bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization and Modeling of the Conduction and Switching Mechanisms of HfOx Based RRAM
Authors: Yu Shimeng , Philip Wong H.-S.
Published: February 2014

The conduction and switching mechanism of resistive random access memory (RRAM) is reviewed in this paper. The resistive switching in oxides is generally attributed to the conductive filament (made up of oxygen vacancies) formation and rupture in the oxide due to field assisted oxygen ion migration. As a model system for device physics study, HfOx based RRAM devices were fabricated and characterized. To identify the electron conduction mechanism, various electrical characterization techniques such as I-V measurements at various temperatures, low-frequency noise measurements, and AC conductance measurements were employed. It was suggested that the trap-assisted-tunneling is the dominant conduction mechanism. In order to explore the oxygen ion migration dynamics, pulse switching measurements were performed. An exponential voltage-time relationship was found between the switching time and the applied voltage. To obtain a first-order understanding of the variability of resistive switching, a Kinetic Monte Carlo (KMC) numerical simulator was developed. The generation/recombination/migration probabilities of oxygen vacancies and oxygen ions were calculated, and the conductive filament configuration was updated stochastically according to those probabilities. The KMC simulation can reproduce many experimental observations in the DC I-V sweep, pulse switching, endurance cycling, and retention baking, etc. The tail bits in the resistance distribution are attributed to the oxygen vacancy left over in the gap region due to a competition between the oxygen vacancy generation and recombination. To enable circuit and system development using RRAM, a compact device model was developed. The compact model, implemented in MATLAB, HSPICE, and Verilog-A, which can be employed in many commonly available circuit simulators using the SPICE engine.
Housing development erodes avian community structure in U.S. protected areas
Authors: Wood Eric M. , Pidgeon Anna M. , Radeloff Volker C. , Helmers David , Culbert Patrick D. , Keuler Nicholas S. , Flather Curtis H.
Published: February 2014

Protected areas are a cornerstone for biodiversity conservation, but they also provide amenities that attract housing development on inholdings and adjacent private lands. We explored how this development affects biodiversity within and near protected areas among six ecological regions throughout the United States. We quantified the effect of housing density within, at the boundary, and outside protected areas, and natural land cover within protected areas, on the proportional abundance and proportional richness of three avian guilds within protected areas. We developed three guilds from the North American Breeding Bird Survey, which included Species of Greatest Conservation Need, land cover affiliates (e.g., forest breeders), and synanthropic species associated with urban environments. We gathered housing density data for the year 2000 from the U.S. Census Bureau, and centered the bird data on this year. We obtained land cover data from the 2001 National Land Cover Database, and we used single‐ and multiple‐variable analyses to address our research question. In all regions, housing density within protected areas was positively associated with the proportional abundance or proportional richness of synanthropes, and negatively associated with the proportional abundance or proportional richness of Species of Greatest Conservation Need. These relationships were strongest in the eastern forested regions and the central grasslands, where more than 70% and 45%, respectively, of the variation in the proportional abundance of synanthropes and Species of Greatest Conservation Need were explained by housing within protected areas. Furthermore, in most regions, housing density outside protected areas was positively associated with the proportional abundance or proportional richness of synanthropes and negatively associated with the proportional abundance of land cover affiliates and Species of Greatest Conservation Need within protected areas. However, these effects were weaker than housing within protected areas. Natural land cover was high with little variability within protected areas, and consequently, was less influential than housing density within or outside protected areas explaining the proportional abundance or proportional richness of the avian guilds. Our results indicate that housing development within, at the boundary, and outside protected areas impacts avian community structure within protected areas throughout the United States.
Nitrogen fixation strategies can explain the latitudinal shift in nitrogen‐fixing tree abundance
Authors: Menge Duncan N. L. , Lichstein Jeremy W. , Ángeles-Pérez Gregorio
Published: February 2014

The rarity of symbiotic nitrogen‐fixing trees in higher‐latitude compared to lower‐latitude forests is paradoxical because higher‐latitude soils are relatively N poor. Using national‐scale forest inventories from the United States and Mexico, we show that the latitudinal abundance distribution of N‐fixing trees (more than 10 times less abundant poleward of 35° N) coincides with a latitudinal transition in symbiotic N‐fixation type: rhizobial N‐fixing trees (which are typically facultative, regulating fixation to meet nutritional demand) dominate equatorward of 35° N, whereas actinorhizal N‐fixing trees (typically obligate, maintaining fixation regardless of soil nutrition) dominate to the north. We then use theoretical and statistical models to show that a latitudinal shift in N‐fixation strategy (facultative vs. obligate) near 35° N can explain the observed change in N‐fixing tree abundance, even if N availability is lower at higher latitudes, because facultative fixation leads to much higher landscape‐scale N‐fixing tree abundance than obligate fixation.
Dimensions of biodiversity in Chesapeake Bay demersal fishes: patterns and drivers through space and time
Authors: Lefcheck Jonathan S. , Buchheister Andre , Laumann Katie May , Stratton Mark A. , Sobocinski Kathryn L. , Chak Solomon T. C. , Clardy Todd R. , Reynolds Pamela L. , Latour Robert J. , Duffy J. Emmett
Published: February 2014

Biodiversity has typically been described in terms of species richness and composition, but theory and growing empirical evidence indicate that the diversity of functional traits, the breadth of evolutionary relationships, and the equitability with which individuals or biomass are distributed among species better characterize patterns and processes within ecosystems. Yet, the advantages of including such data come at the expense of measuring traits, sequencing genes, and counting or weighing individuals, and it remains unclear whether this greater resolution yields substantial benefits in describing diversity. We summarized a decade of high‐resolution trawl data from a bimonthly trawl survey to investigate spatial and seasonal patterns of demersal fish diversity in the Chesapeake Bay, USA, with the goal of identifying areas and times of mismatch between different dimensions of diversity, and their response to environmental forcing. We found moderate to strong positive relationships among all metrics of diversity, and that functional and phylogenetic differences were well‐reflected in an index derived from taxonomic (Linnaean) hierarchy. Compared with species richness and species diversity, functional, phylogenetic, and taxonomic indices peaked later in the year, which was a consequence of the distribution of biomass among functionally and evolutionarily divergent species. Generalized additive models revealed that spatial, temporal, and environmental variables explained roughly similar proportions of deviance across all aspects of diversity, suggesting that these three factors do not differentially affect the functional and phylogenetic aspects of community structure. We conclude that an index of diversity derived from taxonomic hierarchy served well as a practical surrogate for functional and phylogenetic diversity of the demersal fish community in this system. We also emphasize the importance of evenness in understanding diversity patterns, especially since most ecological communities in nature are dominated by one or few species.
Violence, Victimization, Criminal Justice Involvement, and Substance Use Among Drug-Involved Men
Authors: Golder Seana , Logan TK
Published: February 2014

This research identified three subgroups of drug-involved men based on severity of self-reported violence perpetration against intimate or nonintimate partners among a sample of 148 men selected from a subsample of participants in the Kentucky National Institute on Drug Abuse (NIDA) AIDS Cooperative Agreement. Men in the No Violence group accounted for approximately 19% of the total respondents, men in the Moderate Violence Severity and Extreme Violence Severity groups comprises 56% and 25% of the sample, respectively. Men in the Extreme Violence Severity group experienced significantly more psychological victimization as children and more frequent physical childhood abuse than did their peers. Men in the Extreme Violence Severity group reported having earlier involvement in the criminal justice system and lawbreaking behavior; they also reported higher frequency of marijuana and crack use. Implications for treatment and future research are presented.
TPACK Revisited: A Systemic Perspective on Measures for Predicting Effective Integration of Innovative Technologies in School Systems
Authors: Avidov-Ungar Orit , Eshet-Alkalai Yoram
Published: February 2014

TPACK (Technology Pedagogy Content Knowledge) is currently considered one of the most useful frameworks for describing the types of knowledge that teachers should master in integrating technologies effectively in their teaching. According to the TPACK framework, these types of knowledge consist of technological knowledge (TK), pedagogical knowledge (PK), and content knowledge (CK). This article suggests improving the authenticity and the holistic nature of the TPACK framework by (a) adding a new aspect (the affective aspect, which involves teachers’ attitudes toward change) and (b) elaborating on the systemic-organizational aspect (associated with the teachers’ perception of school as a learning organization) and the cognitive aspect (related to the cognitive skills required for effective use of educational technologies), which are not discussed in enough detail in TPACK.
The Cliques Participation Index (CPI) as an Indicator of Creativity in Online Collaborative Groups
Authors: Mazzoni Elvis
Published: February 2014

After introducing the networked flow as a collective creativity process, this article analyzes whether certain social network analysis (SNA) indices could be possible predictors of the social structures’ collective creativity. An empirical study was conducted in which online collaborative groups of adults on a postgraduate course interacted by a web platform to achieve a shared objective. The groups’ final products were evaluated on their originality and transferability, and these were then compared to the groups’ collective activity parameters. Final results show that the Cliques Participation Index (CPI), purposely created for this study, is a potential predictor in the groups’ collective creativity.
Effects of Irrigation, Cultivar, and Plant Density on Cotton Within‐Boll Fiber Quality
Authors: Feng Lu , Bufon Vinicius B. , Mills Cory I. , Hequet Eric , Bordovsky James P. , Keeling Wayne , Boman Randy , Bednarz Craig W.
Published: February 2014

This study was designed to determine how within‐boll fiber quality of cotton (Gossypium hirsutum L.) is affected through irrigation, cultivar, and plant density management. Field experiments were conducted in 2006 and 2007 using two contemporary cultivars, arranged in a split‐split plot design with two irrigation rates (6.33 and 4.32 mm d−1) as the main plot, plant density (79,071; 128,490; 197,677 plants ha−1) as the subplot, and cotton cultivar (FM9063B2RF and ST4554B2RF) as the subsubplot. Plants from 3 m of one row from each plot were hand harvested by fruiting position. First fruiting position bolls from main‐stem nodes 9 and 14 were hand harvested by seed position and ginned separately for Advanced Fiber Information System (AFIS) fiber quality analysis. Increased irrigation generally increased fiber length and upper quartile length, and decreased fineness and maturity ratio. Irrigation effects were greater on fiber length and maturity ratio at seed positions close to the apex of the locule. Increased plant density reduced both fineness and maturity ratio. The cultivar FM9063B2RF produced longer, more mature, and finer fibers than the ST4554B2RF. The overall lowest fiber quality (i.e., shorter and less mature fibers) occurred at seed positions close to the apex of the locule. The superior fiber quality (i.e., longer and more mature fibers) was from the middle to the base of the locule. Abundant rainfall diminished the effects of irrigation on fiber quality.
Nitrogen Requirements for Ethanol Production from Sweet and Photoperiod Sensitive Sorghums in the Southern High Plains
Authors: Tamang P. L. , Bronson K. F. , Malapati A. , Schwartz R. , Johnson J. , Moore‐Kucera J.
Published: February 2014

Sorghum (Sorghum bicolor L. Moench) has high water use efficiency, and is therefore widely cultivated in the Southern High Plains (SHP). Interest in sorghums for biofuel feedstock has increased recently as ethanol demand expands. Unlike grain sorghum, little data are available on N fertilizer requirements for ethanol production from sweet or forage sorghum production. Our objective was to compare ethanol yields and determine optimal N fertilizer needs for ethanol production from sweet sorghum and photoperiod sensitive (PPS) sorghum with limited irrigation in the SHP. Nitrogen fertilizer rates from 0 to 168 N kg ha−1 were tested on four sorghum cultivars (two sweet and two PPS) on Acuff sandy clay loam near Lubbock, TX in 2008 and 2009. Total dry matter (TDM) yields averaged 13 Mg ha−1 across years, cultivars, and N rates. Nitrogen fertilizer response in TDM was observed only in 2009, but bagasse yields responded to N fertilizer in both years. Cellulosic ethanol yields were greater with PPS sorghums than with sweet sorghums in both years. However, total ethanol yields were greater with sweet sorghums than PPS sorghums. Cellulosic ethanol and total ethanol yields responded to N in 2009 only. High preplant soil NO3 in 2008 apparently precluded TDM and ethanol yield response to N fertilizer. The optimum agronomic N fertilizer rate for ethanol and TDM across all four sorghums was 108 kg ha−1 respectively in 2009. The optimum N fertilizer rate for maximum profit with $ 0.70 kg N−1 and $.50 L−1 ethanol was 101 kg ha−1
Association of “Greenness” in Corn with Yield and Leaf Nitrogen Concentration
Authors: Rorie Robert L. , Purcell Larry C. , Mozaffari Morteza , Karcher Douglas E. , King C. Andy , Marsh Matthew C. , Longer David E.
Published: February 2014

Efficient use of N fertilizer has become crucial due to fertilizer costs and the impact of excessive N on the environment. Diagnostic tools for estimating plant N status have an important role in reducing N inputs while maintaining yield. The objective of our study was to quantify corn (Zea mays L.) leaf greenness with a digital camera and image‐analysis software and establish the relationship with yield, leaf N concentration, and chlorophyll meter (or SPAD, soil plant analysis development) values. In 2008 and 2009, field experiments were conducted at five sites with N treatments ranging from 0 to 336 kg N ha−1 At tasseling, the ear leaf was sampled for color analysis and SPAD measurements, and then analyzed for total N. Hue, saturation, and brightness (HSB) values from digital images were processed into a dark green color index (DGCI), which combines HSB values into one composite number. Including calibration disks in images and changing the background color in photographs to pink greatly improved DGCI precision in 2009 over 2008. There was a close relationship (typically r2 ≥ 0.70) of SPAD and DGCI with leaf N concentration. Within a location, yield increased linearly in most cases with both SPAD (average r2 = 0.79) and DGCI (average r2 = 0.78). Digital‐image analysis was a simple method of determining corn N status that has potential as a diagnostic tool for determining crop N needs.
Parameterization and Evaluation of Predictions of DSSAT/CANEGRO for Brazilian Sugarcane
Authors: Marin Fabio R. , Jones James W. , Royce Frederick , Suguitani Carlos , Donzeli Jorge L. , Filho Wander J. Pallone , Nassif Daniel S.P.
Published: February 2014

The DSSAT/CANEGRO model was parameterized and its predictions evaluated using data from five sugarcane (Saccharum spp.) experiments conducted in southern Brazil. The data used are from two of the most important Brazilian cultivars. Some parameters whose values were either directly measured or considered to be well known were not adjusted. Ten of the 20 parameters were optimized using a Generalized Likelihood Uncertainty Estimation (GLUE) algorithm using the leave‐one‐out cross‐validation technique. Model predictions were evaluated using measured data of leaf area index (LAI), stalk and aerial dry mass, sucrose content, and soil water content, using bias, root mean squared error (RMSE), modeling efficiency (Eff), correlation coefficient, and agreement index. The Decision Support System for Agrotechnology Transfer (DSSAT)/CANEGRO model simulated the sugarcane crop in southern Brazil well, using the parameterization reported here. The soil water content predictions were better for rainfed (mean RMSE = 0.122 mm) than for irrigated treatment (mean RMSE = 0.214 mm). Predictions were best for aerial dry mass (Eff = 0.850), followed by stalk dry mass (Eff = 0.765) and then sucrose mass (Eff = 0.170). Number of green leaves showed the worst fit (Eff = −2.300).The cross‐validation technique permits using multiple datasets that would have limited use if used independently because of the heterogeneity of measures and measurement strategies.
Climate Impacts on Agriculture: Implications for Forage and Rangeland Production
Authors: Izaurralde R. C. , Thomson A. M. , Morgan J. A. , Fay P. A. , Polley H. W. , Hatfield J. L.
Published: February 2014

Projections of temperature and precipitation patterns across the United States during the next 50 yr anticipate a 1.5 to 2°C warming and a slight increase in precipitation as a result of global climate change. There have been relatively few studies of climate change effects on pasture and rangeland (grazingland) species compared to those on crop species, despite the economic and ecological importance of the former. Here we review the literature on responses of pastureland and rangeland species to rising atmospheric CO2 and climate change (temperature and precipitation) and discuss plant and management factors likely to influence pastureland and rangeland responses to change (e.g., community composition, plant competition, perennial growth habit, seasonal productivity, and management methods). Overall, the response of pastureland and rangeland species to increased [CO2] is consistent with the general responses of C3 and C4 vegetation, although exceptions exist. Both pastureland and rangeland species may experience accelerated metabolism and advanced development with rising temperature, often resulting in a longer growing season. However, soil resources will often constrain temperature effects. In general, it is expected that increases in [CO2] and precipitation will enhance rangeland net primary production (NPP) whereas increased air temperatures will either increase or decrease NPP. Much of the uncertainty in predicting how pastureland and rangeland species will respond to climate change is due to uncertainty in future projections of precipitation, both globally and regionally. This review reveals the need for comprehensive studies of climate change impacts on pastureland and rangeland ecosystems that include an assessment of the mediating effects of grazing regimes and mutualistic relationships (e.g., plant roots‐nematodes; N‐fixing organisms) as well as changes in water, carbon, and nutrient cycling.
Intensification of Field Pea Production: Impact on Agronomic Performance
Authors: Lafond G. P. , May W. E. , Holzapfel C. B. , Lemke R. L. , Lupwayi N. Z.
Published: February 2014

Including grain‐legumes in cropping systems contributes to a reduction in greenhouse gas emissions and enhances agronomic and economic performance of cropping systems. The objective was to examine the potential for increasing the frequency of field pea (Pisum sativum L.) (FP) in a spring wheat (Triticum aestivum L.) (W)‐based cropping system. Three crop rotations, continuous pea (C‐Pea), W‐FP, and W‐W‐FP, were evaluated over a 10‐yr period (1998–2007) at Indian Head, SK. During the FPphase of C‐Pea and W‐FP, three starter N rates (5, 20, 40 kg N ha−1) were applied. One rate of N (80 kg N ha−1) was used in W. Rotation and N had similar effects on plant densities in either crop. Field pea grain yields were 25% lower with C‐Pea than W‐FP or W‐W‐FP but similar between W‐FP and W‐W‐FP. Starter N had some effect on FP grain yields at the higher N rate in W‐FP but not C‐Pea. Spring wheat grain yields were 3% greater on FP than W stubble. Grain protein in FP was 3.1% higher on C‐Pea than W‐P or W‐W‐FP while grain protein in W was 1 g kg−1 higher on FP than W stubble. Crop water use efficiency in FP and W was not affected by crop rotation. Based on the results of this study, we conclude that the frequency of FP in cropping systems in the subhumid and semiarid areas can be increased intermittently with only a 1‐yr cereal break between FP crops when combined with proper integrated crop management practices.
Winter Rye Cover Crop Management Influences on Soil Water, Soil Nitrate, and Corn Development
Authors: Krueger Erik S. , Ochsner Tyson E. , Porter Paul M. , Baker John M.
Published: February 2014

A winter rye (Secale cerealeL.) cover crop can be seeded after corn (Zea maysL.) silage to mitigate some of the environmental concerns associated with corn silage production. Rye can be managed as a cover crop by chemical termination or harvested for forage. A field study was conducted in Morris, MN in 2008 and 2009 to determine the impact of killed vs. harvested rye cover crops on soil moisture and NO3–N, and to monitor the impact of the rye on subsequent corn yield. Corn for silage was seeded either after winter fallow (control), after a rye cover crop terminated 3 to 4 wk before corn planting (killed rye), or after a rye forage crop harvested no more than 2 d before corn planting (harvested rye). Soil moisture after killed rye was similar to the control, but after harvested rye was 16% lower. Available soil NO3–N was decreased after both killed rye (35%) and harvested rye (59%) compared to the control. Corn biomass yield after killed rye was similar to the control, but yield following harvested rye was reduced by 4.5 Mg ha−1Total forage biomass yield (silage + rye) was similar for all treatments. This work demonstrates that the environmental benefits of a winter rye cover crop can be achieved without impacting corn yield, but the later termination required for rye forage production resulted in soil resource depletion and negatively impacted corn silage yield.
Phosphorus Fertilization Responses on Bahiagrass Pastures: Forage Production and Water Quality
Authors: Obour A. K. , Vendramini J. M. B. , Silveira M. L. , Sollenberger L. E. , O'Connor G. A. , Jawitz J. W.
Published: February 2014

The increased cost of fertilizer and concerns about environmental impacts have led to a reduction in P use in grazed pastures in Florida; however, P fertilization may be necessary to sustain bahiagrass (Paspalum notatum Flügge) pastures. This study evaluated the impacts of reduced P fertilization on forage characteristics, soil and leachate P concentrations on bahiagrass pastures during 2007 and 2008. Treatments consisted of three P fertilization levels (0, 5, and 10 kg P ha−1, applied as KH2PO4) arranged in a randomized complete block design with four replicates. Twelve 1.2‐ha bahiagrass pastures were stocked continuously with a fixed stocking rate of two beef heifers [Bos sp; 380 ± 30 kg live weight (LW)] per experimental unit. Forage was sampled at 14‐d intervals for herbage mass (HM), crude protein (CP), and in vitro digestible organic matter (IVDOM) concentrations. Two suction lysimeters were installed at 60‐ and 90‐cm depth to monitor leachate P. Phosphorus fertilization did not affect HM (4.4 Mg ha−1), herbage accumulation rate (HAR, 43 kg ha−1 d−1), CP (94 g kg−1), or IVDOM (500 g kg−1). Tissue P concentrations increased from 1.9 to 2.2 g kg−1 as P fertilization increased from 0 to 10 kg P ha−1 Soil P concentration in the Ap (7 mg kg−1) and Bh horizons (23 mg kg−1) and leachate P concentration (0.06 mg L−1) were not affected by P application. Despite the lack of yield response to P fertilization, P application at levels of 5 and 10 kg P ha−1 showed no impacts on water quality.
Physiological Response of Chinese Cabbage to Intercropping Systems
Authors: Cai Hongjiao , You Minsheng , Ryall Krista , Li Shiyou , Wang Hong-yi
Published: February 2014

The physiological indices of Chinese cabbage(Brassica chinensis L.) grown under different intercropping systems used for this study included total soluble protein content, soluble sugar content, reducing sugar content, nitrate content, and pigment concentration. The objective of the present study is to discover the physiological level changes in Chinese cabbage in intercropping systems. The intercropping systems studied involved Chinese cabbage‐ garlic (Allium sativum L.) (CG), and Chinese cabbage‐lettuce (Lactuca sativa L.) (CL). Chinese cabbage monoculture served as control (CK). Overall, higher mean soluble protein content and nitrate content were found in Chinese cabbage grown in the intercropping systems than those in CK. Significantly higher chlorophyll a content was found in cabbages from CL than CK during the latter half of the growing season. No significant difference in soluble sugar concentrations was found in CG and CL, as compared with CK. Reducing sugar content varied over the growing period of the Chinese cabbage in CG and CL. These results suggest that Chinese cabbage intercropped with noncrucifer plants increase the plant nutrient content.
How Much Does Considering the Cost of Lime Affect the Recommended Level of Nitrogen?
Authors: Tumusiime Emmanuel , Brorsen B. Wade , Mosali Jagadeesh , Biermacher Jon T.
Published: February 2014

Ammonium‐based N fertilizers acidify soils. Lime used to correct soil pH is a substantial cost to producers. Recommendations about the optimal levels of N to apply typically ignore the cost of the lime needed due to N fertilization acidification. This study aimed to determine the effect of considering the cost of lime on recommendations about the optimal level of N. Yield response and soil pH change functions were estimated and used to determine the optimal levels of N and lime. The study also developed a new version of a linear response plateau function that allows the yield plateau to vary by year with respect to N but not soil pH. The stochastic linear response plateau fit the data best. At current input and output prices, considering the cost of lime reduced the optimal level of N by as much as 11.3%, from 168 to 149 kg ha−1 yr−1 The acidification potential due to N fertilizer increased nonlinearly as the N rate increased. Nitrogen acidification appears to be more severe with N application rates above the consumptive potential of the crop than with N that is used by the plant. The timing of N application had no significant effect on forage yield, but splitting N into fall and spring applications significantly reduced acidification due to excess N fertilization. Recommendations of how much N to apply were 149 kg ha−1 yr−1 with a pH of at least 5.88.
Steer Performance, Intake, and Digesta Kinetics of Switchgrass at Three Forage Masses
Authors: Burns J. C. , Fisher D. S. , Pond K. R.
Published: February 2014

Management strategies to accommodate switchgrass (Panicum virgatum L.) in production systems have been reported but impact of variation in forage mass (FM) on animal responses and pasture stands are lacking. This 4‐yr study assessed canopy and stand characteristic and steer (Bos taurus) responses when ‘Kanlow’ switchgrass was continuously and variably stocked to produce Short (S) (10–16 cm), Medium (M) (20–26 cm), and Tall (T) (35–41 cm) canopy heights. From April to mid‐July (Period 1) FM for S, M, and T average 818, 2164, and 3294 kg ha−1, respectively. Canopies had similar in vitro organic matter disappearance (IVOMD) (626 g kg−1), but increased in neutral detergent fiber (NDF) from S (645 g kg−1) to T (665 g kg−1). Diets decreased in IVOMD from S (744 g kg−1) to T (706 g kg−1). Digesta kinetics data were not altered and average daily gain was similar among FM (1.11 kg d−1). From mid‐July to late September (Period 2), FM averaged 465, 1282, and 2388 kg ha−1, respectively, for S, M, and T. Whole canopy IVOMD increased from S (484 g kg−1) to T (538 g kg−1), whereas NDF was not altered (696 g kg−1). Steers selected a diet similar in IVOMD (685 g kg−1) and NDF (667 g kg−1) among FM. Estimates of dry matter intake (kg 100−1 kg body weight) increased from S (1.75) to T (2.54). Tiller density decreased from T to S. Continuously stocked switchgrass at 20 to 40 cm remained vegetative with 1279 tillers m−2 after 3 yr of grazing.
Field‐Grown Bt and non‐Bt Corn: Yield, Chemical Composition, and Decomposability
Authors: Yanni Sandra F. , Whalen Joann K. , Ma Bao-Luo
Published: February 2014

Bt (Bacillus thuringiensis) corn (Zea mays L.) accounted for 74.5% of the corn acreage in eastern Canada in 2009. Reports that Bt corn has greater yield and lignin concentrations than unmodified corn have raised questions about its effect on the soil ecosystem. Our objectives were to evaluate the biomass of field‐grown Bt and non‐Bt corn, the chemical composition of different corn components that remain as residues in the field after harvest, and the effect of the Bt modification on residue decomposition. Nine Bt corn hybrids and their near isolines were field‐grown in 2008 and 2009. Grain and stover yields were measured and leaves, stems, and roots were collected and analyzed for lignin, C, and N concentrations. Stem sections from a Bt/non‐Bt corn pair were buried in the field and sampled periodically during 1 yr. No difference in yield or lignin concentrations due to the Bt gene was noted; however, N concentration in Bt stems was significantly greater than in non‐Bt stems in 1 yr of the 2‐yr study. Leaves had less lignin and a lower C/N ratio than stems and roots in both years. In buried field litterbags, the decline in C/N ratio and mass loss suggests that Bt stems were decomposing more rapidly than non‐Bt stems. We conclude that the Bt gene does not affect the agronomic performance or the chemical composition of corn in fields without herbivory, and that Bt corn residue may be more susceptible to decomposition than non‐Bt corn residue.
Rice Response to Nitrogen Fertilization under Stale Seedbed and Conventional Tillage Systems
Authors: Harrell D. L. , Tubaña B. S. , Lofton J. , Kanke Y.
Published: February 2014

Drill‐seeded, delayed‐flood rice (Oryza sativa L.) using fall‐stale seedbed (FSS) tillage has risen in popularity over the past decade in the southern USA. Nitrogen research in rice has historically focused on conventional tillage (CT). The objective of the current study was to evaluate potential differences in agronomic characteristics, optimal N rate, N uptake, and N fertilizer recovery efficiency (RE) between the FSS and CT rice production systems. Two varieties (‘Catahoula’ and ‘Neptune’), two tillage systems (CT and FSS), and nine N rates (0, 34, 67, 101, 134, 168, 202, 235, and 269 kg ha−1) were evaluated. Rice emerged 4 d earlier and reached 50% heading 2 d later in CT as compared with the FSS; however, grain moisture at harvest was only slightly different between CT (169 kg ha−1) and the FSS (163 kg ha−1). Grain yield was 317 kg ha−1 higher in the FSS as compared with CT. The rate of fertilizer N needed to achieve maximum yield as determined by the linear‐plateau model was 157 and 151 kg ha−1 for the FSS and CT, respectively. Nitrogen RE ranged from 54 to 63% across N rates but was not significantly affected by variety, tillage, N rate, or their interactions. These results validate current state university N recommendations for drill‐seeded, delayed‐flood rice production and suggest that N fertilizer recommendations should not be altered for rice grown using a FSS.
Inorganic Fertilizers after Broiler Litter Amendment Reduce Surplus Nutrients in Orchardgrass Soils
Authors: Netthisinghe Annesly M.P. , Gilfillen Becky , Willian Todd W. , Rowland Naomi S. , Sistani Karamat R.
Published: February 2014

The common producer practice to dispose of broiler litter at high rates to forage crops allow excessive accumulation of soil nutrients. A remediation study was developed to examine if inorganic fertilizer application over the residual fertility of broiler litter would reduce surplus soil nutrients in orchardgrass (Dactylis glomerata L.) soils and to study the resulting biomass production. Three remediation treatments; inorganic fertilizer on antecedent broiler litter at the nitrogen rate (R‐PLN), phosphorus rate (R‐PLP), phosphorus rate with inorganic nitrogen (R‐PLP+N), and inorganic fertilizer (INORG) were tested and results were compared with broiler litter at nitrogen rate (PLN) phosphorus rate (PLP), and phosphorus rate with inorganic nitrogen (PLP+N). Repeated broiler litter application at N rate led to elevate soil P, Cu, and Zn contents >200% from the initial levels. Implementing an alternative inorganic fertilizer application cycle in such soils can reduce P, Cu, and Zn levels respectively by 32 mg P kg−1 yr−1, 1.9 mg Cu kg−1 yr−1, and 2.4 mg Zn kg−1 yr−1 Remediation by inorganic fertilizer application may take at least 5 yr to reduce P, Cu, and Zn levels back to the normal range. In addition, inorganic fertilizer application over broiler litter at N rate can offer similar forage production as inorganic fertilizer and N rate broiler litter amendment. An alternative cycle of inorganic fertilizer application after broiler litter amendment can be recommended as a best management practice to remediate surplus soil nutrients in highly broiler litter impacted soils while assuring high forage production benefits.
Effect of Cytoplasm on the Agronomic Performance of Grain Sorghum Hybrids
Authors: Moran J. L. , Rooney W. L.
Published: February 2014

Hybrid sorghum [Sorghum bicolor (L.) Moench] seed production relies exclusively on cytoplasmic male sterility (CMS) systems and almost all hybrid sorghum seed is produced using the A1 CMS system. However, the reliance on a single CMS system increases the vulnerability of the crop to diseases and stresses that may attack that particular CMS system. Alternative CMS systems have been described and even used on a limited basis for hybrid seed production, but a direct comparison of the agronomic effects of different cytoplasms has not been possible because male‐sterile lines with a common genetic background (and different cytoplasm) were not available. The recent development of isocytoplasmic A‐lines allows more direct comparison of cytoplasmic effect on agronomic performance. The purpose of this study was to determine by means of a set of isocytoplasmic hybrids if cytoplasm per se influences agronomic performance. Twelve hybrid genotypes were created in three different cytoplasms (A1, A2, and A3 for a total of 36 hybrids), and they were evaluated for plant height, days to anthesis, and grain yield at Weslaco and College Station, TX, in 1998 and 1999. As expected, significant differences existed among hybrids for plant height, days to anthesis, and grain yield. Cytoplasm type had no effect on plant height and was of minimal practical effect on days to anthesis, but a significant reduction in yield was observed in A3 cytoplasm hybrids as compared with A1 and A2 cytoplasm hybrids. The specific reason for the reduced yield of A3 hybrids is not known, but seed set data indicated that it was not associated with fertility restoration. The results indicate that hybrids created in A2 cytoplasm yield comparably to the commonly used A1 cytoplasm and therefore, the A2 system will provide a suitable alternative for hybrid seed production should problems be encountered in the A1 CMS system.
Genetic Diversity, Specific Combining Ability, and Heterosis in Tropical Maize under Stress and Nonstress Environments
Authors: Betrán F. J. , Ribaut J. M. , Beck D. , de León D. Gonzalez
Published: February 2014

Estimation of genetic diversity and distance among tropical maize (Zea mays L.) lines and the correlation between genetic distance (GD) and hybrid performance would determine breeding strategies, classify inbred lines, define heterotic groups, and predict future hybrid performance. The objectives of this study were to estimate (i) heterosis and specific combining ability (SCA) for grain yield under stress and non‐stress environments; (ii) genetic diversity for restriction fragment length polymorphisms (RFLPs) within a set of tropical lines; (iii) GD and classify the lines according to their GD; and (iv) correlation between the GD and hybrid performance, heterosis, and SCA. Seventeen lowland, white tropical inbred lines were represented in a diallel study. Inbred lines and hybrids were evaluated in 12 stress and nonstress environments. The expression of heterosis was greater under drought stress and smaller under low N environments than under nonstress environments. A set of DNA markers identifying 81 loci was used to fingerprint the 17 lines. The level of genetic diversity was high, with 4.65 alleles/locus and polymorphism information content (PIC) values ranging from 0.11 to 0.82. Genomic regions with quantitative trait loci (QTL) for drought tolerance previously identified showed lower genetic diversity. Genetic distance based on RFLP marker data classified the inbred lines in accordance with their pedigree. Positive correlation was found between GD and F1 performance (F1), SCA, midparent heterosis (MPH) and high‐parent heterosis (HPH). Specific combining ability had the strongest correlation with GD. Environment significantly affected the correlations between F1, SCA, MPH, and HPH, with lower values of GD revealed in the more stressed conditions.
Genetic Variation and Relationships among Seedling Vigor Traits in Sorghum
Authors: Cisse N'Diaga , Ejeta Gebisa
Published: February 2014

Seedling vigor in sorghum [Sorghum bicolor (L.) Moench] is important for improving stand establishment of the crop, particularly in arid regions and in areas where low soil temperatures prevail at planting time. This study was conducted to examine the genetic variation, heritability, and relationships among seedling vigor traits in a recombinant inbred (RI) sorghum population developed from two contrasting inbreds. One hundred RI lines and their parents [‘SRN39’, an African caudatum and ‘Shan Qui Red’ (SQR), a Chinese kaoliang] were evaluated for seedling vigor in experiments conducted in the field, in an incubator, and in a greenhouse. Data on 100‐kernel weight, visual seedling vigor scores, percentage germination at 12 and 22°C, percentage emergence, seedling height, and shoot dry weight were collected. Genotypic differences were significant for many of these seedling vigor traits. Significant genetic and additive variances were observed for field vigor scores as well as for those traits measured in the more controlled environments. Heritability estimates for visual scores, percentage germination, emergence, and seedling height were high, while those for seedling dry weight were low to medium. Genetic correlation coefficients of visual seedling scores with the different estimates of vigor were significant except for 100‐seed weight. Significant genetic interrelationships were revealed among traits measured in the greenhouse and incubator at 22°C. Visual scores taken in field experiments appeared effective in integrating germination, emergence at high temperatures, and shoot dry weight. The significant additive genetic variances obtained indicate that the superior seedling vigor observed in the kaoliang parent, SQR, can be effectively utilized for improving germination in cold temperature, as well as germination, emergence, seedling growth, and development at optimum temperature.
Mapping Quantitative Trait Loci in Plant Breeding Populations
Authors: Jansen Ritsert C. , Jannink Jean‐Luc , Beavis William D.
Published: February 2014

Applied breeding programs evaluate large numbers of progeny derived from multiple related crosses for a wide range of agronomic traits and for tens to hundreds of molecular markers. This study was conducted to determine how these phenotypic and genetic data could be used for routinely mapping quantitative trait loci (QTLs). With dense maps, haplotype sharing of parents in a certain region is a good indicator for QTL‐allele sharing, albeit not 100% perfect. With this in mind, an approximate and simple method has been developed where ancestral genome blocks in the parents of the crosses can be identified via haplotype analysis and where the effect of a putative QTL is then modeled and estimated per ancestral genome block. A simulation of an early‐generation maize breeding scheme demonstrates the potential of the present approach for QTL detection in existing breeding programs. With this new QTL mapping strategy, the power, precision, and accuracy associated with large numbers of progeny may be attained, inferences about QTLs can be drawn across the breeding program rather than being limited to the sample of progeny from a single cross, and results may be much more valuable for marker‐assisted breeding because the QTLs apply to agronomically challenging situations in the field.
Clustering Environments to Minimize Change in Rank of Cultivars
Authors: Russell W. K. , Eskridge K. M. , Travnicek D. A. , Guillen‐Portal F. R.
Published: February 2014

Crossover interactions occur in evaluation trials when ranks of cultivars change across environments. Determining groups of environments within which crossover interactions are minimized may facilitate making cultivar recommendations. The goal of this research was to test a new approach for determining these environmental groups in which crossover interaction between a pair of cultivars was defined across all environments. The number of groups was based both on reduction in crossover interaction and repeatability of cultivar means within groups. The validity of this procedure was tested on three simulated data sets with known crossover interactions. For each data set, the approach divided the environments into the two groups that minimized crossover interactions. The approach also was applied to yield data from a maize (Zea maysL.) trial in which 59 environments previously had been clustered by a different measure of crossover interaction. Three groups of 12 environments and one group of 23 environments were defined. The previous clustering had identified six clusters. The amount of crossover interaction within the four environmental groups was reduced by 53% from the total crossover interaction in all 59 environments. The results of the clustering depended on whether all pairwise comparisons among cultivars or only the significant crossover interactions among the higher yielding cultivars were used. The latter method was deemed more appropriate when the goal is to recommend specific cultivars for specific groups of environments. Regardless of the approach used, clustering based on crossover interactions only has practical significance if these interactions are repeatable.
Model Selection and Cross Validation in Additive Main Effect and Multiplicative Interaction Models
Authors: dos S. Dias Carlos T. , Krzanowski Wojtek J.
Published: February 2014

The additive main effects and multiplicative interaction (AMMI) model has been proposed for the analysis of genotype–environmental data. For plant breeding, the recovery of pattern might be considered to be the principal objective of analysis. However, some problems still remain with the analysis, notably in selecting the number of multiplicative components in the model. Methods based on distributional assumptions do not have a sound methodological basis, while existing data‐based approaches do not optimize the cross‐validation process. This paper first summarizes the AMMI model and outlines the available methodology for selecting the number of multiplicative components to include in it. Then two new methods are described that are based on a full “leave‐one‐out” procedure optimizing the cross‐validation process. Both methods are illustrated and compared on some unstructured multivariate data. Finally, their applications to analysis of genotype × environment interaction (GEI) are demonstrated on experimental grain yield data. Conclusions of the study are that the “leave‐one‐out” procedure is preferable in practice to either distributionalF‐test or cross‐validation randomization methods, and of the two “leave‐one‐out” procedures the Eastment‐Krzanowski method exhibits the greater parsimony and stability.
Predicting Potential Kernel Set in Maize from Simple Flowering Characteristics
Authors: Lizaso J. I. , Westgate M. E. , Batchelor W. D. , Fonseca A.
Published: February 2014

Accurate prediction of kernel number per plant is critical for yield simulation in maize (Zea mays L.). Model predictions of kernel number generally are based on empirical relationships between final kernel number and carbohydrate supply or plant growth at silking, without regard to flowering dynamics. The objective of this study was to develop a model for predicting kernel set from seasonal dynamics of pollen shed and silk exsertion. Hybrids were planted in isolated plots at four ratios of male fertile (MF) and male sterile (MS) plants. Dynamics of pollen shed in each plot was described by a Gauss curve and by a population index (Pind) derived from the percentage of plants at beginning, maximum, and ending pollen shed. Percentage of plants at silking followed a sigmoid curve, whereas the number of silks exposed daily per ear followed a monomolecular model. Pollen shed and silk exsertion curves were translated to potential kernel set using a published relationship. Excellent agreement was observed between predicted and measured number of florets per hectare available for pollination. The model overpredicted kernel number per hectare at high pollen shed densities. Predicted kernels per hectare were within 5% of actual kernel numbers at low pollen shed densities when delayed development of subapical ears and asynchronous pollination within ears were considered. These results indicate kernel set in maize can be predicted from simple measures of the flowering process. They confirm that kernel set is limited primarily by factors other than pollen amount when all plants in the population are MF.