Broadcast Herbicide Application Research Articles

Agronomic and Technical Evaluation of Herbicide Spot Spraying in Maize Based on High-Resolution Aerial Weed Maps-An On-Farm Trial.

Spot spraying can significantly reduce herbicide use while maintaining equal weed control efficacy as a broadcast application of herbicides. Several online spot-spraying systems have been developed, with sensors mounted on the sprayer or by recording the RTK-GNSS position of each crop seed. In this study, spot spraying was realized offline based on georeferenced unmanned aerial vehicle (UAV) images with high spatial resolution. Studies were conducted in four maize fields in Southwestern Germany in 2023. A randomized complete block design was used with seven treatments containing broadcast and spot applications of pre-emergence and post-emergence herbicides. Post-emergence herbicides were applied at 2-4-leaf and at 6-8-leaf stages of maize. Weed and crop density, weed control efficacy (WCE), crop losses, accuracy of weed classification in UAV images, herbicide savings and maize yield were measured and analyzed. On average, 94% of all weed plants were correctly identified in the UAV images with the automatic classifier. Spot-spraying achieved up to 86% WCE, which was equal to the broadcast herbicide treatment. Early spot spraying saved 47% of herbicides compared to the broadcast herbicide application. Maize yields in the spot-spraying plots were equal to the broadcast herbicide application plots. This study demonstrates that spot-spraying based on UAV weed maps is feasible and provides a significant reduction in herbicide use.

A comparison of seven innovative robotic weeding systems and reference herbicide strategies in sugar beet (Beta vulgaris subsp. vulgaris L.) and rapeseed (Brassica napus L.)

AbstractMore than 40 weeding robots have become commercially available, with most restricted to use in crops or fallow applications. The machines differ in their sensor systems for navigation and weed/crop detection, weeding tools and degree of automation. We tested seven robotic weeding systems in sugar beet and winter oil‐seed rape in 2021 and 2022 at two locations in Southwestern Germany. Weed and crop density and working rate were measured. Robots were evaluated based on weed control efficacy (WCE), crop stand loss (CL), herbicide savings and treatment costs. All robots reduced weed density at least equal to the standard herbicide treatment. Band‐spraying and inter‐row hoeing with RTK‐GPS guidance achieved 75%–83% herbicide savings. When hoeing and band spraying were applied simultaneously in one pass, WCE was much lower (66%) compared to the same treatments in two separate passes with 95% WCE. Hoeing robots Farmdroid‐FD20®, Farming Revolution‐W4® and KULTi‐Select® (+finger weeder) controlled 92%–94% of the weeds. The integration of Amazone spot spraying® into the FD20 inter‐row and intra‐row hoeing system did not further increase WCE. All treatments caused less than 5% CL except for the W4‐robot with 40% CL and the combination of conventional inter‐row hoeing and harrowing (21% CL). KULT‐Vision Control® inter‐row hoeing with the automatic hydraulic side‐shift control resulted in 80% WCE with only 2% CL. Due to the low driving speed of maximum 1 km h−1 of hoeing robots with in‐row elements, treatment costs were high at 555–804 € ha−1 compared to camera‐guided inter‐row hoeing at 221 € ha−1 and broadcast herbicide application at 307–383 € ha−1. Even though the costs of robotic weed management are still high, this study shows that robotic weeding has become a robust, and effective weed control method with great potential to save herbicides in arable and vegetable crops.

Precision weed control using a smart sprayer in dormant bermudagrass turf

Precision herbicide application can substantially reduce herbicide input, thereby cutting chemical costs and minimizing adverse environmental impacts. A smart sprayer prototype was designed and developed for precision herbicide application in turf. This is the first study evaluating the performances of a precision sprayer for weed control in turf in field conditions. The objectives of this research were to 1) evaluate and compare the performances of the traditional broadcast application and a newly developed precision spraying technology for control of weeds in dormant bermudagrass turf, and 2) investigate the influence of weed coverage on the spray volume requirement when using the precision spraying technology developed here. DenseNet, GoogLeNet, and ResNet were evaluated for discriminating the grid cells containing weeds (spray) with the grid cells containing bermudagrass turf exclusively (nonspray). All three neural networks had an F1 score above 0.989 in the validation datasets. ResNet outperformed DenseNet and GoogLeNet with the highest F1 scores (≥0.992) in the testing datasets. Applying herbicide only to turf areas infested with weeds saved a significant amount of the herbicide, while achieving the same level of weed control compared to the broadcast application. The developed precision spraying technology performed well and effectively reduced the amount of herbicide input applied to the dormant bermudagrass turf, compared to the broadcast herbicide application. Overall, the smart sprayer prototype developed in this research can be used for precision weed control in dormant turf, although its design needs to be further optimized.

Silvicultural Treatments Affect Growth and Foliar Nutrients in a Young Ponderosa Pine Stand

Abstract Foliar nutrient status, diameter, and height growth were investigated for young ponderosa pine (Pinus ponderosa) stands grown under six fertilizer and herbicide treatments (including control) in southeast Washington to diagnose foliar nutrient status and evaluate the effects of silvicultural treatments on growth rates. Two application methods of fertilizer (one “best guess” multi-nutrient fertilizer blend) and herbicide applications (broadcast or spot) were used in the study. Broadcast herbicide application produced higher tree growth responses than spot application. The two broadcast application methods improved diameter increments by 43.3%, whereas the average response of the three spot application methods during the third growing season was only 14.5%. Height growth response for these same two treatments was much less than the diameter response. Fertilizer application in addition to herbicide did not significantly increase tree growth over herbicide alone. Foliar nutrient response to fertilization based on foliar vector analysis was inconsistent, possibly due to nutrient imbalances resulting from the one multi-nutrient blend used in our experiment. Control of grass completion produced a rapid posttreatment early growth trajectory and suggested that stand establishment was successful in this plantation. Our results should also be useful in naturally regenerated young ponderosa pine forests subject to heavy grass competition. Study Implications: Given the increasing need for reforestation in the western United States, results from our study should provide useful information for forest managers. Stand establishment is a critical phase for ponderosa pine stands. Broadcast herbicide application in a recently established plantation produced a rapid early growth trajectory. In this experiment, reducing severe sod grass competition was the most important factor that increased tree growth. Our results may also apply to naturally regenerated ponderosa pine stands. Fertilization with a multi-nutrient fertilizer blend did not significantly increase tree growth as a separate treatment or when combined with herbicide. Foliar nutrient response to fertilization was inconsistent, possibly due to nutrient imbalances resulting from the multi-nutrient fertilizer blend used in our experiment. Fertilization rate and nutrient composition trials are needed to develop effective fertilization treatments in young ponderosa pine stands. Based on our results, fertilizing without vegetation control is not recommended when there is heavy grass competition. The grasses proliferated following only fertilization to the detriment of the trees. For the conditions in our study, we cannot recommend adding fertilizer in addition to the herbicide as a treatment because fertilization did not significantly increase tree growth over herbicide alone. We feel fertilization rate and nutrient composition trials are needed to develop effective fertilization treatments in young ponderosa pine stands. The establishment of ponderosa pine forests is vital for the future timber they may produce and the ecological benefits they provide. We recommend broadcast herbicide as an effective silvicultural treatment to control competing vegetation (from grasses in our experiment) during the stand establishment of ponderosa pine. As demonstrated in our study, the rapid posttreatment early growth trajectory from vegetation control suggests that stand establishment was successful.

Uticaj primene herbicida u trake i međuredne kultivacije na svežu masu širokolisnih korova u usevu soje

Aim of the research was to determine whether the band application of herbicides in soybean, covering a 50% smaller herbicide area, in combination with inter-row cultivation can achieve a similar or approximate weed control effectiveness, as compared to the broadcast herbicide application method in soybean crops, with and without inter-row cultivation. In three-year trials, pre-emergence (dimethenamid-P + metribuzin) and post-emergence (bentazon + imazamox) herbicides were applied using the broadcast and band (25 cm wide) application of herbicides, with and without inter-row cultivation.Inter-row cultivation was applied one week after the first and second post-emergence treatments. Impact of the tested variants on the fresh aboveground biomass of weeds was assessed, with the following species being dominant: Abutilon theophrasti Medik., Amaranthus retroflexus L., Ambrosia artemisiifolia L., Chenopodium album L., and Xanthium strumarium L. The results showed that using the band application of herbicides with inter-row cultivation can achieve approximate effectiveness in reducing fresh biomass compared to broadcast application of herbicides, with or without inter-row cultivation. The combination of pre-emergence herbicides and the two-time application of divided amounts of post-emergence band and broadcast application of herbicides with inter-row cultivation achieved the most reliable control of all weeds, with an efficiency >95%. The results indicate that under favorable conditions for the herbicide action, it is possible to omit one half of the total amount of applied post-emergence herbicides. This can further contribute to significantly reducing the total amount of herbicides used in weed control.

Deep Learning-Based Object Detection System for Identifying Weeds Using UAS Imagery

Current methods of broadcast herbicide application cause a negative environmental and economic impact. Computer vision methods, specifically those related to object detection, have been reported to aid in site-specific weed management procedures for targeted herbicide application within a field. However, a major challenge to developing a weed detection system is the requirement for a properly annotated database to differentiate between weeds and crops under field conditions. This research involved creating an annotated database of 374 red, green, and blue (RGB) color images organized into monocot and dicot weed classes. The images were acquired from corn and soybean research plots located in north-central Indiana using an unmanned aerial system (UAS) flown at 30 and 10 m heights above ground level (AGL). A total of 25,560 individual weed instances were manually annotated. The annotated database consisted of four different subsets (Training Image Sets 1–4) to train the You Only Look Once version 3 (YOLOv3) deep learning model for five separate experiments. The best results were observed with Training Image Set 4, consisting of images acquired at 10 m AGL. For monocot and dicot weeds, respectively, an average precision (AP) score of 91.48 % and 86.13% was observed at a 25% IoU threshold (AP @ T = 0.25), as well as 63.37% and 45.13% at a 50% IoU threshold (AP @ T = 0.5). This research has demonstrated a need to develop large, annotated weed databases to evaluate deep learning models for weed identification under field conditions. It also affirms the findings of other limited research studies utilizing object detection for weed identification under field conditions.

Paddy Crop and Weed Discrimination: A Multiple Classifier System Approach

Weeds are unwanted plants that grow among crops. These weeds can significantly reduce the yield and quality of the farm output. Unfortunately, site-specific weed management is not followed in most of the cases. That is, instead of treating a field with a specific type of herbicide, the field is treated with a broadcast herbicide application. This broadcast application of the herbicide has resulted in herbicide-resistant weeds and has many ill effects on the natural environment. This has prompted many research studies to seek the most effective weed management techniques. One such technique is computer vision-based automatic weed detection and identification. Using this technique, weeds can be detected and identified and a suitable herbicide can be recommended to the farmers. Therefore, it is important for the computer vision technique to successfully identify and classify the crops and weeds from the digital images. This paper investigates the multiple classifier systems built using support vector machines and random forest classifiers for plant classification in classifying paddy crops and weeds from digital images. Digital images of paddy crops and weeds from the paddy fields were acquired using three different cameras fixed at different heights from the ground. Texture, color, and shape features were extracted from the digital images after background subtraction and used for classification. A simple and new method was used as a decision function in the multiple classifier systems. An accuracy of 91.36% was obtained by the multiple classifier systems and was found to outperform single classifier systems.

Managing Understory Fagus grandifolia for Promoting Beech Bark Disease Resistance in Northern Hardwood Stands

AbstractMany Allegheny hardwood stands contain dense understories of very shade-tolerant American beech, resulting from partial disturbances that have accelerated root sucker development. The low-shade produced by these sprouts hampers silvicultural regeneration efforts to maintain species diversity in new cohorts. An increasing proportion of sprouts result from stressed trees infested with beech bark disease. The clonal sprouts also have a genetic affinity for the disease. A mixture of Accord® and Oust® herbicides, applied to understory vegetation after shelterwood establishment cuts, can significantly reduce understory beech density. Yet, retention of some overstory beech, with demonstrated disease resistance, is ecologically desirable. The root sprouts from these parent trees should also have resistance to the disease. We used broadcast herbicide application to kill understory vegetation after shelterwood harvests in three stands, and tested the effect of herbicide on beech sprouts associated with resistant trees. Eight years after treatment, plots that had received herbicide had similar densities of beech to no-herbicide plots. However, there were significant differences in seedling densities among stands (P = .0303) and species (P = .0014). Our results indicate that there is much temporal variability in regeneration dynamics after treatment. Resistant beech sprouts are still competitive in the long term, even after herbicide application.

Effects of understory management on trade-offs and synergies between biomass carbon stock, plant diversity and timber production in eucalyptus plantations

Abstract Understory vegetation management is prevalent in successive short rotation eucalyptus plantations to control interspecies competition and improve tree growth and timber yields. Managing for multiple ecosystem services is critical for sustainable forests. Yet trade-offs and synergies between plant diversity, biomass carbon stock, and timber yields under different management approaches is poorly understood. Using eucalyptus plantations under different understory vegetation management approaches, in subtropical China, we examined the effects of understory vegetation management on tree growth, biomass carbon stocks, timber production, the composition and diversity of understory plant communities. We then assessed trade-offs and synergies among biomass carbon stocks, plant diversity attributes and timber production. Manual band tending (manual removal of the above-ground portion of understory vegetation in a 1 m band around the eucalyptus trees) did not affect the diversity of understory plant communities and favored biomass carbon stock and timber production. Thus, this treatment resulted in positive synergies between biomass carbon stock, plant diversity and timber production. Repeated broadcast herbicide application led to declines in understory plant diversity and increased exotic plant invasion, but also improved biomass carbon stock and stand volume. Trade-offs favoring carbon stock and timber production existed in broadcast herbicide application plots. Intensive disturbance of the understory and 0–5 cm topsoil removal led to declines in biomass carbon stock, plant diversity and timber production, and a negative synergy existed among these services. Our results confirm that manual band tending of understory vegetation in eucalyptus plantations, which results in positive synergies among plant diversity, biomass carbon stock, and timber production, should be a favorable management strategy for multiple ecosystem services. Although broadcast herbicide application can effectively improve carbon stock and timber production, attention should be paid to controlling invasive species after application.

Farm‐scale evaluation of herbicide band application integrated with inter‐row mechanical weeding for maize production in four European regions

SummaryTo promote integrated weed management (IWM) implementation in Europe, robust evidence on the sustainability of such tools and strategies is needed to motivate their adoption by stakeholders. This can only be achieved through assessing and validating them at real farm scale and using existing farm equipment, under diverse climatic and soil conditions representative of European agriculture. In 2013 and 2014, 12 on‐farm experiments (i.e. real field conditions on commercial farms, with natural weed flora) were conducted in four important European grain maize‐producing regions comparing the efficacy of herbicide band application integrated with inter‐row mechanical weeding as a potential IWM tool with the conventional broadcast herbicide application (CON) used by the farms. The IWM tools tested were as follows: (i) early post‐emergence herbicide band application combined with hoeing, followed by a second hoeing in southern Germany, (ii) early post‐emergence herbicide band application followed by hoeing in eastern Hungary and central Slovenia and (iii) pre‐emergence herbicide band application followed by hoeing in northern Italy. Herbicide band application integrated with hoeing provided good and partial weed control along and between maize rows respectively. No significant yield differences were detected between IWM and CON. IWM greatly reduced herbicide input and was economically sustainable over the duration of this study with no significant difference in gross margin compared with CON in all cases. This IWM tool could therefore be considered for implementation in European maize systems.

Cotton Response to Nitrogen Derived from Leguminous Cover Crops and Urea Ammonium Nitrate

The use of legumes as a winter cover crop and green manure for subsequent summer annual crops in the southeastern U.S. has been limited due to relatively inexpensive sources of nitrogen. However, the cost of synthetic nitrogen has nearly tripled in the last 11 years, stimulating growers to reconsider the use of legumes as a cost-effective source of nitrogen. Selecting an appropriate legume species, timing of cover crop termination, and timing of summer crop planting can be adjusted to supply total season nitrogen needs of cotton (Gossypium hirsutum L.) in North Carolina. Crimson clover (Trifolium incarnatum L.) and hairy vetch (Vicia villosa Roth) were used as green manures in cotton as a sole source of nitrogen in field experiments conducted in North Carolina during 2010 and 2011. The highest cotton yield and biomass were noted when cover crops were terminated by a single broadcast herbicide application at 10 days before cotton planting. Lint yield of cotton following crimson clover and hairy vetch equaled lint yield of cotton without cover crops plus 70 kg N ha-1 of liquid urea ammonium nitrate. Net return of the legume cover crop/cotton system equaled net return of the cotton liquid nitrogen system and ranged from 1,240 to 1,650 $ ha-1.

Evaluating Restoration Methods across a Range of Plant Communities Dominated by Invasive Annual Grasses to Native Perennial Grasses

AbstractPrairies are imperiled habitats, with remnants being generally small and often existing in isolation. Invasive plants have the potential to invade not just the edge of small remnants but also the interior because smaller remnants experience greater edge effects than do large, contiguous prairies. Additionally, invasive plants limit recruitment of native plants, which can arrest secondary succession. We proposed to assess techniques for restoration that included removing annual grasses and supplementing native species recruitment with seeding of native grass and forb species. We also assessed the effect of specific factors affecting recruitment: soil moisture and seed predation. Treatments included broadcast, spot, or no application of the herbicides imazapic and glyphosate and with or without seeding plus mulch. With treatments nested within each of three plant communities, ranging from annual- to perennial-dominated communities, in four blocks per community, plant characteristics (percentage of cover and plant density), soil moisture availability, and seed-predation losses were measured along a plant community gradient within one season at two locations. A combination of broadcast herbicide application and seeding with mulching was found to be more effective in reducing annual grasses and enhancing the establishment of native grass species in predominately annual and mixed communities (annuals and perennials). Spot herbicide application was effective in predominately perennial communities, whereas only seeding native species did not improve recruitment. Although seed predation reduced seedling recruitment, mulch provided seed protection and enhanced soil moisture retention. Plant community response to imposed treatments differed among communities, suggesting that a decision support tool would facilitate management decisions tailored for each plant community. The decision tool would be useful to ensure that appropriate treatments are applied and that specific factors affecting recruitment, such as seed predation and soil moisture, are addressed.

Survival and growth response of white spruce stock types to site preparation in Alaska

To identify suitable methods for reforestation, we evaluated the interacting effects of past disturbance, stock types, and site preparation treatments on white spruce (Picea glauca (Moench) Voss) seedling survival and growth across a range of sites in Alaska. Replicated experiments were established in five regions. At each site, two complete installations differed in time since disturbance: “new” units were harvested immediately before spring planting and “old” units were harvested at least 3 years before planting. We compared mechanical scarification before planting, broadcast herbicide application during the fall before planting, and no site preparation with 1-year-old container-grown seedlings from two sources, 2-year-old bare-root transplants from two sources, and 3-year-old bare-root transplants. Seedlings were followed for 11 years on most sites. Based on meta-analyses, seedling survival increased 10% with herbicide application and 15% with mechanical scarification compared with no site preparation. Scarification and herbicide application increased seedling height by about 28% and 35%, respectively, and increased seedling volume by about 86% and 195%, respectively, compared with no site preparation. Soil temperature did not differ among site preparation methods after the first 7 years. Results suggest that white spruce stands may be successfully restored through a combination of vegetation control and use of quality planting stock.

Comparison of Fallow Tillage Methods in the Intermediate Rainfall Inland Pacific Northwest

Winter wheat (Triticum aestivum L.) is usually grown in the Pacific Northwest (PNW) intermediate rainfall zone following tilled or chemical summer fallow. Studies were conducted near Davenport, WA and Helix, OR over two fallow–winter wheat cycles to evaluate the efficacy of reduced or no‐tillage fallow compared to conventional fallow and compare the efficacy of herbicides applied using a light‐activated sensor‐controlled (LASC) applicator to broadcast applications. Six treatments included conventional primary tillage followed by rodweeding; sweep‐tillage followed by rodweeding, broadcast, or LASC herbicide application; and no‐tillage followed by broadcast or LASC herbicide application. Broadcast and LASC herbicide applications controlled weeds similarly in no‐tillage treatments. However, LASC applications used from 45 to 70% less herbicide than broadcast applications to attain similar weed control. No‐tillage or sweep‐tillage systems with herbicide application had from 15 to 30% greater surface residue cover than the conventional tillage system. Available soil moisture in both the root‐zone and seed‐zone soil profiles at time of planting was similar among tillage systems. There were no differences in wheat quality parameters across treatments. The conventional tillage system had similar wheat grain yield as sweep‐tillage systems followed by rodweed or broadcast herbicide application, but yields were up to 21% greater than sweep‐tillage with LASC applied herbicides and no‐tillage systems. Reduced tillage systems using sweep‐tillage and broadcast herbicide application could potentially replace more tillage intensive fallow systems in the PNW.

Broadcast vs. Wet-Blade Herbicide Applications for Southern Wax Myrtle (Myrica cerifera) Control

Southern wax myrtle is a pernicious weed in south Florida pastures and this plant can eliminate all forage production under high densities. Previous work has shown that triclopyr at 1.12 kg/ha is the most effective herbicide on this species. The introduction of the Burch Wet Blade (BWB) mowing system provides an alternative application method to traditional broadcast herbicide applications. The objective of this experiment was to compare the efficacy of triclopyr and other herbicides using both broadcast and the BWB application systems. In general, broadcast applications of at least 1.1 kg/ha triclopyr provided better control than the same treatments applied with the BWB system in 1998. In 1999, control was lower overall compared to 1998, but the same trend was observed. Broadcast applications of triclopyr reduced wax myrtle densities better than when herbicides were applied with the BWB system in 1998. However, in 1999, dicamba triclopyr, and at least 1.1 kg/ha triclopyr reduced wax myrtle densities compared to the mow-only treatment, regardless of application method. Although the BWB system provided an initial overall reduction in plant height, recovery of plants was sufficient and often outgrew those receiving broadcast applications of herbicides. Regardless of application method, retreatment of wax myrtle plants 1 yr after the initial application will likely be needed to obtain adequate control.Nomenclature: Imazapyr, triclopyr, dicamba, southern wax myrtle, Myrica cerifera L. MYRCE

Adoption of Integrated Pest Management Tactics by Wisconsin Farmers

Agronomic research and extension personnel generally recognize the benefits of integrated pest management (IPM) but IPM practices have not been rapidly adopted by farmers. In order for applied research and extension programs to be as influential as possible, strategies and tactics must be evaluated in the context of the real-world constraints experienced by farmers. We investigated the linkage between farmers' pest management behaviors, attitudes, and constraints by analyzing an extensive corn pest management survey distributed throughout Wisconsin in 2002. Our objectives were to (1) create a benchmark against which future changes in pest management practices could be detected and (2) explore potential associations between practices and farm characteristics, e.g., farm size or commodity produced. A total of 213 farmers responded with descriptions of their operations; weed, insect, and disease pest management practices; crop consultant usage; interactions with their local agrichemical dealer; and attitudes regarding pest management decision-making. We compared the relative responses of cash-grain and dairy farmers as well as managers of large and small farms. Larger farm size and percentage of operation in cash-grain production were associated with an increased frequency of rotating crops, rotating herbicide families, and use of a broadcast herbicide application. Managers of large farms and/or cash-grain crops also more frequently indicated considering the level of pest control, price, carryover potential, weed resistance management, environmental safety, and risk to the applicator than did dairy or small-sized operations. Cash-grain farmers had significantly higher scores on a calculated IPM index than did dairy farmers (P < 0.0001). We also found a significant positive relationship between farm size and IPM score (P < 0.0001). Our results provide a benchmark for future comparisons of IPM adoption rates in Wisconsin and highlight the association between IPM research/extension and farmers' management behavior.

Effects of Hairy Vetch (Vicia villosa) Cover Crop and Banded Herbicides on Weeds, Grain Yield, and Economic Returns in Corn (Zea mays)

ABSTRACT A two-year field study was conducted during 2002-2003 on a Dundee silt loam soil, Stoneville, MS, to examine the effects of hairy vetch cover crop (HV-D, hairy vetch desiccated at corn planting; HV-B, hairy vetch desiccated in a 38-cm band over crop row at corn planting; and no hairy vetch) and preemergence (PRE) plus postemergence (POST) herbicides applied broadcast and banded on weed control, yield, and economic return in corn. Atrazine plus metolachlor were applied PRE and POST. Bentazon in 2002 and carfentrazone in 2003 were applied in mixture with atrazine plus metolachlor POST. More hairy vetch dry biomass was present in the HV-B system (2,941 kg/ha) than in the HV-D (1,397 kg/ha) and no hairy vetch (0 kg/ha) systems at 7 wk after planting corn (WAP). Live and desiccated hairy vetch in HV-B and HV-D systems suppressed pitted morning glory compared with no hairy vetch at 7 WAP. Densities of barnyardgrass, carpetweed, smooth pigweed, or yellow nutsedge were not reduced in HV-D and HV-B systems compared with no hairy vetch. Hairy vetch cover crop residue in HV-D and HV-B systems had no effect on total weed dry biomass at 7 WAP compared with no hairy vetch. Corn yields were higher in the HV-D system, regardless of herbicide treatment, and the HV-B with broadcast-applied PRE plus POST herbicide treatment compared with no hairy vetch treatments in 2003. Corn yields were similar with band- and broadcast-applied PRE plus POST herbicides when no hairy vetch or all hairy vetch was desiccated at planting (HV-D). Higher costs associated with hairy vetch were offset by higher corn yields in the HV-D system compared with no hairy vetch in 2003, as net returns were similar in both systems. Applying PRE plus POST herbicides in a band resulted in similar net returns as broadcast herbicide application in the no hairy vetch and HV-D systems. These findings indicate that hairy vetch cover crop had little effect on reducing densities of weed species studied, higher costs associated with cover crops can be negated with higher corn yields, and herbicide inputs can be reduced by applying herbicides in a band vs. broadcast without reducing corn yields or economic returns.

Zone herbicide application controls annual weeds and reduces residual herbicide use in corn

Abstract To minimize the chance of surface water contamination by herbicides, farmers need alternative ways to manage weeds in field crops, such as field corn, that reduce herbicide use. Zone herbicide application (ZHA) reduces herbicide use compared with conventional broadcast herbicide application by (1) banding low herbicide rates between corn rows (≤ 1× normal broadcast registered rate), (2) managing crops to favor crop competition, and (3) banding very low herbicide rates over crop rows (≪ 1× normal rate). The research goal was to compare the relative effectiveness of reduced-rate ZHA with broadcast herbicide application on in-row (IR) and between-row (BR) summer annual weed cover (chiefly giant foxtail and waterhemp species), grain yields, and net returns resulting from herbicide application in field corn. Preemergence ZHA of atrazine + metolachlor + clopyralid + flumesulam was made in zones (i.e., even width bands) at different rates between and over crop rows for three site-years in Missouri, and ...

Banded herbicides and cultivation for weed control in potatoes (Solanum tuberosum L.)

Increasing costs of production have resulted in intensified efforts to reduce the amount of herbicides applied in potato production. This research evaluated the potential of applying herbicides in 30-cm-wide bands over the potato row in combination with cultivation between the potato rows to achieve weed control. At a moderate to high infestation of quackgrass and annual broadleaf weeds, control of quackgrass, corn spurry and wild radish was as effective with the banded herbicide + cultivation treatments as with the broadcast herbicide treatment. Potato marketable yields from the banded herbicide + cultivation treatments were comparable to the broadcast herbicide application treatment. A single cultivation at 21 d after planting (DAP) (at ground crack), 28 DAP (potatoes 5 to 10 cm tall) or 35 DAP (potatoes 10 to 15 cm tall) did not give adequate weed control, and potato yields were reduced by 30% or more at all times of cultivation compared to herbicide treatments. This study shows that acceptable weed control without effects on marketable yield is possible by using a 30-cm-wide herbicide band over the row followed by cultivation to remove weeds between the row. The amount of herbicide used per hectare with this technique is reduced by 66% compared to a broadcast herbicide application. Key words: Herbicide, potato, quackgrass, Elytrigia repens L. (Nevski), corn spurry (Spergula arvensis L.), wild radish (Raphanis raphanistrum L.), cultivation

Underplanted conifer seedling survival and growth in thinned Douglas-fir stands

In a multilevel study to determine limits to underplanted conifer seedling growth, Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), grand fir (Abies grandis (Dougl. ex D. Don) Lindl.), western redcedar (Thuja plicata Donn ex D. Don), and western hemlock (Tsuga heterophylla (Raf.) Sarg.) seedlings were planted beneath second-growth Douglas-fir stands that had been thinned to basal areas ranging from 16 to 31 m2/ha. Understory vegetation was treated with a broadcast herbicide application prior to thinning, a directed release herbicide application 2 years later, or no treatment beyond harvest disturbance. Residual overstory density was negatively correlated with percent survival for all four species. Broadcast herbicide application improved survival of grand fir and western hemlock. Western redcedar, grand fir, and western hemlock stem volumes were inversely related to overstory tree density, and this effect increased over time. There was a strong indication that this was also the case for Douglas-fir. Reduction of competing understory vegetation resulted in larger fourth-year stem volumes in grand fir and western hemlock.