Soil tarping is a weed control method used by innovative farmers across the globe. Strategies used by farmers vary in terms of tarping material, time of application, length of time soil is covered, and the production goal. Solarization is a tarping technique that uses clear greenhouse plastic to harness light and energy from the sun to germinate weed seeds in the soil and exhaust the weed seed bank prior to a growing season. Occultation is another tarping technique that uses opaque tarps to warm the soil and stop light from germinating weed seeds or encouraging plant growth beneath the tarp. Researchers have taken an interest in exploring solarization and occultation impacts on weed suppression and soil health. During the 2023 and 2024 growing season, South Dakota State University soil tarping researchers collaborated with farmers across South Dakota to gain insight in farmer application of tarps. Farmer collaborators in South Dakota were each supplied with three tarp materials: black silage tarp, white silage tarp, and clear greenhouse plastic. Each farmer was told to use the tarp how they saw best fit for their operation. Farmers were given the opportunity to engage in field days and presentations to learn more about soil tarping. Each growing season, farmers worked with a team of researchers to collect data on soil temperature, moisture, and nitrogen. This data was collected through soil samples and HOBO moisture and temperature sensors that logged values hourly. Farmers also provided observations, photos, and dates for tarp removal and application along with comments on how well tarping fit into their system. While research studies can provide important details of tarping impacts on weed suppression and soil health, it is important to showcase the reality of how applicable this technique is for farmers in the real world.
Cover crops offer multifaceted benefits including soil health improvement, nutrient management, erosion control, and suppression of pests, diseases and weeds. This study examined the impact of fall cover crop (FCC) for enhanced soil properties and suppression of weeds and diseases, top priorities for chickpea growers. FCC was comprised of winter rye alone (in 2021) or in combination with hairy-vetch (in 2022-2023). To assess soil property changes, 5 quadrants (50 cm x 50 cm) representing each dense (≥ 96%), poor (10-35%) and no-growth (0%) FCC areas were sampled annually in April. Soil nutrients and biomass accumulation was measured and compared. For weed suppression, five treatments were compared: till- green manure (GM), GM plus pre-emergence herbicide (GMH), and no-till after termination via crimp-mulch (CM), kill-mulch (KM) or mow-mulch (MM). In 2023, significantly higher fresh (514 t/ha) and dry (140 t/ha) biomass was added to the soil from densely and sparsely FCC areas, respectively. Weed suppression was better on GMH than GM for the first 6-8 weeks but reached an average of ≥ 67.5% when monitored 92 days after chickpea planting. Similarly, no-till planted chickpeas after CC terminations in 2021 suppressed weeds during early stages but not in 2022. In both years, it was not possible to harvest chickpeas after no-till due to overwhelming weed infestation. Although added organic matter was evident across all years, FCC alone did not significantly suppress weeds in 2022 and 2023. Slightly different results are anticipated with adjustments in termination timing and conditions favoring mulch establishment in 2024 growing season.
Sweetpotatoes (Ipomoea batatas L.) are among the most important food crops worldwide, but production in Missouri is limited. Weed competition, especially early in the growing season, is a major factor impacting sweetpotato yields. The objective of this study was to optimize early season weed control in sweetpotatoes using fall seeded cover crops and spring applied herbicides. Cover crops, cereal rye (Secale cereale L.) or winter wheat (Triticum aestivum L.), were seeded in the fall. Before sweetpotato transplanting the following spring, glyphosate was applied to terminate cover crop growth along with flumioxazin as a residual herbicide. In designated treatments, S-metolachlor was applied 3 weeks later to extend residual activity. A total of eight treatments, including an untreated control, and a second control consisting of herbicides followed by tillage and hand-weeding as Missouri standard practice, were arranged in a randomized complete block design with four replications. Sweetpotato ‘Beauregard’ slips were transplanted in early June 2023. By 4 weeks after transplanting (WATr), weed biomass in cover crop plus herbicide plots was reduced by 99.3% and 86.3% for broadleaf and grass weeds, respectively, compared to the untreated control. An orthogonal test found that sweetpotato production in plots that received winter wheat as cover crop resulted in a significantly higher yield compared to plots that received cereal rye as a cover crop. Winter wheat combined with flumioxazin applied PRE and S-metolachlor applied as an overlapping residual herbicide demonstrated the greatest yield among all treatments, resulting in over 200-fold greater yield compared to the untreated control. The Missouri standard practice, represented as the weed-free control, produced statistically the same yield as the best treatment. However, this was the most time-consuming and labor-intensive practice and would be challenging for commercial production. Collectively, our results suggest that sweetpotato production in Missouri should consider integration of cover crops and herbicides to allow strong establishment of sweetpotato vines early in the early growing season, and hence ensure higher profitability without intensive labor inputs.
The United States ranks second in strawberry production worldwide. Much of this production has been transitioned from perennial matted row to annual plasticulture production. However, in states like Indiana, growers are exploring a hybrid system: multi-year plasticulture production. In response, we explored cover crops for row-middle weed management in plasticulture strawberry production. In September 2022, we planted ‘Chandler’ strawberry plugs into white polyethylene-mulched rows at Lafayette and Vincennes, IN. We established five row-middle treatments: nontreated and wheat straw mulch controls and three cover crops (oats, cereal rye, and white clover). The oats were winter-killed, and the cereal rye was roller-crimped in mid-May of 2023. Data collected included percent cover crop and weed canopy (per 0.09 m2); frost-killed flowers, live flowers, and developed fruits per plant within 2 weeks after the last spring frost; and total fruit number and yield per plant. At 7 weeks after transplanting (WAP), the oats canopy (82%) was greater than that of cereal rye (61%) and white clover (22%) but less than straw mulch (96%). Weed canopy in the straw mulch and oats was 6%, less than the nontreated control (38%). At 27 and 35 WAP, the cereal rye canopy was 96% and 100%, respectively; while the other treatments had less than 85% and 74% coverage, respectively. At 27 WAP, cereal rye and oats at both sites and straw mulch at Vincennes had less weed canopy (< 7%) than the nontreated control (>63%). At 35 WAP, only cereal rye had no weed canopy. At Lafayette, all treatments had 15 frost-killed flowers per plant. At Vincennes, all treatments had 8 frost-killed flowers per plant, except cereal rye (2 frost-killed flowers per plant). There were no differences among treatments in the live flower count. The number of developed fruits at both sites was significantly greater with cereal rye (8 fruits per plant) compared to all the other treatments (≤ 5 fruit per plant). Total harvested fruit number and yield at Lafayette was 17 fruits per plant and 135 g per plant for all treatments. At Vincennes, cereal rye resulted in significantly greater fruit number (10 fruits per plant) and yield (99 g per plant) compared to all other treatments (≤ 5 fruit and ≤ 49 g per plant). This study demonstrated that cereal rye was the most effective choice for suppressing weeds while maintaining or increasing strawberry yield in the first year of a multi-year plasticulture production system.
Palmer amaranth (Amaranthus palmeri) and waterhemp (Amaranthus tuberculatus) are the two most troublesome pigweeds in crop production systems in the United States. These pigweeds just started to appear in the Pacific Northwest (PNW). A coordinated extension and outreach effort among land-grant universities (University of Idaho and Oregon State University), Amalgamated Sugar, other commodity commissions, and industry was launched to track Palmer amaranth and waterhemp in the PNW. In 2023, tissue samples were collected from pigweeds suspected to be Palmer amaranth and waterhemp and sent to Colorado State University for KASP genotyping test to confirm if the species were Palmer amaranth and waterhemp. The KASP test confirmed that the suspected pigweeds were Palmer amaranth and waterhemp. Since the majority of these pigweeds survived multiple applications of glyphosate, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene duplication analysis was conducted to confirm possible glyphosate resistance in the Palmer amaranth and waterhemp populations. About 70% (17 out of 23) of the Palmer amaranth tissue samples showed gene duplication of up to 184 EPSPS gene copies, indicative of glyphosate resistance. All three populations of waterhemp showed gene duplication of 5.7 to 9.2 EPSPS gene copies indicative of glyphosate resistance. The widespread glyphosate resistance in the samples collected suggests that Palmer amaranth and waterhemp being introduced into the PNW are coming from States where these weeds have developed resistance to multiple herbicide groups. This would have huge implications for weed control in vegetables and other crops in the PNW.
In recent years, doveweed [Murdannia nudiflora (L.) Brenan] has become a pressing concern in Florida and nearby regions due to its rapid expansion and challenging eradication. Despite being considered a warm-season annual broadleaf, its grass-like foliage often enables it going unnoticed within the canopy, especially at early growth stages. Such camouflage allows for quick proliferation and rapid invasion leading to dense mats outcompeting desired turfgrass sward. Limited reliable herbicides exist, and their efficacy declines once the plants get established. Hence, there is a demand for options capable of controlling mature populations. This study assessed the efficacy of mesotrione at 0.37 L ha-1 or 0.58 L ha-1, simazine at 1.10 L ha-1 or 1.83 L ha-1, and their combinations for the late-season control of established doveweed in bermudagrass ‘CR-01’ maintained as a golf course fairway or athletic field at West Florida Research and Education Center in Jay, FL. When used independently, mesotrione alone provided inconsistent control, never surpassing 50%, whereas simazine alone yielded a maximum control of 80%) was achieved within 2 to 6 weeks after the initial treatment, contingent upon the rate, with higher rates yielding a more rapid response. Moreover, the control remained persistent until the conclusion of the study. Severe phytotoxicity was evident in all mesotrione-containing treatments, yet the turf recovered to acceptable levels within 4 weeks following each application.
Targeted spray application technologies have the capacity to drastically reduce herbicide inputs but to be successful, performance of both machine vision (MV) based weed detection and actuator efficiency need to be optimized. This study assessed 1) the performance of spotted spurge recognition in ‘Latitude 36’ bermudagrass turf canopy using the You Only Look Once (YOLOv3) real-time multi-object detection algorithm, and 2) the impact of various nozzle densities on model efficiency and projected herbicide reduction under simulated conditions. The YOLOv3 model was trained and validated with a dataset of 1,191 images. The simulation design consisted of 4 grid matrix regimes (3 × 3, 6 × 6, 12 × 12, and 24 × 24) which would then correspond to 3, 6, 12, and 24 non-overlapping nozzles, respectively; covering a 50-cm wide band. Simulated efficiency testing was conducted using 50 images containing predictions (labels) generated with the trained YOLO model and, by applying each of the grid matrixes to individual images. The model resulted in prediction accuracy of a F1 Score of 0.62 precision of 0.65 and recall value of 0.60. Increased nozzle density (from 3 to 12) improved actuator precision and predicted herbicide-use efficiency with a reduction in false hits ratio from ~30% to 5%. The area required to ensure herbicide deposition to all spotted spurge detected within images was reduced to 18% resulting in ~80% herbicide savings compared to broadcast application. Slightly greater precision was predicted with 24 nozzles, but not statistically different from the 12-nozzle scenario. Using this turf/weed model as a basis, optimal actuator efficacy and herbicide savings would occur by increasing nozzle density from one to 12 nozzles with the context of a single band.
The economic significance of hemp (Cannabis sativa L.) as a source of grain, fiber, and flower is rising steadily. However, due to the lack of registered herbicides, hemp growers have limited weed management options. Slow-growing hemp varieties can be outcompeted by weeds for sunlight, water, and nutrients. Hence, easily adoptable integrated weed management (IWM) strategies are essential. Addressing these challenges necessitates novel approaches to identify quantitative phenotypes and explain the genetic basis of key weed-competitive traits. Plant height and canopy architecture may affect crop-weed competition. However, manually measuring these parameters is a time-consuming process. The PlantEye (PE) multispectral 3D scanner was selected as the high-throughput digital phenotyping technology for the evaluation of plant architecture. In this study, the suitability of digital phenotyping was evaluated at the Clemson University Coastal Research and Education Center to screen diverse hemp varieties with different plant habits. Digital plant biomass, plant height, and plant 3D-leaf area (including leaf area index, leaf angle, and light penetration) were periodically monitored. We performed a range of validation tests for morphological features (digital biomass and plant height). A significant correlation (P < 0.001) was observed between digital biomass and manually measured biomass (R = 0.89), as well as between digital height and manually measured height (R = 0.94), indicating the high precision and usefulness of 3D multispectral scanning in measuring morphological traits. Multispectral analyses used in this study are non-destructive, rapid techniques with minimal error and human interference, which have great potential for use in planning weed management.
Managing weeds is one of the most significant challenges, especially in organic vegetable production systems. Farmers control weeds in various ways, many of which can have negative environmental impacts. Cultivation is a common way many organic vegetable growers will manage weeds; however, it leads to decreased soil health properties. Hand weeding is extremely time-consuming and labor-intensive. Conventional herbicides have raised public concern for their impact on human health and the environment. Organic herbicide products are used as a burndown, post-emergence product but can be cost-prohibitive. In addition, there is a lack of current research comparing organic herbicide effectiveness on a range of common weed species. This study aimed to explore the efficacy of five Organic Materials Review Institute-approved organic herbicides. These products included citrus oil (Avenger®), ammonium nonanoate (AXXE®), acetic acid (Green Gobbler®), caprylic acid capric acid (HomePlate®), and clove oil cinnamon oil (Weed Zap®). Water was used as a control, and glyphosate (Ranger Pro®) was used as a positive control. Each herbicide was tested on six common weed species: Chenopodium album (common lambsquarters), Portulaca oleracea (common purslane), Setaria viridis (L.) Beauv. (green foxtail), Digitaria sanguinalis (L.) Scop. (large crabgrass), Amaranthus retroflexus (redroot pigweed), and Abutilon theophrasti (velvetleaf). Products were sprayed according to label recommendations using a calibrated spray chamber at the Iowa State University greenhouses. Each weed species, 10 plants per replication, was sprayed after reaching an average height of seven centimeters. Percent weed cover using digital image analysis software (Turf Analyzer) and percent visual injury was recorded. These data parameters were collected 24 hours, 3 days, 10 days, 17 days, and 21 days following herbicide application. Weed biomass was collected and dried 21 days after herbicide application for all species. AXXE® was a fast-acting herbicide on common lambsquarters, common purslane, redroot pigweed, and velvetleaf. These species showed over 85% injury three days after AXXE® application. Weed Zap® stunted the majority of examined weed species soon after application, but the injury effects were less significant 21 days after application. Visual injury assessments showed Avenger®, Green Gobbler®, HomePlate®, and Weed Zap® had no significant injury on green foxtail and large crabgrass 21 days after herbicide application. Results from this study provide growers with practical and applied data to make informed decisions regarding the use of organic herbicides.
