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  • Author or Editor: Sam E. Wortman x
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Grafted tomato (Solanum lycopersicum) production is popular, particularly in high tunnels, because grafted plants can mitigate soilborne disease incidence in highly infested soils and increase water and nutrient use efficiency and crop yield and quality. However, these potential benefits are not as well documented in open field production systems with less disease pressure. The objective of this study was to quantify the effect of tomato grafting on fruit yield, number, and size across 2 years (2018 and 2019) and three diverse open-field production environments in Nebraska (Lincoln, North Platte, and Dwight). At each location, a scion from one of two determinant fresh market tomatoes, ‘Nebraska Wedding’ (heirloom) or ‘BHN 589’ (commercial hybrid), were grafted onto one of two rootstocks, ‘Estamino’ and ‘Maxifort,’ and the nongrafted scion cultivars were controls. In year 2, a fertilizer treatment was introduced (0 and 50 kg·ha−1 N). Ripe tomatoes were harvested weekly, sorted as marketable or cull, counted, and weighed fresh. No marketable or total yield benefits of grafting were observed in 2018 for any scion by rootstock combination across locations. Marketable yield of grafted plants was reduced by 32% in Lincoln. However, grafted ‘Nebraska Wedding’ plants (regardless of rootstock) in North Platte (with coarse-textured, lower organic matter soil) increased fruit number (but not yield) by 50% to 63%. In 2019, grafting ‘BHN 589’ to ‘Maxifort’ increased total tomato yield by 24% across all locations. The heirloom variety Nebraska Wedding did not benefit from grafting in 2019. ‘Estamino’ rootstock did not increase tomato yield, number, or size for either scion variety in either year. Nitrogen fertilizer increased yield as expected in 2019, but grafted plants did not perform better than nongrafted under reduced nitrogen fertility. Results from this study suggest that grafting is not consistently beneficial to ‘BHN 589’ and ‘Nebraska Wedding’ in open field production systems in Nebraska, particularly if there are no known soilborne disease issues.

Open Access

Polyethylene mulch use is common in vegetable production, but disposal of mulch is problematic for growers and of significant environmental concern. Biodegradable fabrics and plastic films are compostable and can be incorporated into the soil at the end of the growing season, but questions remain about the durability, performance, and rate of decomposition of these products after soil incorporation. Three trials were conducted in field and high tunnel cucumber (Cucumis sativus) cropping systems to compare performance and decomposition after use among two bioplastic films and four experimental spunbond, nonwoven biofabrics. Soil temperature and moisture, mulch durability and deterioration, weed suppression, and crop yield data were collected in each growing season. All biomulches were soil incorporated after the growing season and recovered up to 11 months after incorporation to estimate relative rates of decomposition. One bioplastic film increased field soil temperature by 2 °C in 2013, but temperatures under the biofabrics were not different from bare soil. Bioplastics and biofabrics increased soil moisture relative to bare soil. Bioplastic films were less durable and deteriorated sooner than biofabrics, especially in the field environment (as early as 34 days after transplanting). All biomulches suppressed weed emergence relative to bare soil, but weeds were visibly growing beneath the most translucent biofabric. Marketable yield of cucumber was trending highest in the most durable and opaque biofabric (1827 g·m−2), but was not significantly different from weed-free bare soil (1251 g·m−2). Relative rate of mulch decomposition up to 11 months after soil incorporation was not different among bioplastic and biofabric products. Results suggest that the tested biofabrics will be most useful to growers when soil warming is not necessary (e.g., warm climates), but moisture conservation and weed control are critical (e.g., organic cropping systems). Moreover, biofabrics are permeable and may be useful to growers dependent on sprinkler irrigation or rainfall to meet crop water demands.

Free access

The recent release of 2,4-D- and dicamba-tolerant soybean traits has increased the risk of off-target herbicide injury and yield loss for specialty crop growers in the midwestern United States. Most dicotyledonous plants, including many specialty crops like pumpkin (Cucurbita pepo), are susceptible to synthetic auxin herbicides; however, the relationship between off-target herbicide rate, visible crop injury, and eventual yield loss is not well documented. The objective of this 2-year field study in 2019 and 2020 was to determine the effect of sublethal herbicide rates of 2,4-D and dicamba on visible injury and crop yield loss in pumpkin when applied at the vegetative and flowering growth stages. Herbicides included 2,4-D choline salt (1066 g ae·ha−1 labeled rate) and dicamba diglycolamine salt (560 g ae·ha−1 labeled rate) ranging from 1/500 to 1/4 of the labeled rate. Visible injury ratings were recorded every 7 d after application and pumpkins were harvested and weighed when ripe. Injury and yield data were fit to a four-parameter log-logistic regression model to estimate effective doses (ED) required for 5% to 50% visible injury or yield loss. Pumpkin treated with the 1/10 and 1/4 rates of 2,4-D at both growth stages had visible injury (± 1 SE) ranging from 8% (± 3%) to 55% (± 3%), but injury did not always result in yield loss. Maximum yield loss from 2,4-D was 32% (± 2%), observed following the 1/4 rate at the vegetative growth stage in 2020 (estimated ED for 20% yield loss was ∼1/50). Pumpkin treated at the vegetative growth stage with the 1/10 and 1/4 rates of dicamba resulted in 65% (± 6%) to 82% (± 1%) visible injury and 33% (± 2%) to 86% (± 14%) yield loss (estimated ED for 20% yield loss was ∼1/10 in 2019 and ∼1/15 in 2020). At the flowering stage, dicamba rates of 1/10 and 1/4 caused visible injury of 31% (± 2%) to 74% (± 5%) and yield loss of 26% (± 10%) to 60% (± 14%) (estimated ED for 20% yield loss was ∼1/20 in 2019 and ∼1/5 in 2020). Susceptibility of pumpkin to 2,4-D and dicamba suggests herbicide applicators and pumpkin growers should consider strategies that mitigate off-target movement, including using nozzles that increase droplet size, shielded sprayers, thorough tank cleanout, buffer zones, and programs that facilitate communication between applicators and growers.

Open Access

Biobased sprayable mulch (BSM) films are a potential alternative to herbicides, polyethylene plastic mulch film, and hand weeding for specialty crops. We developed a series of BSM films using locally available biomaterials [including corn (Zea mays) starch, glycerol, keratin hydrolysate, corn gluten meal, corn zein, eggshells, and isolated soy (Glycine max) protein] and tested their effects on weeds and crop yield during a total of seven greenhouse or field trials between 2017 and 2019 in Nebraska, USA. Application rates of BSM films applied in pots (greenhouse), planting holes in plastic film (field), or bed tops (field) ranged from 0.9 to 18.2 L⋅m−2; they were applied before and after the emergence of weeds. Weed control efficacy was variable, and results of greenhouse pots were rarely replicated under field conditions. Increasing the viscosity of the final suspension tested [BSM7; a mix of corn starch (72.8 g⋅L−1), glycerol (184.7 mL⋅L−1), keratin hydrolysate (733.3 mL⋅L−1), corn zein (19.8 g⋅L−1), and isolated soy protein (19.8 g⋅L−1)] reduced weed biomass by more than 96% in field-grown kale (Brassica oleracea var. sabellica) when applied to bare soil bed tops before or after weed emergence, but kale yield in treated plots was not different from the weedy control. The results demonstrated the potential for postemergence applications of BSM films, which increase application timing flexibility for growers. Further research is needed to explore the effects of BSM films on soil properties and crop physiology and yield.

Open Access

Weeds are a top management concern among organic vegetable growers. Abrasive weeding is a nonchemical tactic using air-propelled abrasive grit to destroy weed seedlings within crop rows. Many grit types are effective, but if organic fertilizers are used, this could integrate weed and nutrient management in a single field pass. Our objective was to quantify the effects of abrasive grit and mulch type on weed suppression, disease severity, soil nitrogen availability, and yield of pepper (Capsicum annuum L. ‘Carmen’). A 2-year experiment was conducted in organic red sweet pepper at Urbana, IL, with four replicates of five abrasive grit treatments (walnut shell grits, soybean meal fertilizer, composted turkey litter fertilizer, a weedy control, and a weed-free control) and four mulch treatments (straw mulch, bioplastic film, polyethylene plastic film, and a bare soil control). Abrasive weeding, regardless of grit type, paired with bioplastic or polyethylene plastic mulch reduced in-row weed density (67 and 87%, respectively) and biomass (81 and 84%); however there was no significant benefit when paired with straw mulch or bare ground. Despite the addition of 6 to 34 kg N/ha/yr through the application of soybean meal and composted turkey litter grits, simulated plant N uptake was most influenced by mulch composition (e.g., plastic vs. straw) and weed abundance. Nitrogen immobilization in straw mulch plots reduced leaf greenness, plant height, and yield. Bacterial spot (Xanthomonas campestris pv. Vesicatoria) was confirmed on peppers in both years, but abrasive weeding did not increase severity of the disease. Pepper yield was always greatest in the weed-free control and lowest in straw mulch and bare soil, but the combination of abrasive weeding (regardless of grit type) and bioplastic or polyethylene plastic mulch increased marketable yield by 47% and 21%, respectively, compared with the weedy control. Overall, results demonstrate that when abrasive weeding is paired with bioplastic or polyethylene mulch, growers can concurrently suppress weeds and increase crop N uptake for greater yields.

Free access

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.

Open Access