comparable numbers of open flowers (up to 10,000 m-2) on any given day, although BSG produced significantly greater numbers of cumulative flowers over the course of anthesis in three of nine site-years. Overall, the percentages of all trapped insects comprised of differing taxonomic orders were as follows: Diptera (flies) 33-37%, Thysanoptera (thrips) 27-30%, Hymenoptera (bees and wasps) 13-20%, Hemiptera (true bugs) 7-8%, Coleoptera (beetles) 5-6%, and Lepidoptera (butterflies and moths) 1-3%. Generally, there were no significant differences in the relative abundance of insects found in YSG versus BSG pennycress across site-years. Occasionally, however, pan traps in BSG pennycress contained more insects, which mainly was due to high Dipteran populations. These results suggest that genetic selections for yellow seed coats (with low PACs) will have little impact on flower abundance and attractiveness to most insect visitors.

Although many insects are known to be associated with the floral canopies of oilseed pennycress (Thlaspi arvense), those that carry the crop’s pollen are unknown. During early spring of 2024 insects associated with pennycress flowers in Illinois and Minnesota were captured in sweep nets, frozen, sorted by species, and sonicated to remove pollen. Pollen grains were counted, and pollen loads per individual insect were calculated. Members of the orders Diptera, Hemiptera, and Hymenoptera accounted for 66%, 16%, and 14% of the 850 insects examined, but these same orders were responsible, respectively, for 18%, 3%, and 78% of the total pollen load of nearly a quarter of a million pollen grains. Insects carrying > 1000 pollen grains per adult included the bees Apis mellifera (Apidae), Andrena cressonii (Andrenidae), Halictus confusus, H. rubicundus, and Lasioglossum pruinosum (Halictidae); as well as the flies Dolichopus sp. (Dolichopodidae), Eristalis tenax and Eupeodes americanus (Syrphidae). Additionally, several insect species carried modest pollen loads (50-500 grains per individual), including parasitoids (e.g., Diadegma insulare, Hymenoptera: Ichneumonidae), predators (e.g., Toxomerus marginatus, Diptera: Syrphidae), as well as crop pests (e.g., Delia platura, Diptera: Anthomyiidae). This suggests that the flowering canopy of pennycress is a diverse floral ecosystem with many potential insect pollinators and an array of associated ecological interactions.

The production of organic meat and dairy products relies on limited organic protein meal supplies. Camelina (Camelina sativa L.) may sustainably increase organic protein meal supplies. Using grain production trial data, research literature, and camelina feeding trial results, greenhouse gas (GHG) emissions and fossil energy impacts were modeled for inclusion of 10% camelina meal in swine finishing diets using life cycle analysis (LCA). Two key grain production scenarios were examined: field trial relay (FTR) camelina and a higher yielding as expected relay (AER) camelina, with a baseline monocrop soybean (MCS). At the grain production stage, the FTR, AER, and MCS scenarios emitted 0.65, 0.43, and 0.13 kg of CO2 eq./kg DM grain harvested, respectively. At the meal production stage, 0.61, 0.40, and 0.15 kg of CO2 eq. were emitted per kg of protein meal from the FTR, AER, and MCS scenarios, respectively. GHG emissions from the finishing phase of pork production were 1.43, 1.38, and 1.31 kg CO2 eq./kg live weight pigs produced for the FTR, AER, and MCS scenarios, respectively. Findings were similar for fossil energy use. The higher environmental burdens from camelina grain production due to reduced yields of both camelina and soybean resulted in negative environmental performance in camelina-amended diets.

Declining natural pollinator populations are a potential threat to global food supplies. Mass flowering summer annual oilseeds can provide much needed crop diversity and floral resources to support pollinator communities. We evaluated how managing planting date affects floral phenology, floral accumulation (flower coverage time x flower area), pollinator visitation, pollinator diversity and yield of nine oilseed crops. Borage (Borago officinalis L.), calendula (Calendula officinalis L.), crambe (Crambe abyssinica Hochst), cuphea (Cuphea viscosissima Jacq. x Cuphea lanceolata W. T. Aiton), echium (Echium plantagineum L.), flax (Linum usitatissimum L.), spring camelina (Camelina sativa (L.) Crantz), spring canola (Brassica napus L.) and sunflower [Helianthus annuus L.] were grown in Morris, Minnesota during the summers of 2013 and 2014. Each crop was planted on a "standard" planting date of mid-May and additional planting dates of early May, early June and early July. Shifting planting dates affected flowering phenology, floral accumulation, pollinator visitation and crop yield. Later planting dates led to later onset of flowering for all crops and affected total floral accumulation for crambe, cuphea and echium. Pollinator visitations changed with planting date and were generally greater with the later planting dates. At least two of the four planting dates supported high yield for each crop. The ability to maintain high crop yield across a window of planting dates affords growers management options for their fields and can be used to design complementary resource pairing and improve pollinator health through crop diversification and management.

In the Upper Midwest, corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] are the most prominent agricultural crops, occupying land for only half the year. Their fallow periods are associated with nutrient leaching and soil erosion, but they also represent an opportunity to establish winter-hardy crops, like pennycress (Thlaspi arvense L.), that can reduce negative environmental impacts while contributing to farm profitability. A lack of agronomic best management practices remains a barrier to pennycress adoption. The objectives of this study were to evaluate the impact of stover presence on pennycress stand establishment and seed yield after seeding pennycress into R4 corn. This study was conducted over the 2014-2015 and 2015-2016 growing seasons with MN106 pennycress at three locations in Minnesota. At maturity, corn plants were removed from plots in 25% increments between 0% and 100% to simulate stover removal scenarios. Pennycress seedlings were unable to compete with corn for available light resources and did not have enough time following corn harvest to establish a dense stand in the autumn with only 5% and 10% green cover in 2014 and 2015, respectively. Despite poor early season emergence, the average seed yield, 1223 kg ha-1, was high relative to other studies using MN106, indicating that challenges of growing pennycress under adverse conditions may not be a barrier to competitive seed yields. Experimentation on the corn-pennycress system should continue in the future to further explore and establish best management practices for this double crop. Rate of stover removal minimally impacted pennycress germination. Pennycress seedlings provided little autumn soil coverage. Stover removal rate did not affect pennycress seed yield.

Flies are frequent visitors to flowers of many species of plants within the mustard family (Brassicaceae). They derive nutrition from these flowers, and some fly species are pollinators. Field pennycress (Thlaspi arvense) is a mustard species that is being developed as a new "cash cover crop," i.e., an autumn-sown cover crop whose oil-rich seeds can be harvested profitably in spring. Although pennycress is largely wind- and self-pollinated, its flowers also attract insect visitors. However, the extent of visitation to pennycress flowers by flies remains largely unknown, especially the identities of those flies. Thus, we examined flies associated with pennycress flowering canopies at five site-years in Illinois and Minnesota. The number of fly species averaged 16 per site-year. Hover flies (Syrphidae) were common visitors to pennycress flowering canopies, representing 24% of all Diptera collected. Toxomerus marginatus (margined calligrapher), whose larvae are aphid predators, was especially abundant within this family. However, the most common flies detected were Delia spp. (Anthomyiidae, root maggot flies), which averaged 51% of all flies collected. Adults of these flies are known pollinators, but their larvae also are pests that can damage seedlings of common summer crops. Although seedling damage to plants that are double- or relay-cropped (i.e., inter-seeded in spring) with pennycress has not been observed yet, close observation of this insect group and its effects may be needed if pennycress is widely sown in the future as a cash cover crop.

Abstract Two sequential experiments examined the effects of abrasive grit on seedlings of grass weeds and young shoots of perennial weeds. First, four types of grit derived from agricultural residues (bone meal, eggshell, hazelnut shell, and sugar beet pulp) were tested under high air pressure in a controlled environment for their abilities to abrade seedlings of an annual grass, Setaria faberi Herrm., and the perennials Festuca arundinacea Schreb., Poa pratensis L., and Elymus repens (L.) Gould. Differing grit particle sizes and amounts, as well as weed seedling stages, were examined for efficacy after abrasion by each type of grit. Second, hazelnut shell grit was used to control P. pratensis and Taraxicum officinale Weber in field trials with aronia (Aronia melanocarpa [Michx.] Elliott), which is a new, shrubby, berry crop in the midwestern USA. Grit weeding was compared to two other treatments: manual weeding (hand-hoeing + hand-pulling) and no weed control (weedy check) over two years. In the grit comparison experiment, control of S. faberi was highest for egg-shell grit (63–100% across grit particle sizes, rates, and seedling stages) and least for sugar beet pulp (17–97%). The former grit had the highest bulk density of all grits, and the latter had the lowest bulk density. For damage to perennial weeds, egg-shell grit performed best (17–80% control) and bone meal least (10–47% control). Elymus repens was controlled better than other perennial grasses, especially by eggshell grit (up to 73% control) and hazelnut shell grit (up to 67% control) with particle sizes of 1–2 mm. In the aronia experiment, both grit abrasion and manual weeding achieved comparable levels of weed suppression (≥87%) and required similar amounts of cumulative seasonal time spent weeding (3–4 min per shrub). Thus, applications of abrasive grit derived from agricultural residues are potential alternatives for non-chemical management of weeds in aronia and, perhaps, in other high-value perennial crops.

New forms of weed control may be useful in apple orchards. Abrasive corn cob grit applied under high air pressure was tested for the control of weeds in an established apple orchard over two years. Additionally, efficacy of abrasive grit-weeding was compared to that of hand-weeding. As expected, hand-weeding nearly eliminated all weeds. In contrast, grit-weeding achieved about 90% control of broadleaf weeds, only 15% control of grass weeds, and 70 to 80% control of all weeds. Much of the time and amount of grit used was devoted to suppressing grass weeds. Relatively soft corn cob grit easily abraded and controlled broadleaf weeds. However, harder and more angular grit materials may be needed to control annual and perennial grasses.

Oilseed pennycress (Thlaspi arvense) is a new, autumn-sown, “cash cover crop” for the Midwestern USA and elsewhere. Anthesis occurs in early spring when few other plants bloom, and its flowers attract early-emerging bees. However, the taxonomic composition of these bees was unknown. Consequently, we systematically captured and identified the genera and species of bees visiting pennycress flowers throughout anthesis at five site-years: two in Illinois and three in Minnesota. A cumulative total of 28 bee species were found across site-years. The most common genera were Andrena (10 species), Lasioglossum (12 species), and Halictus (2 species). Rarer genera were Apis, Ceratina, Hylaeus, and Nomada. Bee abundance and diversity were related closely and in a negative exponential manner with percent land area devoted to annual cropping. The inclusion of new early flowering crops, such as pennycress, may enhance bee abundance and diversity, especially if even small areas of uncropped land are nearby.

In the Upper Midwest, corn (Zea mays L.) and soybean (Glycine max [L.] Merr.) dominate the landscape, but only for six to seven months of the year. Thus, opportunities exist to establish crops that can utilize the remainder of the growing season and contribute to overall farm profitability. One species of interest is pennycress (Thlaspi arvense L.), but a lack of established agronomic best management practices is a barrier to successful crop production. The objectives of this study were to identify a range of cumulative growing degree days (CGDD) corresponding to pennycress physiological maturity, determine the optimal harvest window that maximizes pennycress seed yield and oil content, and characterize changes in pennycress seed attributes over seed maturation. This study was conducted over the 2016-2017 and 2017-2018 growing seasons with 'MN106' pennycress at two locations in Minnesota, USA. Seed dry weight stabilized within the window of maximum seed yield, but oil content did not maximize until after this period. However, there was minimal loss of oil content when pennycress was harvested within the seed yield maximization window. Based on these parameters, as well as seed moisture, it was estimated that pennycress reached physiological maturity between 2230 and 2250 degrees C d CGDD, or about a week prior to harvest maturity in terms of crop phenology. Delaying harvest to harvest maturity resulted in a 26% loss in harvestable seed due to seed shatter compared with the average maximum seed yield of 928 kg ha-1. Ensuring maximum pennycress seed yield and oil content at harvest is imperative to successful production and contribution to farm economic viability.

Objective: We investigated whether increasing inclu-sion of camelina press cake (CPC) in pig diets would influ-ence carcass traits, pork quality, and belly firmness. Materials and Methods: Pigs (initial weight = 35.3 +/- 2.8 kg) were fed diets based on corn-soybean meal with 0, 5, 10, or 15% CPC to replace corn and soybean meal for 12 wk. There were 6 pens of 8 pigs each per dietary treat-ment. At 23 wk of age, gilts (n = 22), each from a different pen, were slaughtered for pork quality evaluation. Data were analyzed using the Glimmix models of SAS. Results and Discussion: Increasing dietary inclusion of CPC decreased (P < 0.05) hot carcass weight, dressing percentage (DP), belly thickness, and backfat thickness at the 10th rib, and increased lean percentage of carcasses. Changes in chill loss percentage, 45-min and 24-h post -mortem pH, water holding capacity and marbling score of pork chops, or belly firmness with increasing CPC inclu-sion were not detected (all P > 0.10). Increasing CPC in-clusion decreased (P < 0.05) Warner-Bratzler shear force value and objective color (a*) of pork chops quadratically. Subjective color and overall appearance scores across 7 d were less favorable (P < 0.05) for pork chops from pigs fed increasing dietary inclusion of CPC to 15%. But, changes in shear force value, subjective color, and overall appear-ance scores for pork chops with dietary CPC inclusion were of small magnitude. Implications and Applications: Increasing dietary inclusion of CPC up to 15% decreased hot carcass weight, DP, and belly thickness but increased lean percentage of carcasses.

Flowers of field pennycress (Thlaspi arvsense L.) and winter camelina (Camelina sativa (L.) Crantz.) produce abundant pollen and nectar in early spring and thereby may be valuable for pollinators. Insects observed in field plots of these flowers were classified into seven easily identifiable groups (bumblebee, honeybee, solitary bee, butterfly/moth, beetle, fly and other) and monitored for 2 years at three sites in the Upper Midwest region of the USA. Average seasonal observations across years and sites varied from 1.6 to 5.3 total insects/min for field pennycress and 1.4 to 4.5 insects/min for winter camelina. Lowest visitation rates occurred in central Iowa and highest rates in south‐eastern Minnesota for both crops. Multiple regressions showed that visitation rates for specific insect groups were correlated poorly but significantly (p < .10) with select variables. For example, in field pennycress, visitation by combined bumblebees and honeybees (Apidae) increased with greater air temperature at sampling time and annual site precipitation, whereas fly (Diptera) visitation was related to sampling date and flower cover. Similarly, in winter camelina, solitary bees were linked to increasing air temperature at sampling time and annual site precipitation, whereas flies were correlated with wind speed and flower cover at sampling. Field pennycress and winter camelina are reliably attractive to beneficial pollinating insects across a wide geographic region, but visitation rates and proportional representation of various insect groups depended on a range of site and weather characteristics.

The objective of this experiment was to determine the dietary inclusion rate of camelina cake (CC) that would support the growth performance of growing-finishing pigs similar to that of a corn-soybean meal-based diet. Pigs (n = 192; BW = 35.2 kg; Duroc x (Yorkshire x Landrace)), balanced for sex and initial weight, were assigned to pens (8 pigs/pen) and pens were assigned randomly to one of four dietary treatments (6 pens/treatment). Treatments consisted of a non GMO corn-soybean meal control diet (CON), or CON containing 5% (5CC), 10% (10CC), or 15% (15CC) camelina cake. Feed disappearance on a pen basis and individual body weights of pigs were recorded every other week to calculate average daily gain (ADG), average daily feed intake (ADFI), and gain to feed ratio (G:F) on a pen basis. Prior to harvest, real-time ultrasonic measurements of back fat depth and loin eye area were collected on all live pigs. Pigs were harvested as a single group at about 23 weeks of age at a commercial abattoir. Data were analyzed using Proc Glimmix with dietary treatment as a fixed effect and pen serving as the experimental unit. Growth performance data collected over time were analyzed using repeated measures within the Proc Glimmix procedure. Overall, pigs fed CON exhibited similar ADG to those consuming 5CC and higher ADG than pigs consuming 10CC and 15CC diets (1.10 kg vs. 1.05 kg for 10CC and 1.02 kg for 15CC; P < 0.05 for both mean comparisons). Pigs fed CON consumed more feed than pigs fed any of the CC diets (ADFI = 2.66 kg for CON vs. 2.46 kg for 5CC, 2.46 kg for 10CC and 2.47 kg for 15CC; P < 0.05 for all). These differences resulted in heavier (P < 0.05) CON-fed pigs at marketing than 10CC or 15CC-fed pigs. There were no differences in any carcass traits analyzed. From these data, we conclude that feeding up to 5% CC in corn-soybean meal-based diets did not negatively influence growth performance, or carcass traits of growing-finishing pigs.

The sustainability of organic production and cover crops depends on production costs and the economic value of products. Feed cost, contributing 65–75% of the total production cost, has a significant impact on profitability of organic pig farming. Utilizing grains harvested from cover crops as a feed ingredient for organic pigs can potentially protect the environment and increase the economic value of cover crops. This study was the first to evaluate the viability of integrating winter cover crop, camelina, into organic pig production. Winter camelina was grown organically in single or relay with soybeans to increase the total yield per hectare. Camelina yields in monocrop and in relay-crop fields were 1,394 and 684 kg ha −1 , respectively. Although the total yield of camelina and soybean (1,894 kg ha −1 ) in the relay-crop field was higher than camelina yield in the monocrop field, monocropping camelina is more economical than relay-planting with soybeans due to the difference in production costs. Camelina press-cake was supplemented in diets fed to pigs raised under near-organic standards. Supplementing 10% camelina press-cake in diets reduced feed intake, weight gain, final weight at market, carcass weight, and dressing percent of pigs, but did not affect feed efficiency, belly firmness or pork quality. The viability of integrating camelina into organic pig production depends on marketing organic pigs for $2.4 kg −1 of live weight and marketing camelina oil for $3.59 kg −1 or more if monocropping.

Abrasive weeding is a nonchemical weed control tactic that uses small, gritty materials propelled with compressed air to destroy weed seedlings. Organic fertilizers have been used successfully as abrasive grits to control weeds, but the goal for this study was to explore the effects of fertilizer grit, application rates, and background soil fertility on weeds, plant available nitrogen (N) uptake, and crop yield. Field trials were conducted in organic ‘Carmen’ sweet red pepper (Capsicum annuum) and organic ‘Gypsy’ broccoli (Brassica oleracea var. italica) and treatments included organic fertilizer grit (8N–0.9P–3.3K vs. 3N–3.1P–3.3K), grit application rates (low vs. high), compost amendments (with and without), and weedy and weed-free controls. Weed biomass was harvested at 84 days and 65 days after transplanting for pepper and broccoli, respectively. Simulated total plant available N (nitrate + ammonium) uptake was measured with ion exchange resin stakes between 7 and 49 days after the first of two grit applications. Produce was harvested at maturity, graded for marketability, and weighed. The higher grit application rate, regardless of fertilizer type, reduced the weed biomass by 75% to 89% for pepper and by 86% to 99% for broccoli. By 5 weeks after the first grit application, simulated plant N uptake was greatest following grit application with the 8% N fertilizer, followed by the 3% N fertilizer, and lowest in the weedy control. The high grit application rate of 8% N fertilizer increased pepper yield by 112% compared with the weedy control, but it was similar to that of the weed-free control. Broccoli was less responsive to abrasive grits, with yield changes ranging from no difference to up to a 36% increase (relative to the weedy control) depending on the application rate and compost amendment. This is the first evidence indicating that the nutrient composition of organic fertilizer abrasive grits can influence in-season soil N dynamics, weed competition, and crop yield. The results suggest that abrasive weeding technology could be leveraged to improve the precision of in-season fertilizer management of organic crops.

Locally grown strawberries are a high value crop, and the potential for a longer production season is possible with day-neutral cultivars. Weed control is ranked as a top concern for specialty crop farmers in the northern US. During 2019, we conducted a trial to determine if cover crops controlled weeds between rows as effectively as landscape fabric. We planted two strawberry cultivars, 'Albion' and 'Cabrillo', with four between-row treatments at West Central Research and Outreach Center (WCROC), and an observational trial at Twin Cities Berry Company (TCBC). The four between-row treatments included winter canola (Brassica napus 'Torrington'), winter camelina (Camelina sativa 'Joelle'), winter ryegrass (Secale cereale 'Ryman'), and landscape fabric. There were significant differences in yield among between-row treatments. Yield was equivalent between fabric and annual ryegrass. Canola produced significantly lower yield plant-1 than either fabric or rye. There was no significant interaction with cultivar and between-row treatment, concluding between-row treatments operated similarly across cultivars. 'Cabrillo' had a higher average yield plant-1 than 'Albion' regardless of between-row treatment. Our farmer-collaborator concluded he will continue using fabric on a commercial scale due to reduced time inputs for weed control compared with cover crops.

Relay-cropping of the novel oilseeds winter camelina (Camelina sativa L.) and pennycress (Thlaspi arvense L.) with short-season crops such as soybean [Glycine max (L.) Merr.] can provide economic and environmental incentives for adopting winter cover crop practices in the U.S. Upper Midwest. However, their ability to reduce nutrient loss in surface runoff is unknown. Accordingly, surface runoff and quality were evaluated during three seasonal phases (cover, intercrop, and soybean) over 2 yr in four cover crop-soybean treatments (pennycress, winter camelina, forage radish [Raphanus sativus L.], and winter rye [Secale cereale L.]) compared with no-till and chisel-till fallow treatments. Runoff was collected with Gerlach troughs and assessed for concentrations and loads of NO3 - -N, total mineral N, soluble reactive P (SRP), and total suspended solids (TSS). Cumulative runoff and nutrient loads were greater during the winter cover phase because of increased snow melt and freeze-thaw released nutrients from living vegetation. In contrast, cumulative TSS was greater during intercrop and soybean phases due to high-intensity rainfall events with an open soybean canopy. Average TSS loads during the intercrop phase were reduced by 75% in pennycress compared with fallow and radish treatments. During the soybean phase, average TSS, total mineral N, and SRP loads were generally elevated in cover crop treatments compared with no-till. Overwintering cover crops may contribute to mobility of nutrients solubilized from living or decomposing vegetation; however, this was balanced by their potential to reduce runoff and TSS during high-intensity spring rains.

Weed competition, especially within the crop row, limits the productivity and profitability of organic crop production. Abrasive weeding, a mechanical alternative to hand weeding, uses air-propelled grits to control small weed seedlings growing within the crop row. Recent research has demonstrated the successful use of abrasive weeding to reduce weed competition and increase yields in organic maize (Zea mays), tomato (Solanum lycopersicum) and green and red pepper crops (Capsicum annuum), but the profitability of this weed control tactic has not been assessed. Our objective was to determine the profitability of abrasive weeding using empirical yield data from three previously published studies, a range of crop prices and revenues, and a range of costs for wages, grit applicator ownership, tractor use, abrasive grits, and fuel. Results suggest that abrasive weeding was not profitable in organic maize production, and may reduce net income by US$223-3537 ha(-1)compared with inter-row cultivation alone for weed control. The cost of abrasive weeding in maize was largely dependent on the cost of abrasive grits and the cost to own a four-row grit applicator (US$736-2105 yr(-1)). However, abrasive weeding was less expensive than hand weeding, especially as the scale of production increased. Abrasive weeding was profitable in tomato and pepper crops and increased net mean income by US$12,251-33,265 ha(-1). However, abrasive weeding was not 100% effective and hand weeding for weed-free conditions was always the most profitable approach to in-row weed management in vegetable crops. The profit potential of the hand-weeded, weed-free treatments demonstrates the importance of weed control in high-value specialty crops-even those grown in plastic mulch film. Despite the profit potential for hand weeding observed here, labor is increasingly difficult to source, retain and afford, and abrasive weeding offers a mechanical alternative with 66% less labor required. Further research is needed to improve the efficacy of abrasive weeding and to reduce the cost of abrasive grits and application.

Growers desire more techniques to control weeds in horticultural crops that are grown organically and consumed directly, such as red raspberry. Abrasive grit emited via high air pressure is a new method for controlling weeds. Grit derived from corn cobs was examined for its efficacy during the year of raspberry establishment for 2 to 3 years at three sites (seven site-years) and compared with efficacy of hand-weeding as well as no weed control. Grit was applied once or twice weekly after raspberry transplantation in spring until weed emergence ceased in mid to late July. Weeds and raspberry growth were assessed in August. Grit was effective in controlling broadleaf weeds, averaging 94% control across site-years, but control of grass weeds was less than 10%. Total weed (broadleaf plus grass) control across site-years ranged from 51% to 96% and averaged 78%. Raspberry cane growth was affected by weeds, and grit-weeding at least partially alleviated these effects. Thus, abrasive grit allows growers to manage broadleaf weeds effectively without herbicides or soil tillage. However, additional research is needed to determine the correct amounts and timing of grit applications, as well as more efficacious types of grit, to control grass weeds.