bluuebunny/crossref_metadata_2025 huggingface dataset:
Graded levels of Pax2a and Pax8 regulate cell differentiation during sensory placode formation
Authors: McCarroll Matthew N. , Lewis Zachary R. , Culbertson Maya Deza , Martin Benjamin L. , Kimelman David , Nechiporuk Alex V.
Published: June 2012

Pax gene haploinsufficiency causes a variety of congenital defects. Renal-coloboma syndrome, resulting from mutations in Pax2, is characterized by kidney hypoplasia, optic nerve malformation, and hearing loss. Although this underscores the importance of Pax gene dosage in normal development, how differential levels of these transcriptional regulators affect cell differentiation and tissue morphogenesis is still poorly understood. We show that differential levels of zebrafish Pax2a and Pax8 modulate commitment and behavior in cells that eventually contribute to the otic vesicle and epibranchial placodes. Initially, a subset of epibranchial placode precursors lie lateral to otic precursors within a single Pax2a/8-positive domain; these cells subsequently move to segregate into distinct placodes. Using lineage-tracing and ablation analyses, we show that cells in the Pax2a/8+ domain become biased towards certain fates at the beginning of somitogenesis. Experiments involving either Pax2a overexpression or partial, combinatorial Pax2a and Pax8 loss of function reveal that high levels of Pax favor otic differentiation whereas low levels increase cell numbers in epibranchial ganglia. In addition, the Fgf and Wnt signaling pathways control Pax2a expression: Fgf is necessary to induce Pax2a, whereas Wnt instructs the high levels of Pax2a that favor otic differentiation. Our studies reveal the importance of Pax levels during sensory placode formation and provide a mechanism by which these levels are controlled.
A genome-wide transgenic resource for conditional expression ofDrosophilamicroRNAs
Authors: Bejarano Fernando , Bortolamiol-Becet Diane , Dai Qi , Sun Kailiang , Saj Abil , Chou Yu-Ting , Raleigh David R. , Kim Kevin , Ni Jian-Quan , Duan Hong , Yang Jr-Shiuan , Fulga Tudor A. , Van Vactor David , Perrimon Norbert , Lai Eric C.
Published: June 2012

microRNAs (miRNAs) are endogenous short RNAs that mediate vast networks of post-transcriptional gene regulation. Although computational searches and experimental profiling provide evidence for hundreds of functional targets for individual miRNAs, such data rarely provide clear insight into the phenotypic consequences of manipulating miRNAs in vivo. We describe a genome-wide collection of 165 Drosophila miRNA transgenes and find that a majority induced specific developmental defects, including phenocopies of mutants in myriad cell-signaling and patterning genes. Such connections allowed us to validate several likely targets for miRNA-induced phenotypes. Importantly, few of these phenotypes could be predicted from computationally predicted target lists, thus highlighting the value of whole-animal readouts of miRNA activities. Finally, we provide an example of the relevance of these data to miRNA loss-of-function conditions. Whereas misexpression of several K box miRNAs inhibited Notch pathway activity, reciprocal genetic interaction tests with miRNA sponges demonstrated endogenous roles of the K box miRNA family in restricting Notch signaling. In summary, we provide extensive evidence that misexpression of individual miRNAs often induces specific mutant phenotypes that can guide their functional study. By extension, these data suggest that the deregulation of individual miRNAs in other animals may frequently yield relatively specific phenotypes during disease conditions.
Sequential Release of Single-stranded DNAs from Gold Nanorods Triggered by Near-infrared Light Irradiation
Authors: Fukushima Hiromitsu , Yamashita Shuji , Mori Takeshi , Katayama Yoshiki , Niidome Takuro
Published: June 2012

Gold nanorods were modified with two types of double-stranded DNAs (dsDNA) with different melting temperatures. Irradiated by near-infrared laser light, the modified gold nanorods were heated, and single-stranded DNAs were released faster from the dsDNA with the lower melting temperature. Such combinations of different kinds of dsDNA allow us to construct a two-step release system of different types of oligonucleotides.
SO42−/CexZr1−xO2-catalyzed Synthesis of N-tert-Butylamides from Various Nitriles under Solvent-free Conditions
Authors: Kahandal Sandeep S , Kale Sandip R , Disale Shamrao T , Jayaram Radha V
Published: June 2012

The synthesis of N-tert-butylamides using SO42−/CexZr1−xO2 catalysts under solvent-free conditions is reported. The methodology has several advantages such as reusability of the catalyst, solvent-free conditions, easy workup, and comparable yield of N-tert-butylamides. A variety of aliphatic, aromatic, and acid-sensitive substrates give high to moderate yields of the corresponding N-tert-butylamides. Surface acidities of the catalysts were correlated with the results obtained. To the best of our knowledge, this is the first report of a modified Ritter reaction on SO42−/CexZr1−xO2 using tert-butyl acetate as carbocationic source.
Prevalence of glucose-6-phosphate dehydrogenase deficiency among neonates at a tertiary care centre in Lebanon
Authors: Inati Adlette , Abbas Hussein A , Boumitri Christine , Tecle Najib
Published: June 2012

In this study we aimed to determine the prevalence of glucose-6-phosphate dehydrogenase (G6PD) deficiency in a Lebanese population and the clinical outcomes and associated adverse events encountered amongst affected patients. Newborn screening in a tertiary care centre in North Lebanon showed a prevalence of 2.1% (62 out of 3009), significantly higher in males than females, and in Muslims than Christians. Among 45 infants followed for a median of 2.2 years from birth, 12 (27%) were admitted to hospital for severe haemolytic crises, despite a programme of early family education and close follow-up. A nationwide newborn screening program to identify afflicted individuals, and to augment vigilance about this disease, should be considered in countries where the disorder is prevalent.
The Sediment Erosion Rate Flume (SERF): A New Testing Device for Measuring Soil Erosion Rate and Shear Stress
Authors: Crowley Raphael W. , Bloomquist David B. , Shah Falak D. , Holst Courtney M.
Published: June 2012

A new apparatus that measures soil erosion in a flume is described. It is designed to measure a bed material’s erosion rate and approximate its corresponding applied shear stress (erosion function). The apparatus, or Sediment Erosion Rate Flume (SERF), is unlike similar devices, in that during an erosion test, sample advancement is computer-controlled through a feedback loop via a series of lasers, ultrasonic depth sensors, and a Servo-stepper motor. Because of this computerized control mechanism, the SERF can be used to measure near-instantaneous erosion rate as opposed to average erosion rate over an elapsed time domain. Also, included with the SERF is a device that can measure shear stress directly for a sample with a certain uniform roughness. Using the SERF, erosion versus time curves were used to estimate erosion rate for both synthetic and natural samples. For synthetic samples, a roughness approximation was conducted to estimate shear stress. Tests with the shear stress sensor appear to indicate that smooth-wall approximations used in previous flume-style erosion rate testing apparatuses under-predict shear stress. However, further analysis of erosion results indicates that the smooth-wall approximation is conservative; and until a direct method for measuring shear stress is discovered, it may be appropriate for devices like this. Using this rationale, erosion functions were estimated for natural samples.
Identification of Low-Organic-Content Soils: An Engineering Approach
Authors: Huang Pao-Tsung , Bobet Antonio , Santagata Marika
Published: June 2012

From a geotechnical engineering perspective, the presence of organic matter in soils can often be a concern, because of its negative impact on many mechanical properties and its potential interference with soil stabilization reactions. For this reason, many regulating agencies have strict limits on the maximum allowable organic content in subgrade soils and backfills, requiring that it fall below a threshold value in the 2 %−7 % range. Methods currently used in practice for the identification of organic soils and for the quantification of organic matter have shortcomings when applied to soils with organic matter content less than ∼10 %−15 %. For such soils, the loss on ignition often overestimates the true organic content, and the criteria employed by the ASTM and the American Association of State Highway and Transportation Officials classification systems are generally insensitive to the presence of these amounts of organic matter. This paper presents the results of a study conducted to identify a practical approach for the identification of soils with organic content in the 3 %−15 % range. The study explored the relationship between true organic content, as determined through the dry combustion test, and the results of three tests: loss on ignition, Atterberg limits (with and without oven drying), and the colorimetric test. Tests were conducted on a number of natural soil samples, select clay minerals, and three types of laboratory-prepared soils. It was found that the combined use of these tests is effective in screening soils for the presence of percentages of organic matter in the 3 %−15 % range. Results of thermal gravimetric analyses, differential scanning calorimetry, and x-ray diffraction analyses performed on select tests provide an improved scientific understanding of the results.
The Role of Ballast-Fouling Characteristics on the Drainage Capacity of Rail Substructure
Authors: Tennakoon Nayoma , Indraratna Buddhima , Rujikiatkamjorn Cholachat , Nimbalkar Sanjay , Neville Tim
Published: June 2012

The ballast layer is designed to be free draining, but when the voids of the granular medium are wholly or partially filled because of the intrusion of fine particles, the ballast is considered to be “fouled.” To ensure acceptable track performance, it is necessary to maintain good drainage within the ballast layer. This paper critically examines the current methods commonly used for evaluating the degree of ballast fouling and, because of their limitations, a new parameter, “void contaminant index” is introduced. A series of large-scale constant head hydraulic conductivity tests were conducted with different levels of fouling to establish the relationship between the void contamination index and the associated hydraulic conductivity. Subsequently, a numerical analysis was executed to simulate more realistic two-dimensional flow under actual track geometry capturing the drainage capacity of ballast in relation to the void contamination index. In the context of observed test data, the drainage condition of the track could be classified into different categories together with a classification chart capturing the degree of fouling. The contents of this paper have already been considered in track maintenance schemes in the states of Queensland and New South Wales.
Whole-Genome Regression and Prediction Methods Applied to Plant and Animal Breeding
Authors: de los Campos Gustavo , Hickey John M , Pong-Wong Ricardo , Daetwyler Hans D , Calus Mario P L
Published: June 2012

Genomic-enabled prediction is becoming increasingly important in animal and plant breeding and is also receiving attention in human genetics. Deriving accurate predictions of complex traits requires implementing whole-genome regression (WGR) models where phenotypes are regressed on thousands of markers concurrently. Methods exist that allow implementing these large-p with small-n regressions, and genome-enabled selection (GS) is being implemented in several plant and animal breeding programs. The list of available methods is long, and the relationships between them have not been fully addressed. In this article we provide an overview of available methods for implementing parametric WGR models, discuss selected topics that emerge in applications, and present a general discussion of lessons learned from simulation and empirical data analysis in the last decade.
Influence of unsteady flow hydrograph shape on local scouring around bridge pier
Authors: Borghei Seyed Mahmood , Kabiri-Samani Abdorreza , Banihashem Seyed Arash
Published: June 2012

Accurate estimation of scour depth is needed for economic and safe determination of bridge pier foundation depth. Most design criteria are based on maximum scour depth due to the steady design discharge without flow time limit. In this paper, the results are presented of an experimental investigation on local scouring around a single bridge pier under steady and unsteady flow regimes. For unsteady flow, triangular shape hydrographs with repeatable peaks have been chosen. Results show that both sharp and flat increases to the peak of hydrographs have a negligible effect on scour depth for the same base time. An equation is obtained to compute the scour depth due to a specific triangular hydrograph with specific base time, peak flow characteristics and pier diameter. Also, an equation is introduced to represent temporal variation of scour depth with respect to the steady flow condition.
Variation in photosynthetic response to temperature in a guild of winter annual plants
Authors: Gremer Jennifer R. , Kimball Sarah , Angert Amy L. , Venable D. Lawrence , Huxman Travis E.
Published: June 2012

How species respond to environmental variation can have important consequences for population and community dynamics. Temperature, in particular, is one source of variation expected to strongly influence plant performance. Here, we compared photosynthetic responses to temperature across a guild of winter annual plants. Previous work in this system identified a trade‐off between relative growth rate (RGR) and water‐use efficiency (WUE) that predicts species differences in population dynamics over time, which then contribute to long‐term species coexistence. Interestingly, species with high WUE invest in photosynthetic processes that appear to maximize carbon assimilation, while high‐RGR species appear to maximize carbon gain by increasing leaf area for photosynthesis. In high‐WUE species, higher rates of carbon acquisition were associated with increased investment into light‐driven electron transport (Jmax). We tested whether such allocation allows these plants to have greater photosynthetic performance at lower temperatures by comparing the temperature sensitivity of photosynthesis across species in the community. Six species were grown in buried pots in the field, allowing them to experience natural changes in seasonal temperature. Plants were taken from the field and placed in growth chambers where photosynthetic performance was measured following short‐term exposure to a wide range of temperatures. These measurements were repeated throughout the season. Our results suggest that high‐WUE species are more efficient at processing incoming light, as measured by chlorophyll fluorescence, and exhibit higher net photosynthetic rates (Anet) than high‐RGR species, and these advantages are greatest at low temperatures. Sampling date differentially affected fluorescence across species, while species had similar seasonal changes in Anet. Our results suggest that species‐specific responses to temperature contribute to the WUE–RGR trade‐off that has been shown to promote coexistence in this community. These differential responses to environmental conditions can have important effects on fitness, population dynamics, and community structure.
Fossil Energy Use in Conventional and Low‐External‐Input Cropping Systems
Authors: Cruse Michael J. , Liebman Matt , Raman D. Raj , Wiedenhoeft Mary H.
Published: June 2012

Conventional agriculture production systems in developed countries rely heavily on fossil energy, but emerging uncertainties in fossil fuel supply indicate a need to better understand energy efficiency in conventional and alternative systems. We used 6 yr of data from a cropping systems experiment conducted in Iowa to compare energy use of a conventionally managed corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] system (a 2‐yr rotation) with two low‐external input (LEI) cropping systems that used more diverse rotations and manure, but substantially lower quantities of synthetic N fertilizer and herbicides. Depending on how fossil energy costs were assigned to manure, the two LEI systems (a 3‐yr rotation of corn–soybean–small grain/red clover (Trifolium pratense L.), and a 4‐yr rotation of corn–soybean–small grain/alfalfa–alfalfa, Medicago sativa L.) used between 14 and 53% less fossil energy than did the conventional system. In general, the primary category for fossil energy use was fertilizer. The conventional 2‐yr system used substantially more fossil energy embodied in synthetic fertilizers and pesticides than did the LEI systems. Economic return, harvested crop weight, and potential energy production of the conventional 2‐yr and LEI 4‐yr systems were similar. Efficiency ratios, including crop energy output and economic return per unit of fossil energy invested, were significantly higher in the LEI 4‐yr rotation than in the conventional system. In coming years, if fossil energy prices rise significantly without concomitant increases in crop value, diversified LEI systems may become preferable to conventional cropping systems and used more widely.
Comparative Breakeven Analysis of Annual Grain and Perennial Switchgrass Cropping Systems on Claypan Soil Landscapes
Authors: Landers Greg W. , Thompson Allen L. , Kitchen Newell R. , Massey Ray E.
Published: June 2012

The Central Claypan region is an important agricultural production contributor in the U.S. Midwest. Because of the tendency for grain yield fluctuations caused by water stress, however, claypan soils may have potential for conversion from grain to grass production in support of biomass energy markets and conservation programs. This study examined the economic potential of transitioning from grain to perennial switchgrass (Panicum virgatum L.) production on claypan soils using comparative breakeven analysis. Partial budgets for a corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation and a perennial switchgrass cropping system were developed. Yield data from research plots with varying topsoil depths defined by the underlying claypan layer were used to establish yield expectations as affected by topsoil depth. Switchgrass yield projections for the claypan region were simulated with the Agricultural Land Management Alternatives with Numerical Assessment Criteria (ALMANAC) model. Comparative breakeven prices for two switchgrass cultivars ranged from US$65 on marginal, eroded soils to US$124 Mg−1 on soils with >27 cm of topsoil. Breakeven yields with a biomass price of US$40 Mg−1 would require yield increases of up to 450% for lower yielding cultivars. The switchgrass cultivar Kanlow holds the most promise for biomass production on claypan soils; with an average projected yield of 12.56 Mg ha−1, breakeven prices fall to around US$60–80 Mg−1 for marginal soils with <15 cm of topsoil. Based on these projections, perennial switchgrass shows potential to compete with conventional grain crops at reasonable yield levels on eroded soils in the Central Claypan region.
Improved Management Alleviating Impact of Water Stress on Yield Decline of Tropical Aerobic Rice
Authors: Ghosh A. , Dey R. , Singh O. N.
Published: June 2012

Yield decline is the major concern in tropical aerobic rice (Oryza sativa L.). Both biotic and abiotic factors were responsible for this phenomenon. No analytical information on actual causes was reported taking into account of responses of root to water stress conditions. In a field experiment at the Central Rice Research Institute, India during 2009 and 2010, five rice genotypes were grown under two soil water conditions, aerobic and semi‐aerobic condition, for better understanding of yield penalty vis‐à‐vis yield stability. Results showed aerobic condition significantly inhibited structural development of root and caused significant variation in biochemical root traits accounting for higher concentration of hydrogen peroxide (24.6%) and proline (20%), and lower concentration of total soluble protein (20%) that resulted in 17% yield decline than semi‐aerobic condition. Applying supplementary irrigation at semi‐aerobic condition achieved 21% more grain yield compared with aerobic condition due to 21%, 8.3, and 10.4% more root biomass, root volume, and root/shoot ratio, respectively. Interaction of genotypes with soil water conditions revealed that at aerobic condition, better performance could be expected in ‘Apo’(4.0 t ha−1) and ‘IR 74371‐3‐1‐1’ (3.80 t ha−1) with less yield decline (7.0–9.5%); supplementary irrigation enhanced their grain yield (4.3–4.4 t ha−1) at semi‐aerobic condition. Therefore, detrimental impact of physical and biochemical root traits’ changes on yield decline in aerobic rice could be alleviated with supplementary irrigation at critical growth stages under semi‐aerobic condition without compromising with water productivity.
The Effects of Seeding Rate on Older Stands of Glyphosate‐Tolerant Alfalfa
Authors: Hall M. H. , Dillon J. M. , Stambaugh H. J. , Hebrock N. S. , Caddel J. L. , Owens V. N. , Sulc R. M. , Undersander D. J. , Whitesides R. E.
Published: June 2012

Increased seed cost of glyphosate tolerant (GT) compared to non‐GT alfalfa (Medicago sativa L.) raises questions about reducing seeding rates. The objective of this study was to determine if alfalfa stand density, yield, and forage quality are compromised in the later years of the stand when reduced seeding rates, in combination with glyphosate application, were used during establishment. At seven locations in the United States, GT alfalfa was seeded into conventionally tilled seedbeds at 6.7, 11.2, 15.7, and 20.2 kg ha−1 pure live seed (PLS) in the spring of 2006. Stand density, yield, and forage quality were determined for each seeding rate under three herbicide treatments: (i) glyphosate [N‐(phosphonomethyl)glycine], (ii) non‐glyphosate herbicide, and (iii) no herbicide. For the third through fifth years of the alfalfa stand, there was no herbicide treatment × seeding rate interaction. Higher seeding rates resulted in higher plant densities. The 11.2 and 15.7 kg ha−1 seeding rates had greater alfalfa and total forage (alfalfa + weeds) yields than the 6.7 kg ha−1 seeding rate. Herbicide treatments had no effect on alfalfa plant density but produced cumulative (over the duration of the study) alfalfa yield in the following order: glyphosate > non‐glyphosate > no herbicide. Cumulative total forage yield was less when no herbicide was used compared to using a herbicide. While forage fiber content was generally unaffected by seeding rate or herbicide treatments, using glyphosate to control weeds during alfalfa establishment increased forage crude protein content of older alfalfa stands compared to no weed control.
Alfalfa Yield Components and Soil Potassium Depletion as Affected by Potassium Fertilization
Authors: Lloveras Jaume , Chocarro Cristina , Torres Lluis , Viladrich Denis , Costafreda Ramon , Santiveri Francisca
Published: June 2012

Potassium fertilization recommendations for alfalfa (Medicago sativa L.) vary depending on the area of production, soil levels, and crop management. The objectives of this study were to determine the impact of K fertilization on irrigated alfalfa yield, yield components, and soil exchangeable K (Ke) values in a Mediterranean climate. A field experiment was conducted during a period of 4 yr (2002–2006) in Spain, on a soil with moderate levels of Ke (161 mg K kg−1). The treatments applied were five annual rates of K (0, 100, 200, 300, and 400 kg K ha−1). Total 4‐yr dry matter (DM) yields averaged 74.9 Mg ha−1 without differences between K fertilizer rates, although the unfertilized control produced the lowest DM yields. The 4‐yr crop uptake of K reached 1738 kg ha−1 with the application of 400 kg K ha−1 yr−1, and 756 kg K ha−1 for the 0 K fertilization. The removal was greater than the K applied. The results suggest that large amounts of K should not be applied to alfalfa because the crop uses excess K without increasing yield. Soil Ke concentrations decreased every year for all K rates except for the highest treatment of 400 kg K ha−1 yr−1. Lack of K fertilization did not affect stand density but the shoot weight was the yield component most closely related to K fertilization.
Reduced‐Tillage Organic Corn Production in a Hairy Vetch Cover Crop
Authors: Teasdale John R. , Mirsky Steven B. , Spargo John T. , Cavigelli Michel A. , Maul Jude E.
Published: June 2012

There is interest in developing no‐tillage systems for organic farming; however, potential limitations include the inability to control weeds and to provide sufficient crop available N. A 3‐yr field experiment was conducted on organically certified land to explore roller‐crimper technology for terminating a hairy vetch (Vicia villosa Roth) cover crop in a reduced‐tillage compared to a disk‐tillage organic corn (Zea mays L.) production system in Maryland. Within this tillage comparison, factors including the corn planting date and post‐plant cultivation were examined for optimizing reduced‐tillage organic corn production. Corn yield in roll‐killed hairy vetch treatments where corn was planted by mid‐June and that received high‐residue cultivation was similar or higher than the best treatments with disk‐killed hairy vetch. Delayed corn planting dates had little impact on corn yield in either disk‐ or roll‐killed treatments, a result consistent with the similarity in weed biomass after cultivation, fertility, moisture, and radiation across planting dates. In 2 yr with supplemented weed populations, weed biomass was the major driver determining corn yield, which was reduced by 53 to 68% relative to weed‐free control plots in the absence of post‐plant cultivation, and by 21 to 28% with post‐plant cultivation. In a year with low, natural weed populations, weeds had no significant influence on yield. These results demonstrate that organic corn production in a reduced‐tillage roll‐killed cover crop system can provide similar yields to those in a traditional tillage‐based system, but also highlight the importance of maintaining low weed populations to optimize corn yield.
Winter Cover Crop Seeding Rate and Variety Affects during Eight Years of Organic Vegetables: I. Cover Crop Biomass Production
Authors: Brennan Eric B. , Boyd Nathan S.
Published: June 2012

Long‐term research on cover crops (CC) is needed to design optimal rotations. Winter CC shoot dry matter (DM) of rye (Secale cerealeL.), legume–rye, and mustard was determined in December to February or March during the first 8 yr of the Salinas Organic Cropping Systems trial focused on high‐value crops in Salinas, CA. By seed weight, legume–rye included 10% rye, 35% faba (Vicia fabaL.), 25% pea (Pisum sativumL.), and 15% each of common vetch (V. sativaL.) and purple vetch (V. benghalensisL.); mustard included 61% Sinapis albaL. and 39% Brassica junceaCzern. Cover crops were fall‐planted at 1x and 3x seeding rates (SR); 1x SR were 90 (rye), 11 (mustard), and 140 (legume–rye) kg ha−1. Vegetables followed CC annually. Cover crop densities ranged from 131 to 854 plants m−2and varied by CC, SR, and year. Year, CC, and SR affected DM production, however, the effects varied across the season and interactions occurred. Averaged across years, final DM was greater in rye and legume–rye (7 Mg ha−1) than mustard (5.6 Mg ha−1), and increased with SR through January. Dry matter production through the season was correlated significantly with growing degree days (GDD). Legumes contributed 27% of final legume–rye DM. Season‐end legume DM was negatively correlated with GDD at 30 d, and legume DM in the 3x SR increased during years with frequent late‐season rainfall. Seed costs per Mg of final CC DM at 1x SR were approximately three times higher for legume–rye than rye and mustard.
Winter Cover Crop Seeding Rate and Variety Affects during Eight Years of Organic Vegetables: II. Cover Crop Nitrogen Accumulation
Authors: Brennan Eric B. , Boyd Nathan S.
Published: June 2012

Winter cover crops (CC) can improve nutrient use efficiency by scavenging residual soil N. Shoot nitrogen accumulation (NA) of rye (Secale cereale L.), legume–rye, and mustard was determined in December to February or March during the first 8 yr of the Salinas Organic Cropping Systems (SOCS) trial focused on high‐value crops in Salinas, CA. By seed weight, legume–rye included 10% rye, 35% faba bean (Vicia faba L.), 25% pea (Pisum sativum L.), 15% common vetch (V. sativa L.), and 15% purple vetch (V. benghalensis L.); mustard included 61% Sinapis alba L., and 39% Brassica juncea Czern. Cover crops were fall planted at 1x and 3x seeding rates (SR); 1x SR were 90 (rye), 11 (mustard), and 140 (legume–rye) kg ha−1. Vegetables followed CC annually. Early‐season NA was greatest in mustard. Nitrogen accumulation increased more gradually through the season in legume–rye than in other CC. Final NA (kg ha−1) was lower in rye (110) and mustard (114), than legume–rye (151), and varied by year. During December, SR increased NA in legume–rye by 41% but not for the other CC. Legumes contributed 36% of final NA in legume–rye, presumably from N scavenging and biological fixation. Nitrogen accumulation was highly correlated with shoot dry matter of legume–rye but not of rye or mustard. Seed costs per kg of NA were more than two times higher for legume–rye than rye and mustard. We conclude that high SR are necessary to hasten early season NA and minimize N leaching potential in legume–rye mixtures.
Improved Descriptions of Herbaceous Perennial Growth and Residue Creation for RUSLE2
Authors: Dabney S. M. , Yoder D. C.
Published: June 2012

Earlier versions of the Revised Universal Soil Loss Equation, version 2 (RUSLE2) calculated vegetative residue production only during periods of canopy decline or in response to management operations. This resulted in underestimation of residue amounts and overestimation of soil erosion from pasture and hay lands. To solve this problem, new vegetation routines were implemented in RUSLE2. These modifications were designed to better reflect the amount of residue added by perennial vegetation during its growth and to make it is easier to model haying and grazing scenarios. The new routines were based on the assumption that all unharvested aboveground biomass growth will die after its life span is reached, and this biomass will be added to a standing residue pool. Trained specialists can define the characteristics of a vegetation assemblage in terms of total annual potential production under good management, monthly production percentages reflecting expected fertility and irrigation levels, average vegetation lifespan, maximum canopy height, cutting height for optimal yield, and the tendency of the vegetation to thicken at lower heights (form a sod) in response to repeated defoliations. Users will specify actual harvest management and an underlying model predicts plant growth responses in terms of the amount of harvested forage and the amount of above‐ and belowground residues returned to the soil. The USDA‐NRCS is developing extensive databases so that the new version of RUSLE2 will allow erosion estimates to be a factor considered as part of forage and grazing planning.
Hairy Vetch Varieties and Bi‐Cultures Influence Cover Crop Services in Strip‐Tilled Sweet Corn
Authors: Brainard Daniel , Henshaw Ben , Snapp Sieglinde
Published: June 2012

Hairy vetch (Vicia villosa Roth) cover crops provide a wide array of ecosystem services including erosion protection, weed suppression, and N fixation. However, adoption has been hindered by risks including overwinter mortality and regrowth following mowing or crimping. Early‐flowering vetch varieties and mixed stands of vetch and cereal rye (Secale cereale L.) have the potential to reduce these risks, but little is known about their impact on N fixation. In field trials in Central Michigan, two early‐flowering hairy vetch varieties (Purple Bounty and Purple Prosperity) and one later‐flowering variety (‘Oregon’) were grown alone and in mixtures with cereal rye, prior to strip‐tilled sweet corn (Zea mays L. var. rugosa). Vetches grown in mixture with rye had equal or greater overwinter survival and earlier flowering than vetches grown in monoculture. Nitrogen fixation of early‐flowering varieties was not affected by mixture with rye. However, N fixation of Oregon was lower when grown in monoculture than when grown in mixture in 2009. Purple Bounty and Purple Prosperity flowered earlier than Oregon, exhibited comparable survival, and had equal or greater levels of N fixation. Despite differences in the timing of flowering, there were no differences in regrowth of hairy vetch following mowing. Nor were any differences in sweet corn yield or quality detected. These results demonstrate that rye–vetch mixtures can increase overwinter survival, accelerate flowering, and increase N fixation relative to vetch monocultures. Observed varietal differences in flowering time, N fixation, and response to bicultures may be exploited to optimize cover crop use in agroecosystems.
Nitrogen Dynamics in Irrigated Forage Systems Fertilized with Liquid Dairy Manure
Authors: Geisseler Daniel , Lazicki Patricia A. , Pettygrove G. Stuart , Ludwig Bernard , Bachand Philip A. M. , Horwath William R.
Published: June 2012

Optimal manure management that ensures adequate crop nutrition while avoiding pollution problems requires estimates of manure N availability. The present study was performed in the San Joaquin Valley (California) on three dairy forage production fields where liquid manure is applied together with flood irrigation water. The objective of this study was to determine the fate of manure N by combining field measurements with model simulations using the Root Zone Water Quality Model (RZWQM). The average annual N application to corn (Zea mays L.) and winter forage (oat [Avena sativa L.], triticale [× Triticosecale Wittmack], or Sudan grass [Sorghum bicolor (L.) Moench ssp. drummondii (Steud.) de Wet ex Davidse]) was 840 kg N ha−1, while 490 kg N ha−1 was removed with the harvested crops. The irrigation water input to corn ranged from 45 to 128 cm. The RZWQM described crop yield and N uptake well and accurately simulated the seasonal trends in soil moisture and mineral N content in the top 90 cm of the profile; however, the short‐term changes and mineral N estimates for different soil layers were not accurate. For soil nutrient and water dynamics, site‐specific calibration was an essential requirement. The model estimated that between 140 and 320 kg N ha−1 was leached in a 12‐mo period and up to 80 kg N ha−1 was volatilized as NH3, while losses due to denitrification were insignificant in these sandy soils. Field data and model estimates highlight the potential for a more efficient water and N use in the forage systems studied.
Nonstructural Carbohydrate Concentration during Field Wilting of PM‐ and AM‐Cut Alfalfa
Authors: Morin Chantale , Tremblay Gaëtan F. , Bélanger Gilles , Bertrand Annick , Castonguay Yves , Drapeau Raynald , Michaud Réal , Berthiaume Robert , Allard Guy
Published: June 2012

Alfalfa (Medicago sativa L.) cut in the late afternoon has a greater nonstructural carbohydrate (NSC) concentration than AM‐cut alfalfa but this difference might not be maintained during wilting. We monitored NSC concentration of PM‐ and AM‐cut alfalfa during wilting in narrow and wide swaths. Field‐grown alfalfa was cut either at 1800 h (PM) on days without rain (Day 0) or at 0800 h (AM) the following morning (Day 1) in seven growth cycles over 3 yr. Samples taken during wilting were analyzed for NSC (soluble carbohydrates + starch). At cutting, PM‐cut alfalfa had consistently greater NSC concentration [+6 to 54 g kg−1 of dry matter (DM)] than AM‐cut alfalfa. The NSC concentration decreased during wilting at rates that depended on growth cycles (0.2–3.5 g kg−1 DM h−1 on Day 1) but this decline was similar for AM‐ and PM‐cut alfalfa. When cut alfalfa reached 350 g DM kg−1 fresh matter (FM) on Day 1, NSC concentration was greater for PM‐ than for AM‐cut alfalfa (average of 15 with a range of 4–37 g kg−1 DM) and greater for the wide than narrow swaths (average of 7 with a range of 1–11 g kg−1 DM). Photosynthesis continued for 3 h on the morning of AM cutting for both PM‐ and AM‐cut alfalfa until DM concentration reached approximately 350 g DM kg−1 FM. The combination of late PM‐cutting and wilting in wide swaths can be used to increase the NSC concentration of wilted alfalfa.
Screening of Some Cotton Varieties for Allelopathic Potential on Clover Broomrape Germination
Authors: Ma Yongqing , Lang Ming , Dong Shuqi , Shui Junfeng , Zhao Junxin
Published: June 2012

Research on the chemical basis of allelopathy has often been hindered by the complexity of plant and soil matrices, making it difficult to track active compounds. Well‐designed bioassays under controlled environments can be useful in evaluating the allelopathic potential of plants. This paper describes two experiments about the allelopathic potential of cotton (Gossypium hirsutum L.). In the first experiment, root exudates were collected from six common cotton (G. hirsutum L. and G. barbadense L.) varieties grown hydroponically. The cotton (donor plant) root exudates were tested on clover broomrape (Orobanche minor Smith), to determine which variety had the highest allelopathic potential. In the second experiment, the allelopathic potential of 22 soon‐to‐ be‐released cotton varieties was evaluated for clover broomrape using rhizosphere soil and extracts from different plant parts. The results indicated that methanol was a more suitable reagent than distilled water for extracting germination stimulants from cotton plants. There was a significant positive correlation between the rates of clover broomrape germination in the rhizosphere soil treatments and those in the stem extract (r = 0.6018, P < 0.05) and the leaf extract treatments (r = 0.5540, P < 0.05). There was also a significant positive correlation between germination rates in the root extract treatments and the stem extract treatments (r = 0.7237, P < 0.05). In conclusion, the allelopathic potential of cotton can be assayed by observing the germination of clover broomrape seeds treated with cotton stem extracts.
Ad Hoc Modeling in Agronomy: What Have We Learned in the Last 15 Years?
Authors: Affholder F. , Tittonell P. , Corbeels M. , Roux S. , Motisi N. , Tixier P. , Wery J.
Published: June 2012

The “Use and Abuse of Crop Simulation Models” special issue of Agronomy Journal published in 1996 ended with the myth of the universal crop model. Sinclair and Seligman consequently recommended tailoring models to specific problems. This paper reviews the fate of the idea of such ad hoc approaches to crop simulation modeling during the past 15 yr. Most crop modelers have since adhered to the principles formulated by Sinclair and Seligman, but yet their practice faces two major issues: (i) how to define the structure of the model as depending on the question to be addressed (model conceptualization) and (ii) how to minimize efforts in software development (model computerization). Progress in model conceptualization as reported in the literature concerns (i) inferring a conceptual model from what is known of the problem to address, (ii) deriving summary models from comprehensive ones, and (iii) using multivariate methods to analyze the hierarchy of drivers of variability in the variable to be predicted. Considerable effort has been invested in the development of frameworks to facilitate model computerization, and the commercial modeling software is constantly improving. But there are limits in the flexibility permitted by these tools. Acquiring basic skills in coding a model using a scientific programming language is preferred by scientists wishing to keep the fullest understanding and control on their crop models. Connecting the model to commercial database software may facilitate this strategy. However, the computerization issue may still lead to tensions between modeling teams concerning the legitimacy to develop their own model.
Effect of Planting Date on Soybean Growth, Yield, and Grain Quality: Review
Authors: Hu Mengxuan , Wiatrak Pawel
Published: June 2012

Delayed planting date and unfavorable environmental conditions have a negative effect on soybean [Glycine max (L.) Merr.] growth, development, and yield. Changes in photoperiod, temperature, and precipitation with delayed planting affect the duration of vegetative and reproductive stages, number of branches and pods, plant height, leaf area index (LAI), and normalized difference vegetation index (NDVI), and hence the grain yield. Delayed planting can also affect the soybean seed quality by changing the oil and protein content. Environmental factors like extremely high temperature and drought stress, which are often associated with delayed planting, have also a negative effect on plant development and yield. Compared to optimum air temperature, reduction in photosynthetic rate during heat stress decreases seed set and size, and seed yield. Drought stress during reproductive stages reduces carbon dioxide exchange rate (CER), photosynthesis, sugar production, and flow of metabolites to the expanding cells, which increases flower and pod abortion and decreases vegetative growth, duration of the seed filling stage, seed number, and seed size. Generally, the combined effect of photoperiod, temperature, and precipitation with delayed planting most likely contributes to decreased duration of vegetative and reproductive growth stages, reduced photosynthesis and plant growth, and therefore significant reduction in grain yield of soybean.
Diamond Zoysiagrass Golf Green Response to Reduced Light Environments with the Use of Trinexapac‐Ethyl
Authors: Atkinson Jeffrey L. , McCarty Lambert B. , Liu Haibo , Faust Jim , Toler Joe E.
Published: June 2012

A 2‐yr study was conducted to determine the tolerance of a mature Diamond zoysiagrass [Zoysia matrella (L.) Merr.] golf green to reduced light environments (RLE) treated with trinexapac‐ethyl (TE) at 0 and 0.013 kg ha−1 wk−1. Three levels of RLE, 0, 60, and 90%, were imposed to coincide with maximum seasonal growth of zoysiagrass. Plant growth measurements included turf quality (TQ), chlorophyll concentration, clipping yield, and total nonstructural carbohydrates. Zoysiagrass grown in full sunlight and 60% RLE maintained commercially acceptable TQ (≥7) with and without TE throughout Year 1 while 90% RLE treatments fell below an acceptable level 2 mo after study initiation. Sixty percent RLE treatments without TE demonstrated unacceptable TQ during Year 2. Application of TE sustained turf viability in 90% RLE through Year 2. Clipping yield increased in 60% RLE without TE compared to full sunlight treatments. Application of TE to 60% RLE treatments reduced clipping yield 30 to 76% in Year 1. Chlorophyll concentration in 60% RLE treatments was similar 10 wk after RLE implementation compared to full sunlight treatments in Year 1 and higher in Year 2. Total nonstructural carbohydrate concentration of roots, rhizomes, and stolons was similar in full sun and 60% RLE treatments at the end of both years and between 47 and 100% lower in 90% RLE treatments compared to full sun treatments. These results support the use of Diamond zoysiagrass in up to 60% reduced light putting green environments with concurrent use of a gibberellin biosynthesis inhibiting product such as TE.
Species Selection, Pre‐Plant Cultivation, and Traffic Affect Overseeding Establishment in Bermudagrass Turf
Authors: Trappe Jon M. , Richardson Michael D. , Patton Aaron J.
Published: June 2012

It is common for turf managers to overseed bermudagrass [Cynodon spp. (L.) Rich.] in autumn with cool‐season turfgrasses to enhance playing conditions and to provide a green playing surface with desirable color. The objectives of this study were to determine the effect of pre‐plant cultivation technique and post‐establishment traffic on the establishment of five overseeding species into a sward of bermudagrass. Plots were assigned one of three pre‐plant cultivation treatments of aerification, verticutting, or an untreated control. Five cool‐season turfgrasses including annual ryegrass (Lolium multiflorum L.), intermediate ryegrass (L. perenne × L. multiflorum), meadow fescue (Festuca pratensis Huds.), perennial ryegrass (L. perenne L.), and tetraploid perennial ryegrass (L. perenne L. 2n = 4x = 28) were overseeded 24 Sept. 2007, 17 Oct. 2008, and 28 Sept. 2009. Traffic was applied for three consecutive weeks beginning 1, 2, or 4 wk after planting or left untrafficked. Aerification and verticutting applied before seeding improved establishment compared to the untreated control. Perennial ryegrass was consistently among the species with the highest coverage across cultivation methods and traffic timings, while meadow fescue consistently had the poorest coverage across cultivation methods and traffic timings. Traffic initiated 4 wk after planting was more detrimental than traffic initiated 1 or 2 wk after planting. Based on these results, turfgrass managers would have best overseeding establishment by using aerification or verticutting as a pre‐plant cultivation technique and perennial ryegrass as a species.
Forage and Energy Sorghum Responses to Nitrogen Fertilization in Central and Southern Illinois
Authors: Maughan Matt , Voigt Thomas , Parrish Allen , Bollero Germán , Rooney William , Lee D. K.
Published: June 2012

Recently introduced forage and energy sorghums (Sorghum bicolor L. Moench) have potential as cellulosic biofuel feedstocks in the Midwest. The objectives of this study were to evaluate the effect of N fertilization on biomass yield and to determine the relationship between biomass yield and plant height, leaf development, and leaf area index (LAI) on two forage and two energy sorghum hybrids in four central and southern Illinois (IL) environments. Sorghum hybrids were evaluated in Urbana in 2009 under four N rates and in Urbana, Dixon Springs, and Perry in 2010 under five N rates. Forage sorghums harvested twice (summer and fall) annually produced less biomass than the energy sorghums harvested once in the fall both in 2009 and 2010. Averaged across all environments in 2010, maximum biomass yields were 30.1 Mg DM ha−1 for the energy sorghums and 19.2 Mg DM ha−1 for the forage sorghums at the 224 kg N ha−1 application rate. Biomass yields, LAI, and plant‐height responses to N applications were observed up to 150 kg N ha−1 in 2009 and up to 224 kg N ha−1 in 2010. Leaf development was linearly related to growing‐degree days and the average number of fully expanded leaves on the energy sorghum reached 28 in Perry‐10 with the longest growing season. Photoperiod‐sensitive energy and forage sorghums have potential in central and southern IL as bioenergy feedstocks because these grasses continue vegetative growth until late September, and therefore, produce large amounts of biomass.