Article

Herbicide and Mulch Interactions: A Review of the Literature and Implications for the Landscape Maintenance Industry

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Abstract

Use of organic mulch is one of the most common methods of weed control in landscape planting beds and provides other benefits, including improved soil characteristics, increased growth of ornamental plants, and enhanced property aesthetics. In the landscape maintenance industry, it is common to apply mulch and herbicides concurrently to landscape beds to provide long-term, broad-spectrum weed control. It is known that herbicides behave differently when applied to different soil types and organic materials; however, research is lacking concerning which herbicides are most effective with different mulch materials in the landscape. Determining the most effective herbicide–mulch combinations could potentially improve weed control, reduce labor costs from hand weeding, and mitigate negative environmental impacts resulting from off-site herbicide movement. The objective of this paper is to review the research that has been conducted pertaining to various mulch–herbicide combinations in the landscape and in other areas of agricultural production while also identifying key knowledge gaps that should be addressed in future research. Review of the literature suggests satisfactory weed control can be achieved with high mulch depths (≥ 7 cm) regardless of herbicide use, and herbicide–mulch interactions become more pronounced as mulch depth decreases. Additionally, future research is needed to determine which herbicides are best suited for different mulch types to improve weed control and potentially reduce environmental impacts, including herbicide leaching and runoff into urban and suburban waterbodies.

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... To control weeds, various methods have been tested, such as chemical, non-chemical, and the integrated chemical and non-chemical practices (Marble, 2015;Stewart et al., 2017). Chemical weed control primarily uses herbicides to control weeds (Altland et al., 2004) whereas non-chemical weed control utilizes different cultural practices, such as mulching, irrigation, and fertilization to reduce the weed growth (Case et al., 2005;Amoroso et al., 2009;Marble et al., 2019;Saha et al., 2019b). ...
... In Case et al. (2005) published a review on container nursery weed control practices, discussing commonly used herbicides for container nurseries, other control practices (mulching, irrigation, and combining tactics). In Marble (2015) reviewed herbicide and mulch interactions, suggesting that high mulch depths (>7 cm) resulted in a high level of weed control regardless of herbicide use. In Stewart et al. (2017), another review on container nursery and landscape weed control was published, focusing on irrigation, nutrient, and substrate management effects on the weed growth and herbicide performance. ...
... Later, mulches stood out among other non-chemical practices and became a research hot spot due to their easy availability and low prices (Chalker-Scott, 2007). The widely tested mulches, such as pine bark, rice hull, Douglas fir bark, coconut coir, newspaper pellets, and waste paper (Pellett and Heleba, 1995;Penny and Neal, 2003;Amoroso et al., 2009;Mathers and Case, 2010;Chen et al., 2013;Marble, 2015;Bartley et al., 2017;Burrows, 2017;Masilamany et al., 2017;Marble et al., 2019;Massa et al., 2019). Adding mulches (2.54-7.62 cm) can reach satisfactory weed control results depending on mulch types and weed species (Richardson et al., 2008;Cochran et al., 2009;Altland et al., 2016;Massa et al., 2019;Särkkä and Tahvonen, 2020). ...
Article
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Weeds, as one of the biggest challenges in the nursery industry, have been controlled by various methods, such as chemical and non-chemical practices. Although these practices have been widely established and tested to control weeds, there is no systematic or meta-analysis review to provide quantitative weed control efficacy information of these practices. To provide a systematic understanding of weed control practices in nursery production, a visualization research trend, a systematic review, and a meta-analysis were conducted. A total of 267 relevant studies were included for the research trend and 83 were included in the meta-analysis. The results in this study showed that interests in nursery weed control have switched dramatically in the past 2-3 decades (1995-2021) from chemical dominant weed control to chemical coexistent with non-chemical techniques. Developing new management tactics and implementing diverse combinations of integrated weed management present the future trend for weed control. The systematic review results showed that chemical methods had the highest weed control efficacy, while non-chemical had the lowest on average, nonetheless, all three weed control practices (chemical, non-chemical, and combined) reduced the weed biomass and density significantly compared with when no strategy was employed. Weed control challenges could be the catalyst for the development of new non-chemical and integrated weed control techniques.
... Research on the various active ingredients evaluated for weed control in planting beds has been reviewed previously (Marble et 2015b). Similarly, the body of research pertaining to herbicide and mulch interactions and combinations has been summarized and synthesized (Marble, 2015). Overall, the bulk of the research suggests that the best herbicide-mulch combination, from an efficacy standpoint, will largely depend on mulch depth and weed species present, with herbicide active ingredient and rate becoming less significant as mulch depth increases (Marble, 2015). ...
... Similarly, the body of research pertaining to herbicide and mulch interactions and combinations has been summarized and synthesized (Marble, 2015). Overall, the bulk of the research suggests that the best herbicide-mulch combination, from an efficacy standpoint, will largely depend on mulch depth and weed species present, with herbicide active ingredient and rate becoming less significant as mulch depth increases (Marble, 2015). Although many different strategies have been thoroughly evaluated for landscape weed control efficacy, research is lacking on which method or combination of methods is most economical on a yearly basis. ...
... The authors concluded that herbicide losses by photodegradation may have been minimized when applied in conjunction with a mulch, and increased efficacy could further be explained by the physical barrier provided by the mulch layer. Previous research has shown that as mulch depth increases, the benefits of herbicides used in combination with those mulches decrease due to increased light exclusion and the physical barrier provided by herbicides (Marble, 2015). ...
Article
Organic mulch is commonly used in landscape planting beds to improve plant growth and reduce competition from weed species. Although many different mulch materials have been evaluated in landscape, forestry, or agricultural settings, there have been no previous reports concerning the maintenance costs associated with different mulch materials from a weed control perspective. Trials were conducted at two locations in Florida to estimate the annual maintenance costs associated with pine bark nuggets (bark derived from pine species not specified) and pine straw mulch [mix of longleaf pine (Pinus palustris) and slash pine (Pinus taeda) needles] with and without the use of a granular preemergence herbicide when maintained at similar depths in schilling’s holly (Ilex vomitoria ‘Schilling’s Dwarf’) shrub beds and asiatic jasmine (Trachelospermum asiaticum ‘Minima’) groundcover beds. Weed coverage and residual mulch depth were tracked over time, with maximum and minimum thresholds (20% and 2 inches, respectively) set as triggers for maintenance activities. Results showed that the addition of herbicide (trifluralin + isoxaben) had little to no impact on weeding frequency or time when plots were mulched, but did reduce hand weeding frequency and time compared with nontreated, nonmulched plots. Both mulch materials used alone reduced hand weeding frequency and time compared with herbicide-only treatments. Although results varied by bed type and location, pine bark generally provided greater weed control compared with pine straw and required fewer mulch additions and less mulch by volume. Results from this study suggests that using pine bark nuggets as mulch may result in lower maintenance costs and weed pressure compared with pine straw when both are applied and maintained at 2-inch depths.
... The landscape industry represents a diverse network of service companies contributing over $54 billion in sales in the United States (Hodges et al., 2011). Weed management in non-turf areas of residential and commercial landscapes is primarily achieved through application of organic mulch materials that serve as both a weed management tool and provide aesthetic value (Marble, 2015). Materials such as pinebark, pinestraw, hardwood chips from various plant species and other, sometimes inorganic mulches (i.e., gravel or stone) are commonly used due to their low cost and/or availability, and consumer preferences (Chalker-Scott, 2007). ...
... Research has shown that mulch primarily inhibits weed growth through light exclusion (Wesson and Wareing, 1967;Popay and Roberts, 1970;Fitter and Hay, 1987;Richardson et al., 2008), creation of a physical barrier (Crutchfield et al., 1986;Facelli and Pickett, 1991;Marble, 2015), and reducing available water within mulch layers (Jordan et al., 2010). While physical characteristics and depth of mulch often explain efficacy in regards to weed control (Chalker-Scott, 2007), allelopathic properties present in some mulch materials may also inhibit weed growth in certain instances. ...
... Although research has focused on allelopathic properties of various agronomic crop residues and cover crops, and their effect on weed suppression or potential as natural herbicides/herbicide templates (Weston, 2005), these materials would not be suitable in landscapes due to rapid decomposition, availability, and appearance (Marble, 2015). There remains a significant knowledge gap concerning identification and quantification of potential allelochemicals present in the common landscape mulch materials. ...
Article
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Use of organic mulch materials such as pinebark, pinestraw, or various hardwood chips for weed control is a common practice in residential and commercial landscapes. Mulch can inhibit weed seed germination and growth through light exclusion, acting as physical barrier, reducing available moisture to weed seeds within the mulch layer, and through release of allelochemicals that may inhibit germination or growth of some weed species. Previous and current research on allelopathic chemicals present in mulch have focused on cover crops and their residues with an emphasis on agronomic crops. These materials would not be suitable in a landscape setting due to rapid decomposition, lack of commercial availability, and little aesthetic appeal. Research is needed concerning identification, quantification, extraction, mechanism of release, persistence, selectivity, genetic regulation, and mode of action of potential allelochemicals present in mulch materials used for landscape purposes. More knowledge of these natural chemicals could aid practitioners and homeowners in the selection of mulch and identify potential new mulch materials that could be utilized in these industries. The purpose of this review is to summarize previous research pertaining to allelopathic compounds present in commonly used mulch materials and identify new potential mulch materials that could be utilized in the landscape sector based upon allelopathic properties. Current areas where additional research is needed are also identified.
... M ulching is one of the most widely adopted and effective methods of weed control in landscape planting beds (Chalker-Scott, 2007;Marble et al., 2015a). Although mulch is an effective weed management tool, preemergence herbicides may be used in combination with mulch to reduce labor costs associated with hand weeding, repeated application of postemergence herbicides, or both (Marble, 2015;Marble et al., 2015aMarble et al., , 2015bWilen and Elmore, 2007). In addition to weed control benefits, use of common mulch, such as PB or PS, has been shown to reduce runoff and leaching of preemergence herbicides, including pendimethalin, metolachlor, and isoxaben, by 35% to 74% in the landscape compared with application of these herbicides to bare soil (Knight et al., 2001). ...
... In ornamental production, synergistic herbicide and mulch interactions have been reported, as mulch may act as a slow-release herbicide carrier, extending the longevity of weed control, or provide control of weeds when mulch alone or mulch depth is insufficient (Case et al., 2002;Mathers and Case, 2010;Saha et al., 2019). However, observed synergism with herbicides and mulch typically results when mulch is applied at an adequate depth, usually more than 2 inches (Marble, 2015). Herbicide degradation will occur more rapidly than mulch degradation, and after several months, the type and depth of mulch will be the most important factors in terms of weed suppression if sequential herbicide applications are not made (Bartley et al., 2017). ...
Article
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The objective of this research was to determine how mulch type affects adsorption and efficacy of commonly used preemergence herbicides in nurseries and landscapes. Nursery containers were filled with standard potting media and mulched with either pine bark (PB) mini-nuggets (mixed Pinus sp.), pine straw (PS; mixed Pinus sp.), or shredded eucalyptus hardwood (HW; Eucalyptus sp.) at a 2-inch depth. Herbicides including dimethenamid-P + pendimethalin (applied as a tank mix), prodiamine, and indaziflam were applied to mulched containers, watered in, and the mulch was subsequently removed 3 days later. Seeds of garden spurge ( Euphorbia hirta ), large crabgrass ( Digitaria sanguinalis ), and eclipta ( Eclipta prostrata ) were then seeded and used as bioassay species for dimethenamid-P + pendimethalin, prodiamine, and indaziflam, respectively. Chemical assays were also performed using a separate set of pots mulched with PB at 2 inches and treated with the same herbicides. Results from the bioassay experiment showed PS was the only mulch type that did not significantly decrease efficacy of any applied herbicide. Chemical assays showed only 34% of the applied dimethenamid-P reached the soil surface as evidenced by chemical assay, but more dimethenamid-P moved through PB than did pendimethalin (12%) or prodiamine (17%), which adsorbed more strongly. Overall results suggest preemergence herbicides will be strongly adsorbed to organic mulch. However, as mulch is typically more effective on weeds that germinate below the mulch layer, this does not automatically result in reduced efficacy from herbicide + mulch combinations, and the addition of a preemergence herbicide may be effective in reducing weed germination within or on top of the mulch layer.
... The presence of the trash layer in the ratoon crops adds a degree of complexity to weed control strategies. A recent review suggested a strong relationship between the depth or thickness of trash and weed control (Marble, 2015), with any trash layer with a thickness of 7 cm or more giving satisfactory weed control without herbicide application. However, in thinner trash layers where herbicide applications are necessary, interactions between the herbicide and the trash can be pronounced (Marble, 2015). ...
... A recent review suggested a strong relationship between the depth or thickness of trash and weed control (Marble, 2015), with any trash layer with a thickness of 7 cm or more giving satisfactory weed control without herbicide application. However, in thinner trash layers where herbicide applications are necessary, interactions between the herbicide and the trash can be pronounced (Marble, 2015). While some sugarcane ratoons may start with a cane trash mulch of 7 cm or more, the thickness will rapidly decline during the first few months of a ratoon crop, resulting in herbicide-mulch interactions that have implications for weed control. ...
Article
Herbicide runoff from cropping fields has been identified as a threat to the Great Barrier Reef ecosystem. A field investigation was carried out to monitor the changes in runoff water quality resulting from four different sugarcane cropping systems that included different herbicides and contrasting tillage and trash management practices. These include (i) Conventional – Tillage (beds and inter-rows) with residual herbicides used; (ii) Improved – only the beds were tilled (zonal) with reduced residual herbicides used; (iii) Aspirational – minimum tillage (one pass of a single tine ripper before planting) with trash mulch, no residual herbicides and a legume intercrop after cane establishment; and (iv) New Farming System (NFS) – minimum tillage as in Aspirational practice with a grain legume rotation and a combination of residual and knockdown herbicides.
... Mulch can control weed growth, moderate soil temperature, and increase water availability to container-grown plants. Herbicide placement in regards to the mulch layer (i.e., above or below the mulch) is an important factor to be considered because different mulch materials interact differently with various types of herbicides (Marble, 2015). For preemergence herbicides to be effective they must be incorporated into the soil after application; this typically involves application of 0.6 to 1.3 cm (0.3 to 0.5 in.) of irrigation within 3 to 4 days or a few weeks after application to "activate" the herbicide. ...
... Herbicides need to be irrigated after application to be incorporated or "activated" (Altland et al., 2003), but very little research has been conducted to examine whether more irrigation is needed to improve efficacy in mulched areas (Marble, 2015). The result from this trial showed that when using herbicides, activation irrigation levels of 1.3, 2.5, and 5.1 cm (0.5, 1, or 2 in.) had no impact on efficacy when applied on mulched surfaces. ...
Article
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This research was conducted to assess the impact of herbicide formulation, mulch type and depth, and activation moisture on germination and growth of crabgrass (Digitaria sanguinalis), garden spurge (Chamaesyce hirta), and eclipta (Eclipta prostrata). Granular or liquid formulations of indaziflam, prodiamine, and dimethanamid-P + pendimethalin were evaluated for control of these weed species by in combination with either pinestraw, pinebark, or hardwood mulch at depths of 0, 2.5, or 5.1 cm (0, 1 or 2 in.) followed by herbicide activation irrigation levels (one-time irrigation level following treatment) of either 1.3, 2.5, or 5.1 cm (0.5, 1, or 2 in.). Weed seed placement (below or above the mulch layer) and light penetration through different types and depths of 0, 1.3, 2.5, 5.1, and 10.2 cm (or 0, 0.5, 1, 2, and 4 in., respectively) of mulches were also analyzed. Results showed when using herbicides, mulch depth and herbicide formulation had a greater effect on weed control compared with mulch type or herbicide activation irrigation level. Mulch depths of 5.1 cm (2 in.) and liquid formulations generally provided the highest degree of weed control. There were no differences in light penetration or weed counts when mulch was applied at levels of at least 2.5 cm (1 in.).
... Organic mulches have even been shown to reduce emergence and establishment of some of the most troublesome weeds (Marble 2015). Benefits from organic mulches are well established and a wide variety of mulch products are available for landscape use (Chalker-Scott 2007). ...
... Improved herbicide efficacy was reported from studies where herbicides were sprayed to above, under or a pretreatment on the organic mulch over nursery containers (Chen et al. 2013;Somireddy 2012). However, there are no 'herbicide placement' recommendations on pre-emergence herbicide labels in terms of above or under mulch layers (Marble 2015). ...
Article
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A combination of oil palm frond (OPF) mulch and imazathapyr has been shown to provide great inhibition of weed but its phytotoxicity may be influenced by imazethapyr placement on the OPF mulch and rainfall amount. This study aimed to evaluate effects of herbicide placement and rainfall amount on the phytotoxic activity of imazethapyr in combination with OPF mulches against goosegrass, slender cyperus and coat buttons under glasshouse conditions. Imazethapyr was applied at 10.4 g a.i. ha-1 to under or above or as a pretreatment on the OPF mulch residue powder (> 2 mm) at 3.5 t ha-1. Imazethapyr placement did not influence its inhibitory effects against weed emergence. Both pretreated mulches and imazethapyr applied under the mulches had comparable inhibition of seedling growth for goosegrass and slender cyperus. However, the pretreated mulches gave better seedling growth inhibition of both bioassay species as compared to those of imazethapyr that applied above mulches. Coat button was highly inhibited regardless of any imazethapyr placements. An increase in rainfall amount from 150 to 450 mm could increase the seedling emergence of goosegrass and slender cyperus from 30 to 80% when subjected to pretreated mulches. However, different rainfall amounts had no significant effect on coat buttons seedling emergence. The pretreated mulches could reduce weed seedling growth by 75 to 80% without being affected by the rainfall amounts. The present results suggested that phytotoxic activity of imazethapyr in combination with OPF residue mulches is dependent on imazethapyr placement, rainfall amount and weed species. © 2019 Penerbit Universiti Kebangsaan Malaysia. All rights reserved.
... Satisfactory weed control can be achieved with high mulch depths (> 70 mm) (Marble, 2015). Although the mechanism responsible for weed control is not well understood for all mulch types (Chalker-Scott, 2007), for most weed species, control can be attributed predominantly to light exclusion (Teasdale and Mohler, 2000). ...
... Although the mechanism responsible for weed control is not well understood for all mulch types (Chalker-Scott, 2007), for most weed species, control can be attributed predominantly to light exclusion (Teasdale and Mohler, 2000). Mulches can also act as a physical barrier to weed germination and growth (Marble, 2015). Certain mulch material, like rye (S. cereale L.), may also control weeds by leaching allelopathic chemicals (Chalker-Scott, 2007). ...
... In such systems, crop residue is retained on the soil surface whereby farmers gain many advantages, such as reduced soil erosion, reduced soil evaporation, increased microorganism activity and reduced weed seed germination [8][9][10]. In conservation agriculture, the application of pre-emergence (PRE) herbicides is highly recommended for the reduction of labor costs, the reduced need for costly post-emergence herbicides and an overall increase in weed suppression and control duration [11][12][13]. ...
... Khalil et al [39] reported a higher prosulfocarb, pyroxasulfone, and trifluralin interception when increasing the crop (wheat, barley, canola, chickpea and lupin) residue from 2 to 4 t ha -1 and lower herbicide efficacy with crop residue present. Furthermore, PRE herbicide efficacy may depend on herbicide physicochemical properties in conservation agriculture systems [13,21,22,25]. For example, herbicides such as pendimethalin may be exposed to high volatilization and photodegradation with crop residue retention [40]. ...
Article
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In conservation agriculture systems, farmers gain many advantages from retaining crop residue on the soil surface, but crop residue retention in these systems may intervene with the activity of pre-emergence herbicides. A pot study was conducted to evaluate the effect of different rates of pre-emergence herbicides [imazethapyr (100 and 150 g a. i. ha⁻¹), isoxaflutole (100 and 200 g a. i. ha⁻¹), metolachlor (1.5 and 2.25 kg a. i. ha⁻¹), pendimethalin (2.25 and 3.38 kg a. i. ha⁻¹) and prosulfocarb + metolachlor (2.5 and 3.75 kg a. i. ha⁻¹)] on seedling emergence and biomass of Echinochloa colona and Chloris virgata when applied in the presence of sorghum residue at rates equivalent to (0, 3 and 6 t ha⁻¹). When seeds of E. colona and C. virgata were not covered with sorghum residue, the seedling emergence and biomass of both weeds was inhibited by 93–100% and 56–100%, respectively, with the application (both rates) of isoxaflutole, metolachlor, pendimethalin and prosulfocarb + metolachlor. Using sorghum residue resulted in lower herbicide efficacy on both weeds. At 3 t ha⁻¹ sorghum residue, E. colona emergence and biomass reduced by 38–100% and 30–100%, respectively, with application of isoxaflutole, metolachlor and pendimethalin (both rates) in comparison with the no-herbicide treatment. Similarly, the emergence and biomass of C. virgata was also reduced by 92–100% and 25–100%, respectively. The results of this study suggest that crop residue may influence efficacy of commonly used pre-emergence herbicides and that the amount of crop residue on the soil surface should be adjusted according to the nature of the pre-emergence herbicides to achieve adequate weed control.
... Various pre-and post-emergence herbicides are used for weed management in the RWCS. However, the efficacy of pre-emergence herbicides is reduced by retaining crop residue on the soil surface [104]. The presence of crop residue on the surface results in more interception of herbicides on the surface, thus inhibiting it from reaching the soil surface. ...
Article
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The rice–wheat cropping system (RWCS) has substantially contributed in making India self-sufficient in food grain production; however, rice residue management is of great concern, threatening the sustainability of this system. Rice residue is invariably disposed of by farmers through open burning. In addition to environmental pollution, residue burning of rice also leads to loss of soil nutrients. One of the alternatives to overcome these problems and sustain the RWCS is managing the rice residues in the field itself. Rice residue retention has variable effects on agricultural pests (namely, weeds, insect pests, diseases, and rodents) in the RWCS. High weed infestation in the RWCS results in high consumption of herbicides, which leads to several ecological problems and evolution of herbicide resistance. The shift from intensive tillage to conservation tillage causes major changes in weed dynamics and herbicide efficacy. Incorporation of rice residue reduces weed density and helps in improving soil physical, chemical, and biological properties. Rice residue retention on the surface or mulching reduces weed density and the biomass of both grass and broadleaf weeds in wheat crop as compared to its removal. Long-term field studies involving the use of rice residue as a component of integrated weed management strategies are needed to be done in the RWCS.
... This situation requires careful analysis for adjustments of herbicide rates to compensate for these losses; however, aspects related to the herbicide selectivity should be consid-ered to avoid crop injury in case of early rainfalls, as well as those related to the sensitivity of the target weeds, and to mitigate negative environmental impacts from the movement of herbicides (Marble, 2015). ...
... A review of earlier research focusing on the use of mulch in combination with, or in comparison with, PRE herbicides was recently published by Marble (2015). In many cases, research focused on evaluating different mulch or herbicide + mulch combinations to determine the most effective on target weed species, or evaluated the use of herbicide-treated mulches Mathers, 2006a, 2006b). ...
Article
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Mulch is often applied in landscape planting beds for weed control, but little research has focused specifically on mulch and preemergence (PRE) herbicide combinations. The objectives of this research were to determine the efficacy of herbicide + mulch combinations and which factors significantly affected weed control, including herbicide formulation and posttreatment irrigation volumes. Additional objectives were to determine efficacy derived from mulch or herbicides used alone under herbicide + mulch combinations and to identify differences in the additive (herbicide + mulch combinations) or singular (herbicide or mulch) effects compared with the use of herbicides or mulch only. Large crabgrass ( Digitaria sanguinalis ), garden spurge ( Euphorbia hirta ), and eclipta ( Eclipta prostrata ) were used as bioassay species for prodiamine, dimethenamid-P + pendimethalin, and indaziflam efficacy, respectively. The experiment consisted of a factorial treatment arrangement of two herbicide formulations (granular or spray applied), three mulch types [hardwood chips (HWs), pine bark (PB), and pine straw (PS)], two mulch depths (1 and 2 inches), and three levels of one-time, posttreatment irrigation volumes (0.5, 1, and 2 inches). Three sets of controls were used: the first set included three mulch types applied at two depths receiving only 0.5-inch irrigation volume, the second set included only two herbicide formulations and three one-time irrigation volumes, whereas the last set received no treatment (no herbicide or mulch) and only 0.5-inch irrigation volume. High levels of large crabgrass and garden spurge control (88% to 100%) were observed with all herbicide + mulch combinations evaluated at mulch depths of 1 inch or greater. When comparing mulch types, the best eclipta control was achieved with hardwood at 2 inches depth. The spray formulation of indaziflam outperformed the granular formulation in most cases when used alone or in combination with mulch. Overall, the results showed that spray formulations of prodiamine and dimethenamid-P + pendimethalin were more effective than granular formulations when applied alone, whereas indaziflam was more effective as a spray formulation when used both alone and in combination with mulch. Increasing irrigation volume was not a significant factor for any of the herbicide + mulch combinations when evaluating overall weed control.
... Weed control in the landscape is a major component in maintaining properties. Chemical weed control underneath shade trees along with the aesthetic appeal of mulching is a commonly used landscape practice (Marble 2015). ...
Article
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Studies were conducted at the E.V. Smith Research Center in Shorter, AL (32°43′N, -85°89′W) in 2013 and 2014 to evaluate herbicides suitable for providing season-long weed control in pecan orchards. Herbicide treatments included: (1) glyphosate applied at 1.12 kg ae·ha−1 (1.0 lb ae·A−1), (2) glyphosate at 1.12 kg ae·ha−1 + indaziflam at 73.1 g ai·ha−1 (1.04 oz ai·A−1), (3) glyphosate at 1.12 kg ae·ha−1 + flumioxazin at 422 g ai·ha−1 (6.02 oz ai·A−1) + pendimethalin at 4.25 kg ai·ha−1 (3.79 lb ai·A−1), and (4) a nontreated control. Glyphosate + indaziflam provided the highest weed-free area at all rating dates, but at 150 DAT (69%) it wasn't acceptable. Glyphosate + flumioxazin + pendimethalin provided a similar weed-free area to glyphosate + indaziflam 30 DAT (88%). Index words: landscape weed control, shade trees, pecan, edible landscape. Species used in this study: Carya illinoinensis (Wang.) K. Koch ‘Desirable'. Chemicals used in this study: indaziflam (Alion®), glyphosate (Cornerstone Plus), flumioxazin (Chateau ®), pendimethalin (Prowl H20®).
... Hence, these natural chemicals can act as alternatives to synthetic herbicides for controlling weeds in case of herbicide-sensitive ornamentals • https://doi.org/10.21273/HORTTECH04652-20 (Marble, 2015). To our knowledge, no research has been published on how different mulch extracts with allelopathic properties can control common liverwort in greenhouse and nursery container production. ...
Article
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Common liverwort ( Marchantia polymorpha ) is a primitive, spore-bearing bryophyte that thrives in containerized ornamental crop propagation and production environments. It is one of the major weed problems in container nurseries and greenhouses because it competes with ornamental plants for soil/growing medium, nutrients, water, space, and oxygen within the container. As a result, its presence can reduce the overall quality and market value of the ornamental crop. Once established in nurseries and greenhouses, it spreads rapidly because of its ability to propagate both asexually and sexually. Currently, no effective methods of controlling common liverwort in container production systems are available because a significant knowledge gap exists. Therefore, research is needed to determine whether organic mulches (types, depths, moisture holding capacity, and particle size), biopesticides, and strategic placement of fertilizers within containers suppress or inhibit common liverwort growth and development. In addition, newer chemicals (both synthetic and organic) and combinations need to be tested on different growth stages of common liverwort. The objective of this review was to summarize previous and current research related to common liverwort control in container production, and to identify areas where additional research is needed either to improve current control methods or to develop new ones.
... Although mulches are multifunctional and in green areas, they are applied mainly for aesthetic purposes, mulching is one of the most effective methods for non-herbicide weed control [75]. Mulches can act only as a physical barrier that limits access of light to germinated weeds and reduces their ability to photosynthesis. ...
Chapter
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Contamination of the soil environment mostly is identified with industry, especially mining and road transport. Unfortunately, also in the commercial horticulture, there are numerous problems concerning the contamination of soils and substrates. Sources of contamination can be fertilizers and waste materials polluted by heavy metals, particularly by cadmium. In the greenhouses where traditional methods of cultivation are used, the soil pollution due to the application of excessively high doses of fertilizers constitutes an environmental hazard. Much faster similar effect occurs in greenhouses where an open system of fertigation is used. In addition to mineral impurities, organic compounds emitted by the plant or that are formed during decomposition of organic matter are the problem. This phenomenon is called allelopathy. In practice, it concerns the monoculture and perennial crops and especially is observed in nurseries, orchards, plantations of berries and asparagus. For this reason, in the later section, the soil sickness, replantation problem and toxicity of mulches in green areas are also discussed.
... In the landscape management and maintenance, applying herbicides above or below the mulch and incorporated in the mulch, commonly provides long-term and broad-spectrum weed control (Case & Mathers 2006;Marble 2015). Nevertheless, herbicides behave differently when applied to different organic materials (Case et al. (Martins & Mermoud 1998;Plimmer et al. 2002;Shaner 2014;Taylor et al. 2000) 257 Chen et al. (2013) reported that the application of EPTC above pine mulch provided 70% control of yellow nutsedge (Cyperus esculentus L.), however, when EPTC applied beneath the mulch exhibited 85% reduction in C. esculentus. ...
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The combination of mulch and herbicide is a promising method for weed control which could reduce the frequency of hand weeding. This study was conducted to evaluate the phytotoxic effects of Elaeis guneensis var. tenera (oil palm) frond (OPF) mulch in combination with several pre emergence herbicides on the inhibition of goosegrass (Eleusine indica (L.) Gaertn), slender cyperus (Cyperus distans L.f.) and coat buttons (Tridax procumbens (L.)) under greenhouse conditions. Three rates of dinoterb, oxyfluorfen, and isoxaflutole were respectively, applied with or without OPF mulch at 3.5 t ha−1. The results showed that the weed inhibition provided by the dinoterb-treated OPF mulch (60 to 100%) was greater than dinoterb (0 to 50%) or OPF mulch (0 to 60%) applied alone across all the application rates and bioassay species. The oxyfluorfen-treated OPF mulch also gave greater inhibition (70 to 90%) of T. procumbens than those provided by oxyfluorfen (20 to 40%) or the OPF mulch alone (55 to 60%). However, an increase in inhibition of C. distans and E. indica was only evident at a low rate of oxyfluorfen when combined the OPF mulch. Weed inhibition was noted with increasing rates of isoxaflutole alone but the isoxaflutole-treated OPF mulch did not lead to further inhibition of weeds except for T. procumbens. These results suggest that the phytotoxicity of OPF mulch in combination with herbicides are dependent on weed species, herbicides, and application rates, with dinoterb being the most compatible with OPF mulch when combined.
... The effectiveness of weed protection when using a thick layer of organic mulch is so high that the simultaneous application of chemical preparations may not produce the expected result, e.g. due to the difficulty in displacement of or interaction with organic matter (Marble, 2015). ...
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The publication presents the current state of knowledge regarding the importance of mulching in the cultivation of Cucurbitaceae (cucurbit, or gourd family) vegetables. The intensifying climate change – mainly decreasing rainfall – combined with large-scale production of cucurbit vegetables worldwide prompt the application of methods that reduce evaporation and weed infestation. One of the widespread methods is mulching of the soil. The most important advantages of this treatment include the efficient use of water, the reduction in soil erosion and in the leaching of nutrients to the deeper layers. In addition, mulching improves the physical and chemical properties of the soil, and positively affects the surrounding microclimate of the plant. The report includes descriptions of the characteristics of various types of organic, mineral and synthetic mulches used. The results of studies on the environmental conditions forming in mulched soil are presented. Also, the results of research into the physico-chemical properties of mulch-covered soil are collated. The effect of mulching on cucurbit vegetables was evaluated in terms of plant growth and development as well as fruit yield and its biological value. The monograph also deals with the effect of mulching on weed infestation, as well as the occurrence of harmful and beneficial organisms.
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Greenhouse and outdoor container experiments were conducted to determine garden spurge and large crabgrass emergence when seeds were placed either on top or below three different mulch materials [pine bark (PB), hardwood (HW), or pine straw (PS)] applied at five depths (0, 1.3, 2.5, 5.1, and 10.2 cm). To elucidate mulch characteristics that contributed to weed control, photosynthetic active radiation ( PAR ) was recorded underneath each mulch layer, moisture retention was monitored for 24 h following irrigation, and particle size was determined using standard soil sieves. Hardwood reduced PAR (97%) more than PB (90%) or PS (92%) at 1.3 cm, but few or no differences were noted between mulches at higher mulch depths. Hardwood also contained the highest percentage of small particles, and consequently retained more water (29%), than PB (14%) or PS (22%) 24 h following a simulated irrigation event. Emergence of large crabgrass and garden spurge was consistently higher when seeds were placed on top of the mulch, compared to seeds placed below. Emergence of both species also tended to respond to increasing depth in a quadratic manner, indicating that once a critical level of mulch was applied (2.5 to 5 cm), further reductions in weed emergence would not be observed, at least over the short-term (12 weeks). Pine bark and PS tended to provide a greater reduction in emergence of both species compared to HW. This research also indicates that larger particle materials, such as PB or PS would be advantageous due to their ability to suppress weed emergence regardless of seed position.
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Crop residue retention could affect the emergence and biomass of weeds in different ways. A summer and winter pot study was conducted to evaluate the effect of different amounts of sorghum and wheat residue on the emergence and biomass of 12 summer and winter Australian weeds. The equivalent amount of sorghum residue to 0, 1, 2, 4 and 6 t/ha was used in the summer study and winter weed seeds were covered with wheat residue equivalent to the amount of 0, 1, 2, 4 and 8 t/ha in the winter study. The emergence and biomass of Amaranthus retroflexus and Echinochloa colona was not affected by sorghum residue treatment. For other summer weeds, the use of the 6 t/ha sorghum residue treatment resulted in 59–94% reductions in biomass compared to no‐sorghum residue retention. Similarly, the application of 8 t/ha wheat residue in the winter study resulted in a reduced biomass of 15–100% compared to no‐crop residue treatment. The results demonstrated the high potential of using crop residues in eco‐friendly weed management strategies, such as harvest weed seed control tactics.
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Mulches provide aesthetic, economic and environmental benefits to urban landscapes. Mulching is especially useful in the establishment of trees in landscapes that receive minimal care, such as restoration sites. In general, mulches improve soil health, creating healthy populations of plants and associated animals. These biodiverse, stable landscapes are more resistant to stress, are more aesthetically pleasing, require fewer applications of pesticides and fertilizers, and are ultimately more sustainable than those without mulch cover. All mulches are not created equally, however, and this review compares the costs and benefits of landscape mulches as reported in the scientific literature. It also presents real and perceived problems associated with various landscape mulches.
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Container production has increased rapidly in many parts of the U.S. over the past 15 years. Container production has been the fastest growing sector in the nursery industry and the growth is expected to continue. Weed growth in container-grown nursery stock is a particularly serious problem, because the nutrients, air, and water available are limited to the volume of the container. The extent of damage caused by weeds is often underestimated and effective control is essential. Various researchers have found that as little as one weed in a small (1 gal) pot affects the growth of a crop. However, even if weeds did not reduce growth, a container plant with weeds is a less marketable product than a weed-free product. Managing weeds in a container nursery involves eliminating weeds and preventing their spread in the nursery, and this usually requires chemical controls. However, chemical controls should never be the only management tools implemented. Maximizing cultural and mechanical controls through proper sanitation and hand weeding are two important means to prevent the spread and regeneration of troublesome weeds. Cultural controls include mulching, irrigation methods (subirrigation), and mix type. Nursery growers estimate that they spend $500 to $4000/acre of containers for manual removal of weeds, depending on weed species being removed. Economic losses due to weed infestations have been estimated at approximately $7000/acre. Reduction of this expense with improved weed control methodologies and understanding weed control would have a significant impact on the industry. Problems associated with herbicide use in container production include proper calibration, herbicide runoff concerns from plastic or gravel (especially when chemicals fall between containers) and the need for multiple applications. As with other crops, off-site movement of pesticides through herbicide leaching, runoff, spray drift, and non-uniformity of application are concerns facing nursery growers. This article reviews some current weed control methods, problems associated with these methods, and possible strategies that could be useful for container nursery growers.
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Chemical weed control is an important weed management option in nursery crop production and landscape maintenance. Improved methods of herbicide delivery can increase efficacy of chemical control and minimize off-site movement, applicator exposure, and incorrect herbicide application. Certain innovative technologies show potential for addressing these issues in the nursery industry. Slow-release herbicide tablets have shown promise in container production. Horticultural collars, treated paper, and treated mulch are potential ways of applying herbicides in container crop production and/or landscape maintenance. Horticultural collars contain herbicides between two layers of a carrier such as a landscape fabric. A rapidly degradable paper can be pretreated with an herbicide for a precise application rate. Mulch can be treated with a herbicide prior to use in the landscape for improved weed control. Herbicides applied through the clip-cut pruning system could control weeds selectively in nurseries and landscapes. Each of these methods may address one or more concerns about off-site movement, calibration, and applicator exposure to pesticides.
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Economic contributions of the green industry in each state of the United States were estimated for 2007-08 using regional economic multipliers, together with information on horticulture product sales, employment, and payroll reported by the U.S. Economic Census and a nursery industry survey. Total sales revenues for all sectors were $176.11 billion, direct output was $117.40 billion, and total output impacts, including indirect and induced regional economic multiplier effects of nonlocal output, were $175.26 billion. The total value added impact was $107.16 billion, including employee compensation, proprietor (business owner) income, other property income, and indirect business taxes paid to state/local and federal governments. The industry had direct employment of 1.20 million full-time and part-time jobs and total employment impacts of 1.95 million jobs in the broader economy. The largest individual industry sectors in terms of employment and value added impacts were Landscaping services (1,075,343 jobs, $50.3 billion), Nursery and greenhouse production (436,462 jobs, $27.1 billion), and Building materials and garden equipment and supplies stores (190,839 jobs, $9.7 billion). The top 10 individual states in terms of employment contributions were California (257,885 jobs), Florida (188,437 jobs), Texas (82,113 jobs), North Carolina (81,113 jobs), Ohio (79,707 jobs), Pennsylvania (75,604 jobs), New Jersey (67,993 jobs), Illinois (67,382 jobs), Georgia (66,042 jobs), and Virginia (58,677 jobs). The total value added of the U.S. green industry represented 0.76% of U.S. Gross Domestic Product (GDP) in 2007, and up to 1.60% of GDP in individual states. On the basis of a similar previous study for 2002 (Hall et al., 2006), total sales of horticultural products and services in 2007-08 increased by 3.5%, and total output impacts increased by 29.2%, or an average annual rate of 5.8% in inflation-adjusted terms.
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The role of forestry plantation residues (leaf and branch) in the suppression of establishment of four weed species (Conyza sumatrensis, Trifolium spp., Echinochloa utilis and Lactica sativa) was investigated. Of the three residue types used, Pinus patula residues were found to have the greatest suppressive effects, followed by Eucalyptus grandis and then Acacia mearnsii. Medium-grade residue was found to be more effective than either the coarse or fine grades, and positioning the weed seeds below the mulch resulted in greater suppression than when placed above it. Water extracts from the three residues also resulted in significant suppression of weed establishment, suggesting an allelopathic effect. Finally, suppression of the dicotyledon species was generally greater than suppression of the grass used in this study.
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Herbicide use is an important component of weed management in field nursery crops. No single herbicide controls all weed species. Oxyfluorfen, simazine, and isoxaben are preemergence herbicides effective against broadleaf weeds. Oryzalin, pendimethalin, and prodiamine are effective in preemergence control of grasses and some small-seeded broadleaf weeds. Metolachlor is the only herbicide currently labeled for nursery crops that is effective in preemergence nutsedge (Cyperus) control. Fluazifop-butyl, sethoxydim, and clethodim are selective postemergence herbicides used for grass control. Glyphosate, paraquat, and glufosinate are nonselective postemergence herbicides used in directed spray applications for broad-spectrum weed control. Bentazon, halosulfuron, and imazaquin are effective postemergence nutsedge herbicides. These herbicides are discussed with respect to their chemical class, mode of action, labeled rates, and current research addressing their effectiveness in nursery crops.
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Shredded and chipped wood mulches are used for weed suppression in perennial fruit crops, in urban landscapes, and occasionally in vegetable crops. Wood chip mulches with weed-suppressing allelochemicals may be more effective for weed control, especially under sustainable and organic production systems, than mulches without such properties. The objective of this study was to test for the presence of water-soluble allelochemicals in wood chips derived from tree species, often found in wood resource recovery operations in the southeastern US. Presence of allelochemicals in water eluates of woodchips and leaves was evaluated in a lettuce bioassay. Eluates of wood chips from red maple (Acer rubrum L.), swamp chestnut oak (Quercus michauxii Nutt.), red cedar (Juniperus silicicola L.H. Bailey), neem (Azadirachta indica A. Juss.), and magnolia (Magnolia grandiflora L.) highly inhibited germinating lettuce seeds, as assessed by inhibition of hypocotyl and radicle growth. The effects of wood chip eluates from these five species were more than that found for eluates from wood chips of black walnut (Juglans nigra L.,) a species previously identified to have weed-suppressing allelochemicals. Tests on red cedar, red maple, and neem showed that water-soluble allelochemicals were present not only in the wood but also in the leaves. In greenhouse trials, red cedar wood chip mulch significantly inhibited the growth of florida beggarweed (Desmodium tortuosum DC.), compared to the gravel-mulched and no-mulch controls.
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Nursery growers estimate that they spend $500 to $4000/acre ($1235 to $9880/ha) of containers for manual removal of weeds, depending upon weed species being removed. Economic losses due to weed infestations have been estimated at about $7000/acre ($17,290/ha). Herbicide treated bark nuggets were found extremely effective for weed control in studies during 1998, regardless of whether oxyfluorfen, oryzalin, or isoxaben were applied to the bark. A study conducted in 2000 compared 24 treatments of novel nonchemical alternatives, conventional chemical practices and herbicide treated barks. Four of the best treatments were herbicide treated douglas fir bark, specifically, small [<1 inch (2.5 cm) length] douglas fir nuggets treated with oryzalin at the 1× rate, large (>1 inch length) douglas fir nuggets treated with oryzalin at the 0.5× rate, small douglas fir nuggets treated with oryzalin at the 0.5× rate and large douglas fir nuggets treated with flumioxazin at the 1× rate. The four bark treatments indicated above provided equivalent efficacy and phytotoxicity to Geodiscs. Penn Mulch and Wulpack provided poor weed control. Mori Weed Bag, a black polyethylene sleeve, and Enviro LIDs, a plastic lid provided less control than herbicide treated bark. Compared to the bark alone, herbicide treated bark provides a 1.8-fold increase in efficacy and a 2.8-fold extension in duration of efficacy. Compared to the herbicide alone, herbicide treated bark provides a 1.5-fold increase in efficacy and a 2.2-fold reduction in phytotoxicity. Of the innovative weed control products tested herbicide treated bark provided the most promising results. The data support that the bark nuggets are possibly acting as slow release carriers for the herbicides or reducing the leaching potential of the herbicides. Recent studies have indicated that the controlled release of herbicides using lignin as the matrix offers a promising alternative technology for weed control.
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An integrated approach to weed control in nursery containers is crucial if herbicide applications during the growing season are to be reduced. This experiment, conducted in 2002 and 2003 in Urbana, Ill., evaluated rice hulls, leaf-waste pellets, and pine bark as herbicide carriers for the preemergence herbicides oryzalin at 2 lb/acre a.i. and diuron at 1 lb/acre a.i. The efficacy of the treatments in controlling annual weeds and the phytotoxic effects of the treatments on the woody plant species were evaluated in separate completely randomized designs. For the efficacy experiment, no ornamental plants were present and containers were each seeded with a mixture of 1:1:1 (by volume) of annual bluegrass (Poa annua), common groundsel (Senecio vulgaris), and shepherd's purse (Capsella bursa-pastoris) immediately after treatment applications. For the phytotoxicity experiment, ‘Goldflame’ spirea (Spiraea japonica), ‘Hetz Midget’ american arborvitae (Thuja occidentalis), and ‘Snowmound’ nippon spirea (Spiraea nipponica) were evaluated. No weed seeds were sown in the phytotoxicity containers. Treatments for both experiments included spray applications of herbicides with water or with one of the organic mulches as a carrier or one of the mulches alone. Evaluations were done 45 and 120 days after treatment (DAT) in both years. The organic carriers with herbicide sprays gave efficacy visual ratings equivalent to water as a carrier for both herbicides. Phytotoxicity was not observed in the spirea species in either year. For ‘Hetz Midget’ american arborvitae in 2002, diuron with water had the highest visual phytotoxicity rating. Diuron phytotoxicity on the ‘Hetz Midget’ american arborvitae was alleviated when diuron was applied with any of the three mulches as a carrier. Pine bark treatments increased plant biomass for ‘Goldflame’ spirea in 2003, 45 DAT. At 120 DAT in 2002, pine bark gave increased plant biomass as compared with no organic mulch treatments for ‘Goldflame’ spirea. The study was conducted to ascertain whether the use of organic mulches as carriers could reduce phytotoxic effects of a herbicide on container-grown woody ornamentals, improve crop plant biomass, and act as a herbicide carrier for container-grown woody ornamentals.
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The processes of N mineralization and immobilization which can occur in agricultural soils during decomposition of plant residues are briefly reviewed in this paper. Results from different incubation studies have indicated that the amounts of N immobilized can be very important and that the intensity and kinetics of N immobilization and subsequent remineralization depend on the nature of plant residues and the type of decomposers associated. However, most of the available literature on these processes refer to incubations where large amounts of mineral N were present in soil. Incubations carried out at low mineral N concentrations have shown that the decomposition rate of plant residues is decreased but not stopped. The immobilization intensity, expressed per unit of mineralized C, is reduced and N remineralization is delayed. Nitrogen availability in soil can therefore strongly modify the MIT kinetics (mineralization-immobilization turnover) by a feed-back effect. The mineralization and immobilization kinetics have been determined in a two-years field experiment in bare soil with or without wheat straw. Mineralization in plots without straw seemed to be realistically predicted by accounting for variations in soil temperature and moisture. Immobilization associated with straw decomposition was clearly shown. It was increased markedly by the addition of mineral N throughout decomposition. It is concluded that mineral N availability is an important factor controlling plant residues decomposition under field conditions. A better prediction of the evolution of mineral N in soil may therefore require description and modelling of the respective localization of both organic matter and mineral N in soil aggregates.
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We discuss the dynamics of plant litter, the effects of litter on the chemical and physical environment, the direct and indirect effects of plant litter on plant populations and communities, and different adaptative traits that may be related to litter accumulation. The production of litter depends primarily on the site productivity, but other properties of the environment, as well as chance, may introduce important variation. The existence of time lags between the production of plant organs and their transformation into litter appears as a relevant character of litter dynamics seldom included in models. Herbivory, and other processes that destroy biomass or reduce productivity, may reduce the amount of litter produced. The destruction of litter encompasses a complex of interactions. The main processes, including physical and chemical degradation, consumption by invertebrates and decomposition, are differentially affected by the environment and by the physical and chemical characteristics of the litter itself. The relative importance of those processes varies among systems.
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Moisture is an important component to activate preemergence herbicides; however, this aspect had not been investigated in soilless substrate. The objective of this study was to evaluate the influence of pre-application moisture levels and post-application irrigation levels in the preemergence control of hairy bittercress with flumioxazin in a pine bark substrate. Three similar experiments were conducted over a 13-month period. Treatments were a factorial arrangement at the following variables: three pre-application moisture levels (dry, medium and wet), two flumioxazin formulations (granular and spray), two flumioxazin rates [0.28 and 0.42 kg ai·ha−1 (0.250 and 0.375 lb ai·A−1)] and four levels of single-event, post-application irrigation [0.6, 1.3, 2.5 and 5.1 cm (0.25, 0.50, 1.00 and 2.00 in)]. Treated pots were overseeded with 25 hairy bittercress at 1 week after flumioxazin application. Pre-application moisture did not affect the flumioxazin efficacy at any time and treatment. The spray formulation (SureGuard) provided maximum fresh weight control (≥ 99%) in weed counts up to 12 weeks after application, regardless of rate, pre-moisture level or post-irrigation level. The granular formulation (BroadStar) was less effective than spray formulation, and efficacy was improved with the higher rate and higher levels of post-application irrigation (Experiments 1 and 3).
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The market for large plants is increasing steadily; however, weed control in large containers present new production problems for growers. Experiments were conducted to evaluate pine bark mini-nuggets for weed control in 11 and 27 liter (#3 and #7) containers. In October 2004, Gardenia jasminoides (August Beauty gardenia) were seeded with oxalis, and Lagerstroemia indica ‘Natchez’ (crapemyrtle) with bittercress in 27 liter (#7) containers. In March 2005, Hydrangea quercifolia (oakleaf hydrangea) were seeded with oxalis and Ternstroemia gymnanthera (ternstroemia) with bittercress in 11 liter (#3) containers. Treatments consisted of mulch applied at depths of 0, 3.8, and 7.6 cm (0, 1.5 and 3.0 in), with seed applied either above or below the mulch. A separate group of treatments were included similar to the above except that a granular preemergence herbicide was applied after mulch application. Growth of crapemyrtle and ternstroemia were similar regardless of mulch depth. With gardenia and oakleaf hydrangea growth differences existed but there were no consistent trends among treatments. Season long weed control was obtained in all treatments that included 7.6 cm (3.0 in) mulch depth.
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Safer methods of herbicide application are needed for irregular planting areas. The herbicide 2,6-dichlorobenzonitrile (dichlobenil) was incorporated into various organic mulches so that a specified depth of mulch delivered the desired concentration of herbicide. The incorporation technique provided equal or better weed control than either the dichlobenil or mulch used alone. In addition, prolonged effect of the dichlobenil was realized into the second year when it was incorporated into the mulch. Increasing the mulch depth to 4 inches increased the weed control. A nutrient supplemented mulch in conjunction with the dichlobenil increased the growth of many woody ornamental plants as much as 300 to 400%.
Article
Two experiments were conducted at the The Ohio State University Waterman Farm, Columbus, on efficacy and phytotoxicity with evalautions at 30, 60, 90, and 120 DAT using dry weights and visual ratings 0–10 with >7 being commercially acceptable for efficacy, and 1–10 with <3 being commercially acceptable for phytotoxicity. The herbicide-treated mulches and herbicide–mulch application methods were compared to sprays of the five chemicals applied directly to the surfaces of the plots [oryzalin (oryzalin), (AS) Surflan (aqueous solution) 2 lb/acre (a.i.), flumioxazin (SureGuard WDG), 0.34 lb/acre (a.i.), acetochlor 76% (Harness 2.5 lb/acre (a.i.), dichlobenil (Casoron CS) 4 lb/acre (a.i.) and a combination of oryzalin and flumioxazin], two untreated mulches (pine and hardwood) and a weedy. Mulches were applied untreated, over the top of soil surfaces sprayed with the different herbicides. Mulches were also applied untreated to untreated soil surfaces and then sprayed with the different herbicides. Pretreated bark mulches were also evaluated and prepared by placing the mulches on a sheet of plastic, as a single layer thick and sprayed and allowed to dry for 48 hours. Twenty of 38 treatments gave efficacy rating of >7, pooled over all evaluation dates. One was a direct spray, Surflan + SureGuard (7.6). Three were pretreated mulches, Surflan + SureGuard (8.2), Harness (7.8) and Surflan (7.4) treated pine. None of the pretreated hardwood barks provided ratings of >7. Nine were treatments with the herbicides applied under the bark. Seven of the nine provided ratings of >8 and only one involved hardwood bark, Surflan + SureGuard under pine (9.1), Casoron under pine (8.9), Surflan under pine (8.7), Harness under pine (8.3), Harness under pine (8.0) and SureGuard under hardwood (8.0).
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Field experiments to compare the loss of oryzalin (3,5-dinitro- N⁴ , N⁴ -dipropylsulfanilamide) from straw-mulched and nonmulched soils indicated that oryzalin disappeared more rapidly in soils covered by straw in 1980 and 1981 but not in 1982. It appeared that greater rainfall in 1982 was responsible for this difference. Straw mulch on the soil at the time of application reduced the amount of oryzalin reaching the soil surface after subsequent rains or irrigation. Straw levels of 2250 or 4500 kg/ha, when present at the time of treatment, reduced oryzalin concentration in the soil by approximately 15 or 43%, respectively, following 1.3 cm of water applied by sprinkle irrigation. Increasing the straw levels above 4500 kg/ha did not significantly affect the amount of oryzalin detected in the soil beneath the straw mulch.
Article
Four organic mulches, screened pinebark, hardwood (primarily oak), cypress and decorative pinebark nuggets, applied at depths of 0, 5, 10, and 15 cm (0, 2, 4, 6 in) with or without an inorganic weed barrier fabric, were tested in field and container studies to determine their effect on weed suppression, soil pH, soil nitrogen content, and growth of Ligustrum japonicum. Results indicated that mulch applied at shallower depths, in combination with a weed barrier, provided optimal weed control without tying up soil nitrogen or reducing plant growth. Coarser mulches out-performed finer-textured materials. Most effective weed control was obtained with decorative pinebark nuggets with weed barrier fabric at a 15 cm (6 in) depth of application when compared to unmulched controls. As the depth of mulch was increased, soil pH, soil nitrogen content, and visual rating of plant growth decreased. Mulches over 10 cm (4 in) deep tended to inhibit plant growth, although optimum depth was dependent on the mulch material used.
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The practical aspects of nonwovens as a covering layer in conjunction with organic or inorganic mulching layers above or below are presented. Weed penetration occurs in several types of laying. There are 7 references.
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Granules of isoxaben plus trifluralin and liquid applications of isoxaben plus oryzalin were applied to miniature nursery plots covered with plastic, woven landscape fabric, or gravel with no cover. Herbicide concentrations were monitored in runoff water over a 30 d period. Runoff losses of isoxaben from the sprayable formulation applied to gravel were 5% greater than from plastic and 4% greater than losses from fabric in 1992. Similarly, oryzalin losses from the sprayable formulation applied to gravel were 7% greater than losses from plastic and 4% greater than losses from the fabric ground cover. In contrast, loss of isoxaben from the granular formulation applied to plastic was 7% greater than loss from gravel in 1993. Isoxaben losses from the granular formulation applied to fabric were intermediate. Trifluralin losses from the granular formulation applied to plastic and fabric were both 3% greater than losses from gravel. In addition, isoxaben losses from the granular formulation were 11 and 10% greater than loss from the sprayable formulation applied to the plastic and fabric-covered plots, respectively. Isoxaben losses from the sprayable formulation applied to gravel were 11% greater than losses from the granular formulation. In an experiment to determine herbicide release patterns and the effect of light on residues from the granular formulation of isoxaben and trifluralin in irrigation effluent, water was monitored for 36 d. Approximately 20% of the applied isoxaben and 7% of the applied trifluralin was detected in irrigation water during the 36 d period. These studies indicate that runoff losses and the ultimate fate of isoxaben, oryzalin, and trifluralin applied in nursery settings depend on factors including ground cover composition, herbicide formulation, and photochemical degradation.
Article
Research was conducted to determine the effect of winter wheat ( Triticum aestivum L.) straw mulch level on weed control in a winter wheat-ecofallow corn ( Zea mays L.)-fallow rotation at North Platte and Sidney, NE, in 1981 and 1982. Wheat straw mulch was established at 0, 1.7, 3.4, 5.1, and 6.8 Mg/ha in stubble fields. After application of 1.5 times the recommended rate at corn planting, metolachlor [2-chloro- N -(2-ethyl-6-methylphenyl)- N -(2-methoxy-1-methylethyl)acetamide] concentration remained higher in unmulched soil than in mulched soil for more than 4 months, due to interception of metolachlor by the mulch. Even though the amount of metolachlor in the soil was reduced by mulch, weed control was not reduced and increased with increasing mulch level. Thus, increasing metolachlor rate was not necessary to maintain adequate weed control in no-till winter wheat stubble since mulch itself provided some measure of weed control.
Article
Five organic mulches (pine bark, hardwood bark, cedar chips, longleaf pine needles, shortleaf pine needles), used alone or in combination with two inorganic mulches (black polyethylene, woven polypropylene), were evaluated over two years for weed control, durability, aesthetic value, and influence upon soil temperature. Organic mulches reduced total weed counts by 50% compared to control plots. and underlaying organic mulches with polyethylene resulted in complete control. Polypropylene, used in combination with organic mulch, was ineffective in controlling perennial weed species. Pine bark was the most durable organic mulch, requiring the least replenishment (70% initial volume) after 630 days. Durability of organic mulches increased when underlaid with polyethylene. Longleaf pine needles were rated most attractive, and underlying organic materials with either polyethylene or polypropylene enhanced appearance. Organic mulches reduced maximum daily temperatures at the soil surface by 2.2–3.3°C (4–6°F) and increased minimum daily temperatures by 1.1–2.2°C (2–4°F). However, the type of organic mulch did not affect temperatures at the soil surface.
Article
Recent changes in technology, governmental regulation and scrutiny, and public opinion have motivated the agricultural community to examine current management practices from the perspective of how they fit into a sustainable agricultural framework. One aspect which can be incorporated into many existing farming systems is plant residue management (e.g., reduced tillage, cover crops). Many residue management systems are designed to enhance accumulation of plant residue at the soil surface. The plant residue covering the soil surface provides many benefits, including protection from soil erosion, soil moisture conservation by acting as a barrier against evaporation, improved soil tilth, and inhibition of weed emergence. This review summarizes recent literature (ca. last 25 yr) concerning the effects of plant residue management on the soil environment and how those changes impact herbicide interactions.
Article
Field research was conducted at Hancock, WI, from 1985 through 1987 to evaluate effects of conventional tillage, chisel plow, ridge tillage, and no-tillage systems on population dynamics and control of annual weed species in corn grown continuously on a loamy sand soil without irrigation. In all years of the study, green foxtail densities were greater in chisel plow and no-tillage than in the conventional tillage system, while ridge tillage had densities lower than all other tillage systems. Common lambsquarters density in the chisel plow system reached nearly 500 plants m ⁻² compared to less than 75 plants m ⁻² in the other tillage systems when averaged over years. Average redroot pigweed densities in the no-tillage and chisel plow systems were 307 and 245 plants m ⁻² compared to less than 25 plants m ⁻² in the conventional and ridge tillage systems. Horseweed was observed only in no-tillage and ridge tillage plots. Green foxtail and redroot pigweed were more difficult to control in chisel plow and no-tillage than in the conventional and ridge tillage systems with several herbicide treatments. Corn yields were not affected by tillage systems under weed-free conditions. Corn yield differences among tillage systems when the same herbicide treatment was applied appeared to be due to differences in weed control.
Article
Acetochlor [2-chloro- N -(ethoxymethyl)- N -(2-ethyl-6-methylphenyl)acetamide], alachlor [2-chloro- N -(2,6-diethylphenyl)- N -(methoxymethyl)acetamide], and metolachlor [2-chloro- N -(2-ethyl-6-methylphenyl)- N -(2-methoxy-1-methylethyl)acetamide] were applied in 280 L of water/ha to plots covered with 0 to 6720 kg/ha of wheat ( Triticum aestivum L.) straw. At straw levels of 1120 kg/ha or greater, 50% or less of the applied herbicides were received by the soil surface before irrigation. Sprinkle irrigation (1.3 cm) washed 15 to 20% of the originally applied herbicide into the soil regardless of straw level. More metolachlor was retained on the straw than acetochlor or alachlor. Analysis of the wheat straw indicated that little water-extractable herbicide remained for all herbicides. Initial herbicidal activity on grain sorghum [ Sorghum bicolor (L.) Moench.] was reduced by the presence of wheat straw at the time of application, with acetochlor being least affected and alachlor most affected. Ten days after treatment, less than 10% of the original alachlor and acetochlor remained in the soil. When planted at this time, grain sorghum response was inversely related to the amount of straw mulch that was originally present. Metolachlor residues in the soil on day 10 were 11 to 26% of that on day 0 and there was comparably less reduction in activity on grain sorghum.
Article
The behavior and dissipation of 26 dinitroaniline herbicides in soils are reviewed. Some of the compounds also are referred to as dinitrotoluidines, -benzen(e)amines, -benzenediamines, -cumidines, -benzenesulfonamides, -acetophenones, and sulfonylsulfilimines. All dinitroanilines are sorbed to soil particles, particularly to organic or humic substances, and are nearly immobile in soils. Soil K values range from 7 to 117 and K OC values range from 80 to 471 000. Compounds with vapor pressures greater than 50 × 10 ⁻⁶ mm of Hg at ambient temperatures were reported to volatilize and diffuse through, and out of, the soil in significant amounts, depending on temperature and moisture conditions. Greater losses occurred from warm, moist soils than from cool, dry soils. Photodecomposition of dinitroanilines on soil surfaces was low but occurred when the chemicals were present in the vapor state or in aqueous solutions. Bioavailability of the chemicals decreased as organic matter contents of the soils increased. Dinitroaniline herbicides were degraded primarily by soil microorganisms, and fungi were the major organisms involved. Degradation proceeded faster under anaerobic conditions than under aerobic conditions and faster under warm, moist conditions than under cool, dry conditions. Half-life values for dinitroanilines ranged from 7 to 27 days under anaerobic conditions and from 19 to 132 days under aerobic conditions. The chemicals did not affect most soil microflora; and any significant effects reported were of short duration.
Article
Field experiments were conducted on six loam and sandy loam soils to study the influence of various soil parameters on atrazine, cyanazine, alachlor, metolachlor, and pendimethalin efficacy. Herbicidal activity was highly correlated to the soil organic content. Humic matter content was equally or better correlated (r = 0.70 to 0.91) with herbicide bioactivity than was organic matter content (r = 0.66 to 0.84). Regression equations were determined which allow herbicide rate recommendations for 80% weed control to be calculated based on soil humic matter or organic matter levels.
Article
Mulches on the soil surface are known to suppress weed emergence, but the quantitative relationships between emergence and mulch properties have not been clearly defined. A theoretical framework for describing the relationships among mulch mass, area index, height, cover, light extinction, and weed emergence is introduced. This theory is applied to data from experiments on emergence of four annual weed species through mulches of selected materials applied at six rates. Mulch materials, in order from lowest to highest surface-area-to-mass ratio, were bark chips, Zea mays stalks, Secale cereale, Trifolium incarnatum, Vicia villosa, Quercus leaves, and landscape fabric strips. The order of weed species' sensitivity to mulches was Amaranthus retroflexus > Chenopodium album > Setaria faberi > Abutilon theophrasti, regardless of mulch material. The success of emergence through mulches was related to the capacity of seedlings to grow around obstructing mulch elements under limiting light conditions. Mulch area index was a pivotal property for quantitatively defining mulch properties and understanding weed emergence through mulches. A two-parameter model of emergence as a function of mulch area index and fraction of mulch volume that was solid reasonably predicted emergence across the range of mulches investigated.
Article
Dark dormancy prevents germination of seeds in the soil, which could otherwise be fatal, but seeds may not be dark dormant upon dispersal, or exposure, to stimulatory doses of light before burial may still cause the seeds to germinate in the soil. In Origanum vulgare dark dormancy was re-established rather slowly. Disappeareance of phytochrome in the far-red absorbing form (Pfr) and re-establishment of phytochrome control, from which the seeds had escaped, were involved. Induction of dark dormancy was much faster in Plantago major due to a reduction in responsiveness to light, absence of escape from phytochrome control and a high threshold level of Pfr for breaking dormancy. Not all seeds of O. vulgare and P. lanceolata were initially dark dormant; a light requirement was induced in the former, but not in c25% of the seeds of the latter species. -from Author
Article
(1) An attempt has been made to relate the temporal pattern of seed germination in Senecio and Capsella to environmental conditions. This has been based on an examination of the germination of populations of seeds in the field in relation to records of environmental variables which previous laboratory investigations had shown to influence germination. (2) Most Capsella seeds show a pronounced innate dormancy which is removed by a period of cold treatment on the imbibed seeds (stratification). One winter period fulfils the requirements of most seeds, but others require two winter periods. Seasonal increases in nitrate combined with fluctuating temperatures, which can replace the stratification requirements of many seeds, may also be important in removing innate dormancy. After cold treatment the germination of most seeds will take place only if exposed to light; in other words, only if the seeds are at the soil surface. (3) Senecio seeds do not show a stratification requirement and show less initial innate dormancy than Capsella. The number of seeds showing innate dormancy varies with the season of maturation: few seeds collected in the summer show innate dormancy as compared with samples collected at other times of the year. All innate dormancy disappears after about 6 months' burial in the soil. The majority of Senecio seeds also require light for germination, though the proportion capable of germinating in the dark is greater than for Capsella, and this proportion is increased as the germination temperature is lowered to around 10° C. Consequently, it was found that initially more buried seeds of Senecio were capable of emerging than those of Capsella. (4) When buried in the soil, although innate dormancy may have disappeared, dormancy is enforced on almost the entire population of both species mainly by lack of light, though there is evidence that other factors, probably raised CO2 and lowered O2 levels, may contribute to this effect. The inhibition of germination is removed immediately if the seeds are placed in light in a normal atmosphere. (5) Germination of field populations occurs in flushes; the dates of the flushes vary from year to year but are coincident in the two species at the same sites. The first flush which usually occurs in February or March, appears to be related to the rise in soil temperature to about 10° C. Analysis of the factors causing later flushes is somewhat speculative but the results suggest that warm dry conditions followed by rain are stimulatory. An additional factor, in Capsella at least, may be high soil nitrate levels acting synergistically with large diurnal fluctuations of temperature.
Article
Yellow nutsedge (Cyperus esculentus) is one of the most troublesome and widespread perennial weeds infesting landscape plantings in the United States. Few selective herbicides are available for managing this weed. A combination of organic mulch with preemergence herbicide may improve control efficacy at tuber emergence and reduce the need for subsequent postemergence applications. However, limited information is available on potential interactions between herbicide placement and mulching and their effect on yellow nutsedge control and landscape plant growth and quality. In this study, control efficacy of preemergence herbicide s-ethyl dipropylthiocarbamate (EPTC) applied at 0, 4, or 6 lb/acre above or under pine straw, pine nuggets, or shredded cypress mulches were evaluated in landscape beds infested with yellow nutsedge and planted with 'Mystery' gardenia (Gardenia jasminoides), 'Stella de Oro' daylily (Hemerocallis), and 'Big Blue' liriope (Liriope muscari). Pine nuggets provided greater yellow nutsedge control compared with shredded cypress during the first 6 weeks after treatment (WAT) in mulch-alone plots. All mulch-alone plots had similar yellow nutsedge shoot densities and were 40% to 60% less than untreated bare soil plots from 6 to 12 WAT. Control efficacy was greater when EPTC was applied under mulch compared with above-mulch applications regardless of mulch products. In addition, EPTC at low rate resulted in similar control as high rate when applied under mulch. No injury was observed on any ornamental plants treated with EPTC. Mulching improved growth, flowering, and overall visual quality of gardenia, but reduced number of flowers in daylily and aboveground biomass in liriope at some sample dates though their visual qualities were unaffected. Based on these preliminary data, EPTC applied preemergence before mulching a new landscape bed or replenishing an existing bed can improve yellow nutsedge control without injuring selected ornamental plants.
Article
Resumen Se realizaron estudios en un invernadero para determinar la interacción de los residuos del arroz como cobertura (0, 3 y 6 t ha−1) y herbicidas (testigo no-tratado, oxadiazon a 0.5 y 1.0 kg ai ha−1, y pendimethalin a 1.0 y 2.0 kg ai ha−1) sobre la emergencia de plántulas y la biomasa de Echinochloa crus-galli, Dactyloctenium aegyptium, Echinochloa colona y Cyperus iria. Sin importar la cantidad de cobertura, D. aegyptium y E. colona fueron controladas efectivamente por todos los tratamientos de herbicidas. Ninguna plántula de estas especies de malezas escaparon a los herbicidas cuando se aplicó en presencia de la cobertura con residuos de arroz. No hubo sobrevivencia de plántulas de E. crus-galli, cuando ambos herbicidas se aplicaron sobre suelo desnudo (sin cobertura de residuos); sin embargo, algunas plántulas sobrevivieron a oxadiazon y pendimethalin cuando estos se aplicaron en presencia de la cobertura de residuos. Para C. iria, las aplicaciones de herbicidas en presencia de la cobertura resultó en menor control que en la ausencia de residuos. Estos resultados sugieren que algunas especies de malezas pueden escapar a las aplicaciones de herbicidas PRE en sistemas de agricultura de conservación en los cuales los herbicidas aplicados al suelo pueden adherirse a los residuos disminuyendo su eficacia.
Article
Strategies for utilizing allelopathy as an aid in crop production include both avoidance and application protocols. There are immediate opportunities for management of weed and crop residues, tillage practices, and crop sequences to minimize crop losses from allelopathy and also to use allelopathic crops for weed control. Varieties of grain and forage sorghums (Sorghum Spp.), sunflower (Helianthus annuus L.), oats (Avena sativa L.), wheat (Triticum sativum L.),rye (Secale cereale L.), and others may provide weed control and in some instances crop stimulation from their residues. Our four-year field study with cultivated sunflower resulted in no differences in weed biomass between plots with and without herbicide (EPTC) applications. Strip cropping that included sorghum showed that in the subsequent year weed density and biomass were significantly lower in the previous-year sorghum than in soybean strips. Possibilities exist for modification of crop plant metabolism to alter production of allelochemicals. Allelochemical-environmental interactions must be considered in efforts to benefit from allelopathy. Under greenhouse conditions, joint application of low levels of atrazine, trifluralin, alachlor, or cinmethylin with a phenolic allelochemical showed that these two categories of inhibitors acted in concert to reduce plant growth. Allelochemicals may also be adapted as yield stimulants or environmentally sound herbicides, such as cinmethylin and methoxyphenone. Isolation of bialophos, tentoxin, and others shows that bacteria and fungi are good sources of biologically active compounds.
Article
Many of the organic chemicals used in agricultural production are susceptible to loss from the soil surface to the atmosphere by volatilization. Adequate prediction of the impact of these chemicals on the environment thus requires consideration of both downward movement through the soil to groundwater and upward movement in the gas phase to the atmosphere. We developed a method to mechanistically simulate volatilization within the framework of a conventionally formulated solute transport model and used it to simulate the gas-phase losses of EPTC, a commonly used volatile herbicide. The model considers efflux of a trace gas at the sod surface to be a process of unsteady diffusion, interrupted intermittently by dispersive events that can be thought of as eddies at the innermost scale. Model results were compared to measurements of volatilization during the first 7 d following application of EPTC, conducted with a Bowen ratio system in a 17-ha field at Rosemount, MN. The measurements indicated a relatively large initial flux (ca. 150 g ha⁻¹ h⁻¹) that rapidly decreased to negligible levels within a day following application. The model agreed reasonably well on the first day, if a measured value for Henry`s constant was used rather than a value estimated from the saturation vapor pressure and the solubility. However, on subsequent days the model considerably overestimated volatilization, regardless of the Henry`s constant that was used. It is likely that hysteresis in sorption/desorption, particularly as surface soil dries following herbicide incorporation, may be the primary reason why volatile losses are lower than might be predicted on the basis of equilibrium partitioning theory. 42 refs., 5 figs., 1 tab.
Article
The concentrations and loads of atrazine in runoff water from tilted-bed soil trays under intense simulated rainfall were similar to losses reported in field studies. -from Author
Article
Biorational alternatives are gaining increased attention for weed control because of concerns related to pesticide usage and dwindling numbers of labeled products, particularly for minor-use crops. Allelopathy offers potential for biorational weed control through the production and release of allelochemics from leaves, flowers, seeds, stems, and roots of living or decomposing plant materials. Under appropriate conditions, allelochemics may be released in quantities suppressive to developing weed seedlings. Allelochemics often exhibit selectivity, similar to synthetic herbicides. Two main approaches have been investigated for allelopathic weed suppression. One is use of living rotational crops or mulches that interfere with the growth of surrounding weeds [e.g., tall red rescue, Festuca arundinacea Schreb.; creeping red rescue, F. rubra L. subsp. commutata; asparagus. Asparagus officinalis L. var. altilis); sorghum, Sorghum bicolor (L.) Moench; alfalfa, Medicago sativa L.; black mustard, Brassica nigra (L.) Koch; and oat, Avena saliva L.]. Attempts to select germplasm with enhanced suppressive ability have been limited. The second is use of cover crop residues or living mulches to suppress weed growth for variable lengths of time (e.g., winter rye, Secale cereale L.; winter wheat, Triticum aestivum L.; and sorghum). Cover crop residues may selectively provide weed suppression through their physical presence on the soil surface and by release of allelochemics or microbially altered allelochemics. The ability to understand the physiological basis for allelopathy in a crop plant may allow the weed scientist or ecologist to work closely with molecular biologists or traditional plant breeders to selectively enhance the traits responsible for weed suppression.
Article
The classification of herbicides by site of action, published in 1997, has been revised. The classification system uses a numbering system for a herbicide's site of action, chemical family, and common name. Regulatory agencies in the United States and Canada have published labeling guidelines based on the classification to aid in herbicide resistance management. Abbreviations: EPA, Environmental Protection Agency; HRAC, Herbicide Resistance Action Committee; PMRA, Pest Management Regulatory Agency.
Article
The ease of ignition of 13 commonly used landscape mulches was evaluated. Mulches have different ignition potentials based on several factors, including the length of exposure to heat and to the ignition source. Some materials ignited more frequently when exposed to a lit propane torch for 15 seconds. The most to least commonly ignited materials were ground rubber, pine straw, oat straw, shredded hardwood bark, shredded cypress bark, recycled pallets, 2.5 to 5 cm pine bark nuggets, 1.3 to 2.5 cm pine bark nuggets, shredded pine bark, cocoa shells, composted yard waste, bluegrass sod, and brick chips. Not all organic mulches readily ignited, nor were inorganic mulches uniformly ignition resistant. The results of this research show that there are definite differences in the ease of ignition between commonly used mulches. The results demonstrate that landscapers do not have to resort to using inorganic materials such as brick chips and gravel for ignition-resistant mulches. Under high-temperature ignition, one inorganic material, ground rubber was ignited consistently and was difficult to extinguish. Conversely, there are organic materials that are unlikely to ignite. These also are maintenance practices that will prevent or reduce ignition of these mulches.
Article
This study compared chemical, allelopathic, and decomposition properties of 6 mulches: cypress, eu- calyptus, pine bark, pine needle, melaleuca, and a utility- trimming mulch (GRU). Eucalyptus and GRU mulches had the highest decomposition after 1 year (21% and 32%), while only 3% to 7 % of the other mulches de- cayed. Lignin and lignin:nitrogen ratio were negatively correlated with decomposition; high values resulted in low decomposition. Winter respiration of both eucalyptus and GRU mulches was high, and respiration was posi- tively correlated with decomposition. Pine-straw mulch subsided from 9 cm (3.5 in.) to 4 cm (1.6 in.) during the year, while the other mulches subsided approximately 2 cm (0.8 in). Nutrient composition of the mulches was sig- nificantly different, with GRU mulch having the highest levels of calcium (Ca), magnesium (Mg), nitrogen (N), phosphorus (P), and potassium (K). Pine straw was the next highest in N and P. Soils under the mulches were acidified most by pine straw (from a pH of 5.0 to 4.4), followed by pine bark and cypress. In a standard test of allelopathy, all fresh mulches inhibited germination of let- tuce seed, and although variable in concentration , all mulches contained hydroxylated aromatic compounds that could have caused these allelopathic effects. After 9 months and 1 year, pine straw and GRU still exhibited allelopathic effects on germination. Cypress, melaleuca, and pine bark retained their color after 1 year, while the other 3 mulches changed to a pinkish gray.
Article
IT is well known that the upper layers of many types of soil contain large populations of buried, dormant seeds estimated to amount to many thousands per acre in some instances1. Many of these buried seeds are viable and germinate readily when the soil is cultivated or disturbed in other ways. There is good evidence that such seeds can remain dormant in the soil for long periods; indeed, evidence has recently been presented that seeds which have lain in the soil for as much as 1,700 years are still viable2.
Article
The process of labeling new herbicides for specialty crops has always been difficult. Progress in solving specialty crop weed control problems will likely be more challenging in the future. Major crops like corn, cotton, rice, soybean, and wheat are planted on millions of hectares, and most of these crops are treated with herbicides. In contrast, specialty crops (i.e., minor crops, e.g., container ornamentals or lettuce) are planted on 122,000 ha or less; thus, the potential value of herbicide sales is limited in these crops by the low number of hectares planted per crop. High crop value, small hectarage per crop, and generally marginal herbicide selectivity results in a high potential of liability for herbicide registrants and little incentive to label herbicides in these crops. The Interregional Project Number 4 (IR-4) program facilitates the registrations of pesticides on minor crops. Work needed to support pesticide tolerance in a given crop is conducted by IR-4 and cooperators. However, to develop new crop tolerances, the IR-4 process requires new herbicides. The success of glyphosate-resistant soybean has resulted in a less profitable herbicide market for all crops. In response, most primary pesticide manufacturers have reduced the size, or even eliminated herbicide discovery programs. As private industry slows or stops herbicide development, there will be fewer new minor-crop herbicides. Many questions face minor-crop weed scientists. For example, what are other practical solutions to control weeds in minor crops besides herbicides? Should research focus on development of competition models and decision thresholds or on weed removal tools such as robotics? What funding sources are available for minor-crop weed scientists? Are grant programs at the Federal level prepared to increase support for minor-crop weed research? Will university administrators replace retiring specialty crop weed scientists, knowing that their funding sources will produce little overhead? These questions require a response from all parties interested in specialty crop weed control. Nomenclature: Corn, Zea mays L., cotton, Gossypium hirsutum L., lettuce, Lactuca sativa L., rice, Oryza sativa L., soybean, Glycine max (L.) Merr.; wheat, Triticum aestivum L.
Article
Mulches on the soil surface are known to suppress weed emergence, but the quantitative relationships between emergence and mulch properties have not been clearly defined. A theoretical framework for describing the relationships among mulch mass, area index, height, cover, light extinction, and weed emergence is introduced. This theory is applied to data from experiments on emergence of four annual weed species through mulches of selected materials applied at six rates. Mulch materials, in order from lowest to highest surface-area-to-mass ratio, were bark chips, Zea mays stalks, Secale cereale, Trifolium incarnatum, Vicia villosa, Quercus leaves, and landscape fabric strips. The order of weed species' sensitivity to mulches was Amaranthus retroflexus > Chenopodium album > Setaria faberi > Abutilon theophrasti, regardless of mulch material. The success of emergence through mulches was related to the capacity of seedlings to grow around obstructing mulch elements under limiting light conditions. Mulch area index was a pivotal property for quantitatively defining mulch properties and understanding weed emergence through mulches. A two-parameter model of emergence as a function of mulch area index and fraction of mulch volume that was solid reasonably predicted emergence across the range of mulches investigated. Nomenclature: Abutilon theophrasti Medicus ABUTH, velvetleaf; Amaranthus retroflexus L. AMARE, redroot pigweed; Chenopodium album L. CHEAL, common lambsquarters; Setaria faberi Herrm. SETFA, giant foxtail; Quercus alba L., white oak; Quercus montana Willd., chestnut oak; Secale cereale L., rye; Trifolium incarnatum L., crimson clover; Vicia villosa Roth, hairy vetch; Zea mays L., corn.
Article
European legislation concerning ground- and surface-water quality and the protection of non-target organisms in surface-water from pesticide contamination has initiated more stringent data requirements from regulatory authorities concerning the movement of all pesticides in soils. Other interested parties, such as water companies, environment agencies and consumer-driven organizations, have sought to influence the use of herbicides and their impact on the environment. The resulting studies and associated research have led to a better understanding of the fate and behaviour of herbicides in the soil environment. The amount of herbicide that moves away from the area of application will depend on the physico-chemical properties of the chemical and the agroclimatic characteristics of the target site. Under average conditions, the amount of herbicide lost by movement from a soil profile is typically <0.1% to 1% of the applied mass but, under certain localized circumstances, can reach up to 5% or greater. Leaching, drain-flow and surface run-off are the main pathways responsible for herbicide movement within soils. The soil/herbicide processes determining the losses are also variable in both time and space. It is therefore necessary to understand the spatial characteristics of soils, their hydrology and the associated herbicide use patterns.
Article
The use of allelopathic cover crops in reduced tillage cropping systems may provide an ecologically sound and environmentally safe management strategy for weed control. Growers often plant winter rye (Secale cereale L.) for increased soil organic matter and soil protection. Spring-planted living rye reduced weed biomass by 93% over plots without rye. Residues of fall-planted/spring-killed rye reduced total weed biomass over bare-ground controls. Rye residues also reduced total weed biomass by 63% when poplar excelsior was used as a control for the mulch effect, suggesting that allelopathy, in addition to the physical effects of the mulch, did contribute to weed control in these systems. In greenhouse studies, rye root leachates reduced tomato dry weight by 25–30%, which is additional evidence that rye is allelopathic to other plant species.
Article
Over half of the hired workers employed on U.S. crop farms have been unauthorized to work since the mid-1990s, thereby increasing risk for employers if increased immigration law enforcement reduces the availability and raises the cost of farm labor. Immigration reform that legalizes farm workers could speed exits from the farm workforce, thus putting upward pressure on farm wages. Better enforcement of existing immigration laws would reduce the supply of farm workers, also putting upward pressure on wages. Producer response to higher wages depends, in part, on the availability of guest workers and alternatives to hand labor such as labor-saving machinery.
Article
In order to determine whether shredded rubber mulches (RM) pose water quality risks when used in stormwater best management practices (BMPs) such as bioretention basins, batch leaching tests were conducted to identify and quantify constituents in leachates from RM such as metal ions, nutrients, total organic carbon (TOC), and aryl hydrocarbon receptor (AhR) activity (determined by the chemically activated luciferase gene expression (CALUX) bioassay) at varied temperature and initial pH values. The results indicate that aqueous extracts of RM contain high concentrations of zinc (Zn) compared with wood mulches (WM), and its concentration increased at lower pH and higher temperature. Although methanol extracts of RM displayed high AhR activity, none of the aqueous extracts of RM had significant activity. Hence, while unknown constituents that have significant AhR activity are present in RM, they appear to be not measurably extracted by water under environmental conditions relevant for stormwater (5<pH<9, 10<T<40 degrees C). Our results suggest that organic constituents in water extracts of RM which have AhR activity may not be of significant concern while leaching of Zn from RM appears to be a potentially larger water quality issue for RM.
Article
Photodegradation of the herbicide EPTC (S-ethyl-N, N-dipropylthiocarbamate), and the safener dichlormid (2,2-dichloro-N, N-diallylacetamide) has been examined in methanol and in water solutions. Irradiation of EPTC and dichlormid with UV light at 254 nm caused rapid degradation in both media. Remarkable and gradual changes in color of EPTC irradiated solution was observed from clear to yellow then to intense orange. EPTC half-life of elimination in water was 14.0, and 18.5 min, and in methanol 37.2 and 32.2 min, when irradiated with and without dichlormid, respectively. There was significant difference between rate of EPTC degradation in water and methanol in the presence or in the absence of dichlormid. Negligible degradation of EPTC or dichlormid at > 290 nm was observed. Photoproducts were separated and identified using GC or/and thin-layer chromatography then identified using mass spectrometry. It appeared that some products have high molecular weight that formed as a result of dimerization. This is possibly a result of the coupling of radicals that formed through EPTC degradation. The cleavage of C-S and C-N bonds accounted for the formation of these radicals. Gradual dealkylation of the acid chains of EPTC has also occurred. EPTC-sulfoxide, EPTC-sulfone, Propylamine and dipropylamine were detected as photoproducts of EPTC at 254 nm. Dichlormid pathways of degradation at 254 nm were characterized as dechlorination, dealkylation, and hydrolysis both in water and methanol. The findings showed that dichlormid did not significantly affect EPTC photodegradation either at 254 nm or at > 290 nm. The biological/toxicological properties of the photoproducts need further study, particularly the dimer compounds.