bluuebunny/crossref_metadata_2025 huggingface dataset:
Managing Canada Thistle (Cirsium arvense) in a Constructed Grassland with Aminopyralid and Prescribed Fire
Authors: Gramig Greta G. , Ganguli Amy C.
Published: March 2015

Green spaces such as golf courses that intermingle within or exist on fringes of urban landscapes can provide opportunities for increasing the ecological value of urban areas. To that end, more naturalistic and less input-intensive “links”-style golf courses have recently gained favor over input-intensive parkland courses. The Osgood Public Golf Course in Fargo, ND is a links-style golf course set adjacent to suburban housing developments. This course incorporated large areas of prairie plantings, or “constructed grasslands,” which over time became dominated by fescue species and infested with Canada thistle. Our objective was to explore the efficacy of using prescribed fire combined with aminopyralid herbicide to control Canada thistle and promote a more diverse mix of warm-season C4 and cool-season C3 grasses. Aminopyralid was applied during fall 2010 and prescribed fire was applied during spring 2011. We found that aminopyralid provided excellent control of Canada thistle 1 and 2 yr post-treatment. Open niches created from Canada thistle control were readily filled by C3 grasses, primarily fescue species, which were the dominant species on the constructed grasslands prior to treatment. Fire intensity was variable within and across plots and was associated with reductions of litter and C3 grasses, but was not associated with increases of C4 grasses within the time frame of this study. Our results demonstrate the effectiveness of aminopyralid for Canada thistle control in constructed grasslands. Prescribed fire maintained C3 grass dominance while removing litter, but C4 grass response was variable and appeared dependent on pretreatment C4 species abundance. Reduction of litter in constructed grasslands dominated by fescue could potentially lead to microsite conditions that would favor C4 and other C3 species, especially if short-term management promoted additional facilitation efforts, such as repeat spring fire treatments and seeding.
Effect of Nitrogen Application, Rice Planting Density, and Water Regime on the Morphological Plasticity and Biomass Partitioning of Chinese Sprangletop (Leptochloa chinensis)
Authors: Awan Tahir Hussain , Sta. Cruz Pompe C. , Ahmed Sharif , Chauhan Bhagirath Singh
Published: March 2015

Due to the looming water and labor crisis, farmers are adopting dry-seeded rice establishment, in which Chinese sprangletop is becoming a major weed. Concerns about the excessive use of herbicides in controlling Chinese sprangletop highlight the need for cultural weed management strategies. Such strategies require an adequate understanding of Chinese sprangletop response to rice plant density, nutrition, and water regime. Therefore, a greenhouse study was conducted to determine the effect of water regime (aerobic and saturated), nitrogen (N) fertilization (50 and 150 kg ha−1), and rice density (0, 160, and 640 plants m−2) on the growth and reproduction of Chinese sprangletop. Chinese sprangletop plants were taller than rice in aerobic conditions than in saturated conditions. All growth parameters (shoot, root, and inflorescence biomass and leaf area, leaf weight, and inflorescence weight ratio) of Chinese sprangletop were higher in aerobic conditions than in saturated conditions when grown without rice. However, no difference was observed for these parameters between water regimes when Chinese sprangletop was grown with rice. Chinese sprangletop growth and seed production was not affected, but rice growth was affected by N rates. Irrespective of N rate and water regime, Chinese sprangletop height (34 to 59%), tiller number (87 to 92%), leaf number (83 to 89%), shoot biomass (93 to 99%), and inflorescence biomass (95 to 99%) decreased as rice density increased from 0 to 640 plants m−2. The ability of Chinese sprangletop to grow taller and produce more plant biomass (107%) and inflorescence biomass (183%) under aerobic than saturated conditions suggests the need for integrated weed management strategies for controlling weeds under water-limited environments. Such strategies might include the use of weed-competitive and drought-tolerant rice cultivars, high seeding rates, and optimum rate of fertilizer application.
Molecular Basis for Resistance to Fenoxaprop in Shortawn Foxtail (Alopecurus aequalis) from China
Authors: Guo Wenlei , Liu Weitang , Li Lingxu , Yuan Guohui , Du Long , Wang Jinxin
Published: March 2015

Shortawn foxtail is a competitive annual grass weed widely spread in east, south-central, and southwest China and parts of the Yellow River basin. One shortawn foxtail population (JSQT-1) resistant to fenoxaprop was identified in Jiangyan, Jiangsu province. Whole-plant experiments determined that the resistant population conferred high-level resistance to fenoxaprop (93-fold), clodinafop (21-fold), sethoxydim (107-fold), mesosulfuron (41-fold), and pyroxsulam (12-fold); moderate-level resistance to haloxyfop (8-fold), clethodim (9-fold), and pinoxaden (8-fold), and no resistance to isoproturon. Molecular analyses confirmed that the Ile-1781-Leu mutation was present in the resistant population. A dCAPS marker was used to detect the Ile-1781-Leu mutation. All 97 plants of the resistant population analyzed were homozygous mutants at the 1781 position. Our study established the first case of fenoxaprop resistance in shortawn foxtail, determined cross resistance to other herbicides, and elucidated that the molecular basis of resistance resulted from, at least partly, an Ile to Leu mutation at amino acid position 1781 in the plastid ACCase.
Tillage and Planting Date Effects on Weed Dormancy, Emergence, and Early Growth in Organic Corn
Authors: Teasdale John R. , Mirsky Steven B.
Published: March 2015

Insufficient weed control is a major constraint to adoption of reduced-tillage practices for organic grain production. Tillage, cover crop management, and crop planting date are factors that influence emergence periodicity and growth potential of important weed species in these systems. We assessed two hairy vetch cover crop management practices, disk-kill and roll-kill, across a range of corn planting dates from early May to late June in three experiments in Beltsville, MD. Patterns of seed dormancy, emergence, and early weed growth were determined for overseeded populations of common ragweed, giant foxtail, and smooth pigweed, three important species in the Mid-Atlantic states that represent early to late emergence. Common ragweed emergence was lowest and dormancy was highest of the three species across all planting dates. Giant foxtail emergence was higher than the other species in roll-killed hairy vetch and included a significant number of seeds that germinated before rolling operations in late June. Smooth pigweed had the highest emergence and lowest dormancy in disk-killed hairy vetch in June. Individual giant foxtail plant weight was higher in roll-killed than disk-killed hairy vetch in 2 of 3 yr, whereas that of smooth pigweed plants was higher in disk-killed than roll-killed vetch in 2 of 3 yr. Giant foxtail was the dominant species in roll-killed hairy vetch (averaged 79% of total weed biomass at corn silking), probably because of early germination and establishment before rolling operations. Smooth pigweed was the dominant species in disk-killed hairy vetch at June planting dates (averaged 77% of total weed biomass), probably because of high growth rates under warm conditions in tilled soil. This research demonstrated that cover crop management practices and the timing of planting operations can shift the dominant species of weed communities in organic farming systems and must be considered in long-term weed management planning.
Comparative Phytotoxicity Assays of the Herbicide Alloxydim and Its Main Identified Photoproduct in Cereal and Broadleaves Crops
Authors: Sandín-España Pilar , Sevilla-Morán Beatriz , Villarroya-Ferruz Mercedes , Alonso-Prados José L. , Santín-Montanyá M. Inés
Published: March 2015

When herbicides are sprayed in the field, a proportion of the herbicide falls onto leaves and soil surfaces, where it can be exposed to sunlight, generating photoproducts that can be more toxic and/or persistent than the parent substance and affect human health and the environment. The aim of this study was to identify the photoproducts of the herbicide alloxydim in leaf and soil model systems and to perform phytotoxicity studies. Alloxydim was rapidly photodegraded in systems simulating plant cuticles and soil surfaces, with half-lives ranging from 1 to 30 min. The main by-product, identified by LC-Qtof-MS as deallyoxylated alloxydim, was more stable than the active substance. The EC50values on root lengths of different varieties of wheat plants and one grass weed ranged from 0.38 to 0.50 mg L−1for alloxydim. In contrast, the EC50values for deallyoxylated alloxydim ranged from 94 to 600 mg L−1in the same species and in crops where the herbicide was applied. Special attention should be given to alloxydim degradation products because of the rapid degradation of this herbicide. Comparative bioassay studies between alloxydim and its photostable by-product showed that the by-product presents low phytotoxicity, whereas alloxydim can cause injury to neighboring and succeeding cereal crops.
Postemergence Herbicide Tolerance Variation in Peanut Germplasm
Authors: Leon Ramon G. , Tillman Barry L.
Published: March 2015

Although herbicide tolerance is not usually evaluated until the final stages of breeding programs, this trait is very important for grower adoption of new peanut cultivars. Understanding herbicide tolerance of breeding lines could help breeders develop selection strategies that maximize herbicide tolerance in new commercial cultivars. However, little is known about herbicide tolerance variability in peanut germplasm. Thirty-five randomly selected breeding lines from the peanut mini-core collection and cultivars ‘Florida-07’ and ‘Georgia-06G’ were evaluated for tolerance to 11 herbicides under greenhouse conditions. Variation among peanut lines in herbicide tolerance, measured as dry weight reductions (DWR), was similar across herbicides and was normally distributed. Florida-07 and Georgia-06G were in the lower two quartiles of injury and DWR among the evaluated peanut lines. Dose–response experiments showed that the most tolerant breeding lines had I50(the rate required to cause 50% injury) and GR50(the rate required to reduce dry weight 50%) values 0.4 to 2.5 times higher than the most susceptible lines, depending on the herbicide. A breeding line had a dicamba GR5013 times higher than the most susceptible line and 2.8 and 4.7 times higher than Florida-07 and Georgia-06G, respectively. The most tolerant lines were consistently tolerant to herbicides with different mechanisms of action, suggesting that nontarget site mechanisms are more likely to be responsible for the tolerance than target-site mutations. These results confirmed peanut-breeding programs would greatly benefit from screening breeding lines for tolerance to key herbicides and developing an herbicide-tolerance catalog. This information can be used when designing new crosses to reduce the risk of developing cultivars with low herbicide tolerance especially considering that one-half of the breeding lines exhibited lower tolerance than the commercial cultivars.
Target-Site Point Mutations Conferring Resistance to ACCase-Inhibiting Herbicides in Smooth Barley (Hordeum glaucum) and Hare Barley (Hordeum leporinum)
Authors: Shergill Lovreet S. , Malone Jenna , Boutsalis Peter , Preston Christopher , Gill Gurjeet
Published: March 2015

Acetyl coenzyme A carboxylase (ACCase)-inhibiting herbicides affect fatty acid biosynthesis in plants and are widely used to control smooth and hare barley in dicot crops in Australia. Recently, growers have experienced difficulty in controlling smooth and hare barley with herbicides from this mode of action. Dose–response experiments conducted on five suspected resistant populations confirmed varying levels of resistance to quizalofop and haloxyfop. The level of resistance in these populations was greater than 27-fold to quizalofop and greater than 15-fold to haloxyfop. The quizalofop dose required to reduce shoot biomass by 50% (GR50) for the resistant populations varied from 52.6 to 111.9 g ha−1, and for haloxyfop from 26.5 to 71.3 g ha−1. Sequencing the CT domain of the ACCase gene from resistant plants of different populations confirmed the presence of previously known mutations Ile1781Leu and Gly2096Ala. Amino acid substitution at the 2096 position conferred a greater level of resistance to haloxyfop than the substitution at the 1781 position. This study documents the first known case of field-evolved target-site resistance to ACCase-inhibiting herbicides in Australian populations of smooth barley.
Germination of Spotted Spurge (Chamaesyce maculata) Seeds in Response to Different Environmental Factors
Authors: Asgarpour Rayhaneh , Ghorbani Reza , Khajeh-Hosseini Mohammad , Mohammadvand Elmira , Chauhan Bhagirath Singh
Published: March 2015

Spotted spurge, a C4species, is a summer annual weed, introduced to the Golestan province of Iran in 2006. A series of laboratory experiments were conducted at the Faculty of Agriculture, Ferdowsi University of Mashhad, Iran, to evaluate the influence of environmental factors on seed germination of spotted spurge. Seeds germinated over a constant temperature range of 25 to 45 C with a 14-h photoperiod and at 30 to 50 C in continuous darkness. Seeds germinated at alternating day/night temperature regimes of 25/15 to 45/35 C, with maximum germination (> 80%) at alternating day/night temperatures of 35/25, 40/30, and 45/35C. Germination increased from 23.5 to 98% as water potential increased from −0.6 to 0 MPa (control). Germination was > 85% at sodium chloride (NaCl) concentrations up to 80 mM, with no germination at 160 mM NaCl. Germination was not affected by pH, and it was > more than 95% at pH ranging from 4 to 9. The germination of seeds submerged in water for a period less than 3 wk was > 60%, whereas no germination was observed after 9 wk of submergence in water. The results of our study could help to develop effective management strategies for this species. The results also suggest that spotted spurge could invade most tropical regions of Iran.
Influence of Herbicide Active Ingredient, Nozzle Type, Orifice Size, Spray Pressure, and Carrier Volume Rate on Spray Droplet Size Characteristics
Authors: Creech Cody F. , Henry Ryan S. , Fritz Bradley K. , Kruger Greg R.
Published: March 2015

Recent concerns regarding herbicide spray drift, its subsequent effect on the surrounding environment, and herbicide efficacy have prompted applicators to focus on methods to reduce off-target movement of herbicides. Herbicide applications are complex processes, and as such, few studies have been conducted that consider multiple variables that affect the droplet spectrum of herbicide sprays. The objective of this study was to evaluate the effects of nozzle type, orifice size, herbicide active ingredient, pressure, and carrier volume on the droplet spectra of the herbicide spray. Droplet spectrum data were collected on 720 combinations of spray-application variables, which included six spray solutions (five herbicides and water alone), four carrier volumes, five nozzles, two orifice sizes, and three operating pressures. The laboratory study was conducted using a Sympatec laser diffraction instrument to determine the droplet spectrum characteristics of each treatment combination. When averaged over each main effect, nozzle type had the greatest effect on droplet size. Droplet size rankings for nozzles, ranked smallest to largest using volume median diameter (Dv0.5) values, were the XR, TT, AIXR, AI, and TTI nozzle with 176% change in Dv0.5 values from the XR to the TTI nozzle. On average, increasing the nozzle orifice size from a 11003 orifice to a 11005 increased the Dv0.5 values 8%. When compared with the water treatment, cloransulam (FirstRate) did not change the Dv0.5 value. Clethodim (Select Max), glyphosate (Roundup PowerMax), lactofen (Cobra), and glufosinate (Ignite) all reduced the Dv0.5 value 5, 11, 11, and 18%, respectively, when compared with water averaged over the other variables. Increasing the pressure of AIXR, TT, TTI, and XR nozzles from 138 to 276 kPa and the AI nozzle from 276 to 414 kPa decreased the Dv0.5 value 25%. Increasing the pressure from 276 to 414 kPa and from 414 to 552 kPa for the same nozzle group and AI nozzle decreased the Dv0.5 value 14%. Carrier volume had the least effect on the Dv0.5 value. Increasing the carrier volume from 47 to 187 L ha−1 increased the Dv0.5 value 5%, indicating that droplet size of the herbicides tested were not highly dependent on delivery volume. The effect on droplet size of the variables examined in this study from greatest effect to least effect were nozzle, operating pressure, herbicide, nozzle orifice size, and carrier volume.
Response of Bell Pepper and Broccoli to Simulated Drift Rates of 2,4-D and Dicamba
Authors: Mohseni-Moghadam Mohsen , Doohan Douglas
Published: March 2015

Field experiments were conducted at Wooster, OH, in 2010 and 2011 to evaluate the effect of simulated drift rates of 2,4-D, dicamba, and 2,4-D plus glyphosate on processing broccoli and bell pepper. Treatments were made in July of each year when bell pepper and broccoli were at the 10- and eight-leaf stage, respectively, and included five 2,4-D rates (1/50, 1/100, 1/150, 1/200, and 1/400 of the recommended field rate of 840 g ae ha−1), five dicamba rates (1/50, 1/100, 1/150, 1/200, and 1/400 of the recommended field rate of 560 g ae ha−1), and three rates of 2,4-D plus glyphosate (1/100, 1/200, and 1/400 of the recommended field rates). Crop injury was recorded at 7 and 28 d after treatment (DAT). Broccoli and bell pepper responded differently to simulated drift rates each year with higher initial injury ratings observed in 2010, and more persistent symptoms in 2011. 2,4-D at the 1/50 rate reduced broccoli yield by approximately 50% in 2010. Simulated drift rates of 2,4-D did not cause broccoli yield reduction in 2011, nor did simulated drift rates of dicamba, or 2,4-D plus glyphosate reduce yield either year. Although simulated drift treatments did not reduce total yield of bell pepper, the timing of fruit maturity was affected. Yield at first harvest was reduced by high simulated drift rates of each herbicide and by the herbicide tank mix. These results indicate that broccoli and bell pepper are sensitive to very low doses of 2,4-D and dicamba that are typical of those encountered in drift events. The impact of actual drift on delayed maturity and total yield of these crops is likely to be costly for the farmer.
Nutritive Value of Field Bindweed (Convolvulus arvensis) Roots as a Potential Livestock Feed and the Effect of Aceria malherbae on Root Components
Authors: Schutte Brian J , Lauriault Leonard
Published: March 2015

Crop producers might be able to better manage field bindweed, an aggressive perennial weed, by utilizing tillage to bring roots to the surface where they can be consumed by ruminant livestock. The objectives of this study were to provide first perspectives on forage nutritive value of field bindweed roots and to determine root chemistry responses to Aceria malherbae, an eriophyid mite that has been released for field bindweed biocontrol in the western United States and Canada. To accomplish these objectives, root systems were sampled from A. malherbae-infested and noninfested plants occurring in an agricultural field in eastern New Mexico. Sampling took place during autumn and spring of each year for 3 consecutive yr. Results indicated that A. malherbae reduced taproot diameter and increased root concentrations of Ca, P, and Mg. However, A. malherbae did not affect root concentrations of acid detergent fiber, nonfiber carbohydrates, neutral detergent fiber (NDF), crude protein (CP), and total digestible nutrients (TDN). Overall means for NDF (33.8%), CP (11.6%), and TDN (72.1%) were similar to those reported for forages commonly grown in the region, suggesting that field bindweed roots might positively contribute to nutritional programs of ruminant livestock. These results justify subsequent studies on livestock responses to field bindweed roots and field bindweed responses to targeted root grazing.
Efficacy and Economics of Herbicide Programs Compared to Methyl Bromide for Weed Control in Polyethylene-Mulched Bell Pepper
Authors: Devkota Pratap , Norsworthy Jason K. , Rainey Ron
Published: March 2015

In the absence of an effective alternative to methyl bromide (MeBr), weeds cause a significant economic loss in bell pepper production. A study was conducted to evaluate the efficacy and economics of PRE followed by (fb) POST-directed (POST-DIR) herbicide programs compared with MeBr for weed control in low-density polyethylene (LDPE) mulched bell pepper production. Imazosulfuron at 0.112, 0.224, and 0.336 kg ai ha−1andS-metolachlor at 1.6 kg ai ha−1were PRE-applied fb POST-DIR applied mixture of trifloxysulfuron + halosulfuron at 0.008 and 0.027 kg ai ha−1, respectively, at 4 wk after transplanting (WATP). The standard MeBr treatment (67 and 33% mixture of MeBr + chloropicrin) was applied at 390 kg ai ha−1. In addition, a weed-free (hand weeding) and a non-treated control were used for comparison.S-metolachlor-containing herbicide program controlled Palmer amaranth ≥ 90%, large crabgrass ≥ 78%, and yellow nutsedge ≥ 90%, which were comparable to MeBr. After POST-DIR herbicide application, bell pepper was injured ≥ 17% with theS-metolachlor-containing herbicide program at 6 WATP; however, the crop later recovered. Marketable bell pepper yield in plots treated withS-metolachlor (≥ 29.9 ton ha−1) was comparable to those treated with MeBr. Economic evaluation of the imazosulfuron herbicide programs demonstrated the loss of ≥ $7,300 ha−1. Conversely, theS-metolachlor-containing herbicide program was profitable with a net return of $9,912 ha−1. In addition, theS-metolachlor herbicide program generated a net profit of $173 ha−1compared to the MeBr application. Therefore, PRE-appliedS-metolachlor fb POST-DIR applied trifloxysulfuron + halosulfuron is a potential alternative to MeBr for weed management in LDPE-mulched bell pepper production given the weed spectrum evaluated in this study.
Evaluating the Volatility of Three Formulations of 2,4-D When Applied in the Field
Authors: Sosnoskie Lynn M. , Culpepper A. Stanley , Braxton L. Bo , Richburg John S.
Published: March 2015

Cotton genetically engineered to be resistant to topical applications of 2,4-D could provide growers with an additional tool for managing difficult-to-control broadleaf species. However, the successful adoption of this technology will be dependent on the ability of growers to manage off-target herbicide movement. Field experiments were conducted in Moultrie, GA, to evaluate cotton injury resulting from the volatilization of 2,4-D when formulated as an ester, an amine, or a choline salt. Each formulation of 2,4-D (2.24 kg ha−1) was applied in mixture with glyphosate (2.24 kg ha−1) directly to the soil surface (10 to 20% crop residue) in individual square blocks (750 m2). Following herbicide applications, replicate sets of four potted cotton plants (five- to seven-leaf stage) were placed at distances ranging from 1.5 to 48 m from the edge of each treatment. Plants were allowed to remain in-field for up to 48 h before being removed. Cotton exposed to 2,4-D ester for 48 h exhibited maximum injury ratings of 63, 57, 48, 29, 13, and 2% at distances of 1.5, 3, 6, 12, 24, and 48 m, respectively. Less than 5% injury was noted for the amine and choline formulations at any distance. Plant height was also affected by formulation and distance; plants that were located closest to the ester-treated block were smaller than their more distantly-positioned counterparts. Exposure to the amine and choline formulations did not affect plant heights. Additionally, two plastic tunnels were placed inside of each treated block to concentrate volatiles and maximize the potential for crop injury. Injury ratings of 76, 13, and 5% were noted for cotton exposed to the ester, amine, and choline formulations, respectively when under tunnels for 48 h. Results indicate that the choline formulation of 2,4-D was less volatile and injurious to cotton than the ester under the field conditions in this study.
Distribution of Arable Weed Populations along Eastern Arkansas–Mississippi Delta Roadsides: Factors Affecting Weed Occurrence
Authors: Korres Nicholas E. , Norsworthy Jason K. , Bagavathiannan Muthukumar V. , Mauromoustakos Andy
Published: March 2015

The occurrence of 36 arable weed species across 13 counties in the eastern Arkansas–Mississippi Delta area on 489 randomly selected road sites was surveyed in 2012. Palmer amaranth, johnsongrass, large crabgrass, barnyardgrass, prickly sida, and broadleaf signalgrass were the top six weed species, with occurrence noted at 313, 294, 261, 238, 176, and 136 sites, respectively. Factors found to affect weed occurrence along Mississippi Delta roadsides included topographical characteristics, weed species, ditch slope, road type, and nearby land use. Among roadside topographical characteristics, road shoulder was found to strongly affect weed occurrence. In addition, paved and gravel road types with moderate roadside slope explained most of the variability of weed occurrence at each sampling site. Additionally, nearby arable land use affected weed occurrence more so than natural, residential, and pastoral land. Barnyardgrass, johnsongrass, and Palmer amaranth were 3.6 to 4.3 times more likely to occur than all other species identified. An effective weed management plan along eastern Arkansas–Mississippi Delta roadsides should focus on road shoulder, adjacent arable land use, road type, and specific weed species (e.g., Palmer amaranth, johnsongrass, and barnyardgrass). The inclusion of these parameters in future weed control programs can prove invaluable for preventing the spread of the herbicide-resistant Palmer amaranth, barnyardgrass, and johnsongrass.
Herbicide and Mulch Interactions: A Review of the Literature and Implications for the Landscape Maintenance Industry
Authors: Marble S. Christopher
Published: March 2015

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.
Inflation Dynamics During the Financial Crisis
Authors: Gilchrist Simon , Schoenle Raphael , Sim Jae W. , Zakrajsek Egon
Published: March 2015

Firms with limited internal liquidity significantly increased prices in 2008, while their liquidity unconstrained counterparts slashed prices. Differences in the firms’ price-setting behavior were concentrated in sectors likely characterized by customer markets. We develop a model, in which firms face financial frictions, while setting prices in a customer-markets setting. Financial distortions create an incentive for firms to raise prices in response to adverse demand or financial shocks. These results reflect the firms’ reaction to preserve internal liquidity and avoid accessing external finance, factors that strengthen the countercyclical behavior of markups and attenuate the response of inflation to fluctuations in output.
Lichen physiological traits and growth forms affect communities of associated invertebrates
Authors: Bokhorst Stef , Asplund Johan , Kardol Paul , Wardle David A.
Published: March 2015

While there has been much interest in the relationships between traits of primary producers and composition of associated invertebrate consumer communities, our knowledge is largely based on studies from vascular plants, while other types of functionally important producers, such as lichens, have rarely been considered. To address how physiological traits of lichens drive community composition of invertebrates, we collected thalli from 27 lichen species from southern Norway and quantified the communities of associated springtails, mites, and nematodes. For each lichen species, we measured key physiological thallus traits and determined whether invertebrate communities were correlated with these traits. We also explored whether invertebrate communities differed among lichen groups, categorized according to nitrogen‐fixing ability, growth form, and substratum. Lichen traits explained up to 39% of the variation in abundances of major invertebrate groups. For many invertebrate groups, abundance was positively correlated with lichen N and P concentrations, N:P ratio, and the percentage of water content on saturation (WC), but had few relationships with concentrations of carbon‐based secondary compounds. Diversity and taxonomic richness of invertebrate groups were sometimes also correlated with lichen N and N:P ratios. Nitrogen‐fixing lichens showed higher abundance and diversity of some invertebrate groups than did non‐N‐fixing lichens. However, this emerged in part because most N‐fixing lichens have a foliose growth form that benefits invertebrates, through improving the microclimate, independently of N concentration. Furthermore, invertebrate communities associated with terricolous lichens were determined more by their close proximity to the soil invertebrate pool than by lichen traits. Overall, our results reveal that differences between lichen species have a large impact on the invertebrate communities that live among the thalli. Different invertebrate groups show contrasting responses to traits that are indicative of thallus quality (nutrient concentrations), and thallus growth form is often an important determinant of the invertebrate community. Given the large diversity of lichen traits and growth forms that occur in many ecosystems, lichen–invertebrate communities may be an important contributor to overall community diversity in boreal forests.
Phytoplankton traits predict ecosystem function in a global set of lakes
Authors: Zwart Jacob A. , Solomon Christopher T. , Jones Stuart E.
Published: March 2015

Predicting ecosystem function from environmental conditions is a central goal of ecosystem ecology. However, many traditional ecosystem models are tailored for specific regions or ecosystem types, requiring several regional models to predict the same function. Alternatively, trait‐based approaches have been effectively used to predict community structure in both terrestrial and aquatic environments and ecosystem function in a limited number of terrestrial examples. Here, we test the efficacy of a trait‐based model in predicting gross primary production (GPP) in lake ecosystems. We incorporated data from >1000 United States lakes along with laboratory‐generated phytoplankton trait data to build a trait‐based model of GPP and then validated the model with GPP observations from a separate set of globally distributed lakes. The trait‐based model performed as well as or outperformed two ecosystem models both spatially and temporally, demonstrating the efficacy of trait‐based models for predicting ecosystem function over a range of environmental conditions.
Sand Prediction: A Practical Finite-Element 3D Approach for Real Field Applications
Authors: Volonté G.. , Scarfato F.. , Brignoli M..
Published: March 2015

Sand production is a critical issue in the oil and gas industry. During the production of a well, sand production may have negative consequences, such as risk of well failure, erosion of pipelines and surface facilities, and the need for sand separation and disposal. Knowing the conditions for the onset of sand production allows optimizing sand free production and, eventually, avoiding or delaying the use of sand-control methods.

The aim of this work is to establish a reliable workflow for the estimation of the conditions for sand production in real field cases by means of finite-element modeling. The fundamental requirement is to set up a 3D coupled model that can be easily adjusted to the most complex conditions (e.g., stress anisotropy, deviated wells, and complex perforation patterns).

The most suitable geometries and associated meshing strategies to describe the wellbore, the perforation tunnels, and the surrounding formation are analyzed. Further improvements with respect to previous approaches include the fact that the drilling and completion phases were also simulated to compute the correct stress distribution before the production, and that fluid flow and rock deformation are simulated in a fully coupled way to investigate accurately the effect of drawdown.

Shear failure of reservoir rock, considered as an elastoplastic medium, is the main sand-production mechanisms analyzed, and the damage of the rock around the perforations is evaluated by analyzing the distribution of the equivalent plastic strain.

Two real field cases are simulated, and the results of the finite-element models are consistent with the ones obtained by means of an analytical models and with field observations. Moreover, this numerical approach allows quantifying the spatial distribution and the severity of the damage of the rock around the perforations, facts that are either oversimplified or not considered at all in analytical models.

For future applications, this model can be straightforwardly extended to more complex conditions and can also be improved to provide volumetric sand prediction.
Effect of Oil Saturation on the Flow of Emulsified Acids in Carbonate Rocks
Authors: Sayed Mohammed A. , Assem Ahmed I. , Nasr-El-Din Hisham A.
Published: March 2015

Matrix acid treatments in carbonate reservoirs target stimulation of the near-well region. Emulsified acid can be used in matrix acidizing and acid-fracturing treatments. The delayed nature of emulsified acid is useful in creating deep wormholes and etched fracture surfaces. Almost all previous coreflood work was performed on cores fully saturated with water. Therefore, the main objective of the present work is to study the effect of oil saturation in the formation on the flow of emulsified acids in carbonate cores and assess the performance of emulsified acid in stimulating carbonate formations.

A coreflood study was conducted using Indiana limestone cores that were 1.5 in. in diameter and 6 in. in length. The effect of the presence of crude oil on the volume of acid to breakthrough was studied. Also, the size, number, and distribution of the wormholes were determined with computed-tomography (CT) images. The effect of the acid injection rate on the performance of emulsified acid was investigated. Cores that were fully saturated with water, fully saturated with crude oil, and saturated with crude oil at irreducible water saturation were used. There was no optimum injection rate for emulsified acids when they were injected into Indiana limestone cores with permeabilities of 47 to 238 md. In such a range of permeability, emulsified acid enhanced the rock permeability when the acid was injected at both high (10.0 cm3/min) and low (0.5 cm3/min) rates. For cores fully saturated with crude oil, the volume of emulsified acid to achieve breakthrough was 2.2 times more than that required to achieve breakthrough in cores fully saturated with water. The increase in emulsified-acid volume refers to the increase in the volume of the continuous phase resulting from the mixture of the crude oil and diesel and the subsequent change in the acid/diesel volume fraction. As a result, more acid was consumed to create wormholes and achieve the breakthrough. The emulsified-acid system was effective in stimulating limestone cores, whether these cores were saturated with water, oil, or oil at irreducible water saturation.
Simulation of Fracturing-Induced Formation Damage and Gas Production From Fractured Wells in Tight Gas Reservoirs
Authors: Ding D.Y.. Y. , Langouët H.. , Jeannin L..
Published: March 2015

Fracturing fluid may jeopardize the production of hydraulically fractured tight gas formations. Because capillary forces act stronger in low-permeability formations, the invaded fracturing fluid is harder to remove. The increase of water saturation around the fractured well affects the mobility of the gas phase, particularly in tight formations where the gas relative permeability declines strongly when water saturation increases. This damage might greatly reduce the gas production in a very long cleanup period. This paper presents numerical simulation techniques to account for formation damage with both a near-well model and a full-field model for fractured wells in tight formations. For the full-field model, the skin determined from an inversion is suitable for long-term production simulations, and a sector model can be used to update the well skin through a coupled modeling so that the full-field model can be used correctly over the whole life of the project.
CFD Modeling and Experimental Observations of Changing Surface Profiles Caused by Solid-Particle Erosion
Authors: Wong Chong Y. , Solnordal Christopher B. , Wu Jie
Published: March 2015

Traditional erosion modeling on oil and gas equipment frequently assumes a fixed erosion rate and unchanging surface profile throughout the erosion-exposure period. This approach does not account for the constantly changing surface and changes in the fluid flow, and therefore may lead to unquantified uncertainties in the prediction of equipment life. The literature presents limited experimental data of generic configurations in this topic. This paper addresses this gap by simultaneously investigating three generic configurations often encountered in oil and gas facilities. These configurations are a cylindrical rod, a hole in a flat plate, and a pipe cavity. Various eroded profiles of the physical configurations will be compared with traditional computational-fluid-dynamics (CFD) modeling with an unchanging model surface.

To validate this traditional assumption, the authors have used a modeling approach with multilayer paint modeling and geometry surface profiling of the aforementioned configurations exposed to a flow field with ambient air suspended with dilute solid particles.
Minimizing Environmental and Economic Risks With a Proppant-Sized Solid-Scale-Inhibitor Additive in the Bakken Formation
Authors: Szymczak Steve , Shen Dong , Higgins Rocky , Gupta D.V. Satya
Published: March 2015

Within the past decade, hydraulic fracturing has proved to enhance the efficiency and economics of recovering oil and natural gas from shale formations. In a previous paper (SPE-134414-MS, Gupta et al. 2010), a summary of treatment results from placing a solid scale inhibitor into formations by means of the fracturing process for more than 5 years and in more than 1,500 wells was discussed fully; however, the practice of hydraulic fracturing has come under scrutiny because of concerns about environmental impact, health, and safety. Therefore, a novel, biodegradable scale inhibitor with an outstanding ecotoxicity profile for fresh water incorporated into a solid matrix was recently developed and deployed in North Dakota. For one operator with 150 Bakken producing wells in this area, severe carbonate-mineral scaling in the pump and production tubing has been observed in 22 of these producing wells, which led to well failure (Cenegy et al. 2011), whereas the results from more than 290 Bakken wells now fractured with the new solid-inhibitor additives indicate no reported scale failures to date.

This paper provides a detailed description of the first deployment of this environmentally preferred proppant-sized solid-scale-inhibitor additive under severe scaling conditions in the field. In addition, an analytical method developed to track the residual of this additive in the produced fluid containing polysaccharide contaminants is also discussed.
Experimental Investigation of Pressure-Drop/Flow-Rate Relationship for Small-Aperture Holes for High-Viscosity Fluids
Authors: Jain Rachna , Long Ted A. , Dickson Jasper , Brown Scott V. , Shtepani Edmond
Published: March 2015

This paper studies the effect of viscosity and fines-particle loading on the pressure drop across a 4-mm orifice in a specific geometry built to mimic a representative well completion. It also provides experimental data in the range of operating conditions (high aspect ratio, low Reynolds number) that were not covered by any previous studies. The past experiments concentrated on studying the orifices with high aspect ratio (>1) and high Reynolds number (>1,000) or with a combination of low aspect ratio and low Reynolds number. In previous research conducted within the petroleum industry, most of these orifices were validated experimentally for viscosities up to 200 cp only for such completions. The current study focused on a wider viscosity variation (1 to 3,000 cp) with lower flow rates (0.5 to 30 m3/d). Even though fines are an integral part of the flow stream passing through the orifice for a sand reservoir, none of these studies further considered the effect of small particles on the orifice performance. The pressure drop was measured across the orifice and through the entire pipe assembly. The measured data were nondimensionalized by use of the Euler number and plotted against the Reynolds number for all rates and viscosities. The data were also compared and validated against commercially available computational-fluid-dynamics (CFD) software. The effect of sand-particle loading was also studied, and its effect on apparent viscosity increase was measured in the laboratory. The pressure-drop/flow-rate relationship and flow coefficient disclosed in this paper can be used to design effective completions for intermediate- to high-viscosity-oil applications and will be able to predict the completion pressure drop more accurately.
Full-Scale Testing Shows Advantages of a Quantitative Approach to Interpreting Inflow Tests
Authors: Rahmani R.. , Bourgoyne D.. , Smith J.R.. R.
Published: March 2015

An inflow (commonly known as negative pressure) test is an important step in proving well integrity for some well operations. Although the concept is straightforward, there are no standard procedures for conducting and interpreting inflow tests. Recent industry experience has shown the potential for these tests to be misinterpreted, with disastrous results. This paper describes proper quantitative interpretation of both successful and unsuccessful tests demonstrated on two full-scale test wells.

Tests with and without leaks are simulated in two vertical wells with 2,971- and 5,884-ft depths. Test results are interpreted quantitatively to distinguish successes from failures. In addition, the impacts of leak rate and the differential pressure between the leak source and well are investigated. The impacts of gas as a leak fluid, different well volumes, different surface-piping arrangements, and measuring with different-sensitivity tanks are also shown.

The success of a test should be verified with both flow and pressure checks. For the flow check, the trend between bleed-off pressure and volume of bleedoff can be predicted on the basis of fluid compressibility, tubing expansion, and drainage from surface piping. Deviations from that trend will identify the onset of a leak. Early detection and control of a high-rate leak can reduce the formation-fluid volume entering the well and the consequent risks. Detecting a low-rate leak is difficult if the test duration is too short. Therefore, a 30-minute test duration was evaluated for detection of low-rate leaks.

The fundamental differences between a leak and no leak are demonstrated conclusively with quantitative results. Approaches for overcoming complications that interfere with conclusive test results are explained and demonstrated. The demonstration test results and the proposed interpretation methods are applicable to vertical wells. Drilling-fluid properties, multiple fluids, and thermal expansion can also influence results, but were not investigated in this study. Nevertheless, these results should provide a basis for improving field procedures and minimizing the risk of misinterpreting a leak as a successful test.
Structure, Stoichiometry, and Modeling of Calcium Phosphonate Scale-Inhibitor Complexes for Application in Precipitation-Squeeze Processes
Authors: Shaw S.S.. S. , Sorbie K.S.. S.
Published: March 2015

Phosphonate scale inhibitors (SIs) applied in downhole-squeeze applications may be retained in the near-well formation through adsorption and/or precipitation mechanisms. In this paper, we focus on the properties of precipitated calcium phosphonate complexes formed by nine common phosphonate species. The stoichiometry [calcium ion to phosphorous (Ca2+/P) ratios] in various precipitates is established experimentally, and the effect of solution pH on the molar ratio of Ca2+/P in the precipitate is investigated. All static precipitation tests were carried out in distilled water (DW), with only Ca2+ [as calcium chloride (CaCl2)] and SI present in the system at test temperatures from 20 to 95°C. The molar ratio of Ca2+/P in the solid precipitate was determined by assaying for Ca2+ and P in the supernatant liquid under each test condition by inductively coupled plasma (ICP) spectroscopy (Ca0 and P0 are known, but are also measured experimentally). We show experimentally that the molar ratio of precipitated Ca2+/P (or Ca2+/SI; or n in the SI–Can complex) depends on the SI itself and is a function of pH for all phosphonates tested. It is found that, as pH increases, the molar ratio of Ca2+/P (n in the SI–Can) in the precipitate increases up to a theoretical maximum, depending on the chemical structure of the phosphonate. Our findings corroborate proposed SI-metal complex-ion structures, which were presented previously in Shaw et al. (2012c), as discussed in detail in this paper. In addition, the precipitation behavior of the various compounds is modeled theoretically by developing and solving a set of simplified equilibrium equations. We find that the precipitation behavior can be modeled, but only if a fraction (β) of “non-SI” of the initial phosphonate SI is taken into account. The quantity β can be as high as 0.2 (i.e., approximately 20% non-SI), although there is a degree of variability in this factor from product to product. However, good quantitative agreement is shown comparing the predictions of the equilibrium-solubility model with the experiment. Such models can be used directly in the modeling of field phosphonate precipitation-squeeze treatments.