bluuebunny/crossref_metadata_2025 huggingface dataset:
Ontogeny of digestion in Daphnia: implications for the effectiveness of algal defenses
Authors: DeMott William R. , McKinney Erin N. , Tessier Alan J.
Published: March 2010

Models of feeding and digestion predict that increased body size should result in longer gut passage time and improved assimilation efficiency. We examined the implications of digestion theory for size‐structured interactions in a generalist zooplankton herbivore by studying the relationships between body size, ingestion rate, gut passage time (GPT), assimilation efficiency (AE), and growth rate in a clone of Daphnia pulex feeding on seven taxa of green algae that differed in digestibility. We also tested the effect of varying food concentration on GPT and AE while keeping body size constant. Food quality varied markedly among algal taxa, with mean juvenile growth rates at high food concentrations (1–2 mg/L) ranging from 0.10 to 0.61 d−1. Juvenile growth rate for high food concentrations was highly correlated with juvenile AE (r2 = 0.96), verifying the importance of digestibility for food quality. AE, measured with 14C‐labeled algae, increased with increasing age and body size for each of four digestion‐resistant taxa but did not vary with age and body size for three readily digested algae. GPT decreased with decreasing body size, supporting the hypothesis that shorter GPT in juveniles leads to lower AE for digestion‐resistant resources. Lower food concentrations led to increased GPT and improved AE for juveniles feeding on two digestion‐resistant algae, providing further support for a role of longer gut retention in overcoming digestion defenses. The results suggest that increased abundance of digestion‐resistant food will lead to growth and recruitment bottlenecks for juvenile herbivores, but that the effectiveness of digestion defenses will be decreased when large‐bodied grazers predominate and when low food concentrations result in longer gut passage times. Gut processing constraints may favor either high concentrations of slow‐growing, digestion‐resistant resources or low concentrations of fast‐growing, undefended resources.
Atmospheric nitrogen deposition influences denitrification and nitrous oxide production in lakes
Authors: McCrackin Michelle L. , Elser James J.
Published: March 2010

Microbially mediated denitrification is an important process that may ameliorate the effects of nitrogen (N) loading by permanently removing excess N inputs. In this study, we measured the rate of denitrification and nitrous oxide (N2O) production during denitrification in sediments from 32 Norwegian lakes at the high and low ends of a gradient of atmospheric N deposition. Denitrification and N2O production rates averaged 41.7 and 1.1 μmol N·m−2·h−1, respectively, for high‐deposition lakes. There was no detectable denitrification or N2O production in low‐deposition lakes. Epilimnetic nitrate concentration was strongly correlated with denitrification rate (r2 = 0.67). We also measured the denitrification rate in response to experimental additions of organic carbon, nitrate, and phosphorus. Experimental nitrate additions stimulated denitrification in sediments of all lakes, regardless of N deposition level. In fact, the rate of denitrification in nitrate‐amended treatments was the same magnitude for lakes in both deposition areas. These findings suggest that lake sediments possess considerable capacity to remove nitrate and that this capacity has not been saturated under conditions of chronic N loading. Further, nitrous oxide was nearly 3% of the total gaseous product during denitrification in high‐deposition lakes, a fraction that is comparable to polluted marine sediments. Our findings suggest that, while lakes play an important role in N removal in the landscape, they may be a source of N2O emissions, especially in areas subject to elevated N inputs.
State of emergency: Behavior of gerbils is affected by the hunger state of their predators
Authors: Berger-Tal Oded , Kotler Burt P.
Published: March 2010

Predator–prey interactions are usually composed of behaviorally sophisticated games in which the values of the strategies of foraging prey individuals may depend on those of their predators, and vice versa. Therefore, any change in the behavior of the predator should result in changes to the behavior of the prey. However, this key prediction has rarely been tested. To examine the effects of the predator state on prey behavior, we manipulated the state of captive Barn Owls,Tyto alba, and released them into an enclosure containing Allenby's gerbils,Gerbillus andersoni allenbyi, a common prey of the owls. The owls were significantly more active when hungry. In response, the gerbils altered their behavior according to the state of the owl. When the owl was hungry, the gerbils visited fewer food patches, foraged in fewer patches, and harvested less food from each patch. Moreover, the gerbils kept their foraging bouts closer to their burrow, which reduced the overlap among foraging ranges of individual gerbils. Thus, changes in the state of the predator affect the foraging behavior of its prey and can also mediate competition among prey individuals.
A quantitative analysis of temporal turnover in aquatic species assemblages across ecosystems
Authors: Korhonen Jenni J. , Soininen Janne , Hillebrand Helmut
Published: March 2010

Recent meta‐analyses have shown that beta diversity through space is jointly driven by species traits, geographical gradients, and ecosystem properties. Spatial variation is, however, only one aspect of beta diversity. The other component is variation in species assemblages through time, that is, temporal turnover. We examined the decrease of assemblage similarity in time in aquatic ecosystems in relation to several ecological, physical, and geographical factors using an extensive data set derived from the literature. The data set was first divided into intra‐annual and interannual studies depending on the temporal extent of the studies. Sampling duration was one the most significant variables affecting the degree of temporal turnover, and we found that turnover was faster in studies with shorter temporal extent. Our results further suggested that the rate of temporal turnover increased with increasing ecosystem size, thus contradicting the general species–time–area relationship. Temporal turnover also varied among the ecosystem types: lake assemblages showed faster turnover than stream or marine assemblages in the interannual data set. We found that temporal turnover exhibited large‐scale geographical variation, as there was a latitudinal gradient in turnover. Turnover was faster in the tropics in the intra‐annual data set, but the pattern was reversed in the interannual data set, where turnover was faster at high latitudes. Finally, we found that the degree of temporal turnover was related to organism characteristics, as larger organisms with active mobility showed slower temporal turnover than smaller organisms. Our results suggest that the degree of species turnover in time is jointly driven by several ecological, physical, and geographical factors in aquatic ecosystems and that the turnover is not uniform across taxonomic groups. Our findings have important consequences for understanding how different biotic assemblages track temporal changes in the environment and how resilient assemblages are toward such changes.
Longitudinal analysis of Plantago: adaptive benefits of iteroparity in a short‐lived, herbaceous perennial
Authors: Shefferson Richard P. , Roach Deborah A.
Published: March 2010

Theory suggests that iteroparity may confer greater fitness than semelparity in situations in which temporal environmental variation is high and unpredictable. Variable age‐specific mortality, density dependence, and other factors may also favor iteroparity over semelparity. Here, we empirically test the adaptive benefits of greater numbers of reproductive years in a study of reproductive schedules in an experimental population of a short‐lived polycarpic perennial, Plantago lanceolata. A large experimental population was established that included four cohorts with similar genetic structure. Individuals were censused for mortality, size, and reproduction for seven years. Plants experienced variable numbers of reproductive years, but one or two years were most common (∼46.7% of the population reproduced only once). The probability of flowering at least once prior to death was determined strongly by extrinsic, environmental or intrinsic but environmentally influenced variables, including early‐life size, cohort, and block, but also varied with a number of interactions involving paternal lineage. Maternal effects explained small but significant components of the variance in the number of reproductive years among individuals in each cohort, while paternal effects were significant in only two cohorts. Number of reproductive years contributed significantly to fitness in this system, more so than all other variables tested, although most of the variation in relative fitness may be attributed ultimately to environmental influences. We suggest that the high proportion of each cohort composed of plants reproducing only once may be due to environmental constraints on either growth or size. Such environmental influences, particularly on early life size, may result in small but important indirect effects on fitness.
Metabolic theory and elevational diversity of vertebrate ectotherms
Authors: McCain Christy M. , Sanders Nathan J.
Published: March 2010

The Metabolic Theory of Ecology (MTE) posits that the temperature‐dependent kinetics of metabolism shape broad‐scale patterns of biodiversity. Here we test whether the MTE accounts for patterns of diversity using 102 elevational diversity gradients of reptiles and amphibians. In particular, we examined the support for the two key predictions of the MTE: that the reciprocal of absolute temperature (1/kT) and diversity are linearly related and that the slope of that relationship is −0.65. We also tested two underlying assumptions of the MTE in cases with appropriate data, namely, that abundance is invariant among samples, and that behavioral thermoregulation influences the MTE predictions. We found that few studies supported the predictions of the MTE for the relationship between environmental temperature and elevational diversity using previous methods on individual gradients and using meta‐analysis. The predominant relationship was curvilinear, and the slopes were steeper than predicted. In analyses of individual gradients, only 6% followed the MTE predictions in the strictest application, and 25% in the broadest. We found violations of the assumption of invariant abundances in all five test cases. All four herpetofaunal groups, regardless of behavioral thermoregulatory abilities, demonstrated poor fits to the MTE predictions. Even when arid gradients are removed, ameliorating the potential effects of water limitation, the MTE did not account for herpetofaunal elevational diversity. We conclude that an interplay of factors shapes elevational diversity gradients rather than the simple kinetics of biochemical reactions.
Lognormal distribution of individual lifetime fecundity: insights from a 23‐year study
Authors: Herrera Carlos M. , Jovani Roger
Published: March 2010

Individual variance in lifetime fecundity within populations is a life‐history parameter of crucial evolutionary and ecological significance. However, knowledge of its magnitude and underlying mechanisms in natural populations is biased toward short‐lived taxa. This paper summarizes results of a 23‐year study on a population of the Mediterranean shrub Lavandula latifolia. We document the within‐population pattern of individual variation in instantaneous and lifetime fecundity (as estimated by inflorescence production) and explore the mechanisms producing the lognormal distribution of individual fecundities by means of an individual‐based simulation model. Throughout the study period, a few individuals consistently produced most inflorescences while the majority of plants exhibited moderate‐to‐low fecundities. The shape of yearly distributions of annual fecundities varied little across years, and most annual fecundity distributions did not depart significantly from a lognormal. The distribution of individual lifetime fecundity did not depart from lognormality. Despite the simplicity of the premises of our simulation model, it was remarkably successful at predicting the shapes of fecundity distributions and the early establishment of a persistent fecundity hierarchy. The agreement between model results and empirical data supports the view that multiplicative interactions of randomly varying environmental effects can play a central role in determining individual variation in lifetime fecundity in L. latifolia, and suggests that environmental stochasticity can be decisive in the genesis of strong fecundity hierarchies in long‐lived plants.
GAGES: A stream gage database for evaluating natural and altered flow conditions in the conterminous United States
Authors: Falcone James A. , Carlisle Daren M. , Wolock David M. , Meador Michael R.
Published: March 2010

Stream flow is a controlling element in the ecology of rivers and streams. Knowledge of the natural flow regime facilitates the assessment of whether specific hydrologic attributes have been altered by humans in a particular stream and the establishment of specific goals for stream‐flow restoration. Because most streams are ungaged or have been altered by human influences, characterizing the natural flow regime is often only possible by estimating flow characteristics based on nearby stream gages of reference quality, i.e., gaged locations that are least disturbed by human influences. The ability to evaluate natural stream flow, that which is not altered by human activities, would be enhanced by the existence of a nationally consistent and up‐to‐date database of gages in relatively undisturbed watersheds.

As part of a national effort to characterize stream‐flow effects on ecological condition, data for 6785 U.S. Geological Survey (USGS) stream gages and their upstream watersheds were compiled. The sites comprise all USGS stream gages in the conterminous United States with at least 20 years of complete‐year flow record from 1950–2007, and for which watershed boundaries could reliably be delineated (median size = 578 km2). Several hundred watershed and site characteristics were calculated or compiled from national data sources, including environmental features (e.g., climate, geology, soils, topography) and anthropogenic influences (e.g., land use, roads, presence of dams, or canals).

In addition, watersheds were assessed for their reference quality within nine broad regions for use in studies intended to characterize stream flows under conditions minimally influenced by human activities. Three primary criteria were used to assess reference quality: (1) a quantitative index of anthropogenic modification within the watershed based on GIS‐derived variables, (2) visual inspection of every stream gage and drainage basin from recent high‐resolution imagery and topographic maps, and (3) information about man‐made influences from USGS Annual Water Data Reports. From the set of 6785 sites, we identified 1512 as reference‐quality stream gages. All data derived for these watersheds as well as the reference condition evaluation are provided as an online data set termed GAGES (geospatial attributes of gages for evaluating stream flow).

The complete data sets corresponding to abstracts published in the Data Papers section of the journal are published electronically in Ecological Archives at 〈http://esapubs.org/archive〉. (The accession number for each Data Paper is given directly beneath the title.)
On the application of multilevel modeling in environmental and ecological studies
Authors: Qian Song S. , Cuffney Thomas F. , Alameddine Ibrahim , McMahon Gerard , Reckhow Kenneth H.
Published: March 2010

This paper illustrates the advantages of a multilevel/hierarchical approach for predictive modeling, including flexibility of model formulation, explicitly accounting for hierarchical structure in the data, and the ability to predict the outcome of new cases. As a generalization of the classical approach, the multilevel modeling approach explicitly models the hierarchical structure in the data by considering both the within‐ and between‐group variances leading to a partial pooling of data across all levels in the hierarchy. The modeling framework provides means for incorporating variables at different spatiotemporal scales. The examples used in this paper illustrate the iterative process of model fitting and evaluation, a process that can lead to improved understanding of the system being studied.
Improved estimation of site occupancy using penalized likelihood
Authors: Moreno Monica , Lele Subhash R.
Published: March 2010

When detection or occupancy probability is small or when the number of sites and number of visits per site is small, maximum likelihood estimators (MLE) of site occupancy parameters have large biases, are numerically unstable, and the corresponding confidence intervals have smaller than nominal coverage. We propose an alternative method of estimation, based on penalized likelihood. This method is numerically stable, the estimators have smaller mean square error than the MLE, and associated confidence intervals have close to nominal coverage.
Case Management for Long-Term Conditions: Developing Targeting Processes
Authors: Abell Jessica , Hughes Jane , Reilly Siobhan , Berzins Kathryn , Challis David
Published: March 2010

Intensive case management (ICM) is traditionally targeted at patients with complex needs and exists within a wider service context. Targeting is integral to the efficiency of the service. A process and outcome evaluation of case management was conducted in a large urban area in England between 2007 and 2008. Data from a postal questionnaire, interviews, and resource utilization data of patients within the service are used to explore issues associated with targeting. The study identified various approaches to select appropriate patients. A lack of standardization in assessment was apparent. Reported policies on case allocation, caseload size, and frequency of visiting patients varied. There was little evidence of ICM. Not all patients in receipt of case management admitted to hospital were diagnosed with a specific disease or condition. Few patients were recorded as discharged and transferred to another service. We conclude that measures of targeting often focus only on admission to a service and specific outcomes and suggest that targeting be considered as a series of interconnected processes rather than static indicators.
Geophysical Monitoring Techniques for Underwater Landslide in 1g Models
Authors: Truong Q. Hung , Lee Changho , Cho Gye-Chun , Lee Jong-Sub
Published: March 2010

Underwater landslides along coastal regions can be considerably large and yield many potential hazards. Many laboratory experiments have been carried out by modeling submerged landslides to understand their failure mechanisms and to develop useful design and construction concepts in an attempt to overcome these problems. This paper presents the implementations of three high resolution geophysical techniques including electrical resistance profile, ultrasonic compressional wave reflection imaging, shear wave geotomography, and a pressure-based method to investigate lab-scaled submerged mass movements of layered soil specimens. Electrical resistance profiles of a soil mass obtained by inserting an electrical resistance probe provide the spatial distribution of soil layers. Ultrasonic reflection images based on the acoustic impedance mismatch between materials are applied to detect layers and landslides with sub-millimeter resolution. Pixel-based images of underwater landslides are created by the inversion of the boundary information derived from the travel times of shear waves. The changes of vertical total stress caused by landslides are detected by using flexible stress sensors in the pressure-based method. The experimental results show that the electrical resistance, ultrasonic wave imaging, and total stress change can provide complementary information, and their associations with a shear wave velocity tomography image provide a better understanding of underwater landslides. This study suggests that these geophysical techniques may be effective tools for the investigation of underwater landslides simulated by a shaking table and centrifuge testing.
Geological Structure Investigation of Shallow Layers by the Explosion Seismic Survey Tomographic Technique
Authors: Zhao Zhixin , Xu Jiren
Published: March 2010

The detailed P-wave velocity structure of the surface layers in the sea area off Kyushu, Japan, was analyzed using a three-dimensional (3-D) tomographic method for explosion seismic refraction and reflection surveys. Approximately 1,830 P-wave arrival times received from 15 rounds of explosion seismic surveys were used in the structural analysis of the two-dimensional (2-D) profile. The 3-D pseudo-bending technique, which is a fast algorithm for two point ray tracing, is used in forward modeling. The conjugate gradient (CG) algorithm was used to solve the discrete linearized equation of the travel-time residuals. The velocity structure obtained from the tomographic technique indicates heterogeneity in the lateral and vertical directions for seismic waves within in the study area. The sedimentary layer is thin near the coast and thickens gradually off the coast. The boundary contours of sedimentary layers reveal complicated serpentine curves. Lateral and/or vertical convex and concave structures are prominent in the contours. The scales of some concave and convex anomalous velocity structures are small; anomalous structures on a [Formula: see text] scale were identified. This might imply that a high resolution tomography imaging technique can be introduced in shallow-structure surveys. The explosion seismic survey tomographic technique characterizes the complicated structure, geometry and physical properties of abnormal objects well, and tomographic inversion of the explosion survey is available for detailed geological structure surveys and resource explorations, especially for resources such as oil, gas and minerals in complicated geological conditions. The calculated convergence velocity and stability of the tomography technique are also of a high standard.
Water Stress Effects on Winter Canola Growth and Yield
Authors: Tesfamariam Eyob H. , Annandale John G. , Steyn Joachim M.
Published: March 2010

Canola (Brassica napus L.) is seen as a dryland crop in many parts of the world. In South Africa, there is growing interest in producing canola under irrigation because of its profitability and beneficial disease control characteristics in a rotation system. The objectives of this study were to identify the growth stage most sensitive to water stress and to determine the effect of water stress on crop growth, phenology, seed and oil yield, water use, and seed oil content. A well watered control was compared with treatments stressed during one of the following stages: vegetative, flowering, or seed filling in replicated field studies during 2002 and 2003 at Pretoria, South Africa. Water stress imposed during flowering delayed maturity by 114 growing degree days. In contrast, water stress imposed during seed fill resulted in 127 growing degree days earlier maturity. The well watered control gave the highest value for leaf area index of 8, water use of 709 mm, seed yield of 3831 kg ha−1, and seed oil content of 398 g kg−1 Canola stressed at flowering gave the lowest values for seed yield of 1361 kg ha−1, seed oil content of 340 g kg−1, and water use of 332 mm. Dry matter production per unit water use at seed filling was only a third of its value during the vegetative and flowering stages. Canola seed and oil yield are most sensitive to water stress at flowering and less sensitive during the vegetative and seed‐filling stages.
Effect of Peanut Hull and Pine Chip Biochar on Soil Nutrients, Corn Nutrient Status, and Yield
Authors: Gaskin Julia W. , Speir R. Adam , Harris Keith , Das K. C. , Lee R. Dewey , Morris Lawrence A. , Fisher Dwight S.
Published: March 2010

Pyrolysis is the anaerobic thermal conversion of biomass for energy production. It offers an option of returning carbon and nutrients to the soil while producing energy. The Ultisols in the southeastern United States have inherently low soil organic carbon and fertility, and may benefit from the addition of biochar from pyrolysis. Our objectives were to evaluate the effect of peanut hull and pine chip biochars on soil nutrients, corn (Zea mays L.) nutrient status and yield in a Kandiudult for two growing seasons (2006 and 2007). Experiments for each biochar source were conducted as completely randomized designs with the biochar applied at 0, 11, and 22 Mg ha−1 with and without N fertilizer. Nitrogen in the peanut hull biochar (209 kg ha−1 at 11 Mg ha−1 rate) was not available during the study based on corn tissue concentrations. The peanut hull biochar linearly increased Mehlich I K, Ca, and Mg in the surface soil (0–15 cm). The increased available K was reflected in the plant tissue analysis at corn stage R1 in 2006, but not in 2007. Pine chip biochar decreased soil pH, but had no effect on other nutrients except Mehlich I Ca. In the peanut hull biochar experiment, grain yields decreased at the 22 Mg ha−1 rate in the fertilized treatments. In the pine chip biochar experiment, grain yields decreased linearly with application rate in 2006, but this did not persist in 2007. Overall yield responses to biochar were smaller than expected based on previous studies.
Effect of Nitrogen and Endophytic Bacteria on Biophysical and Spectral Parameters of Wheat Canopy
Authors: Adami M. , Rudorff B. F. T. , Breunig F. M. , Ponzoni F. J. , Galvão L. S. , Moreira M. A. , Freitas J. G. , Sala V. Marino Rodrigues
Published: March 2010

Nitrogen (N) is the primary limiting factor to increase wheat (Triticum aestivum L.) yield in Brazil, and the use of N‐fixing agents might be an alternative to increase wheat production. A field experiment was conducted in 2006 in São Paulo State, Brazil, with three N rates (0, 60, and 120 kg ha−1) and three endophytic bacteria (IAC‐HT‐11, IAC‐HT‐12, and IAC‐AT‐8) to evaluate their combined impact on biophysical (leaf area index [LAI] and grain yield) and spectral parameters (normalized difference vegetation index [NDVI], absorption band parameters) of wheat and to determine the spectral parameters that best correlated with LAI and grain yield. Leaf area index and canopy spectral reflectance measurements were made at jointing, heading, and ripening growth stages for this purpose. The statistical relationships between biophysical and spectral parameters were evaluated within and among the treatments. Statistical results showed that the N rates significantly affected biophysical and spectral parameters. Bacteria inoculation presented a significant effect only on grain yield, which is consistent with results reported in the literature. The NDVI, followed by absorption band parameters PB and AB at 1205 nm, provided the best estimates of LAI and grain yield during the heading stage, indicating that it may be the best stage for remote sensing–based yield mapping.
Skip‐Row Planting and Tie‐Ridging for Sorghum Production in Semiarid Areas of Ethiopia
Authors: Mesfin Tewodros , Brhane Tesfahunegn Gebreyesus , Wortmann Charles S. , Mamo Martha , Nikus Olani
Published: March 2010

Soil water deficits during grain fill have been estimated to reduce sorghum [Sorghum bicolor (L.) Moench] grain production in Ethiopia by 300,000 Mg yr−1 The potential for skip‐row planting and its integration with tie‐ridging was evaluated for increasing sorghum grain yield in Ethiopia. Skip‐row planting is a means of saving soil water for the grain‐fill period while tie‐ridging is intended to improve soil water availability by reducing runoff. The skip‐row treatments were: no skipped rows (S0:0); one planted alternated with one skipped row (S1:1); two planted alternated with two skipped rows (S2:2); and two planted alternated with one skipped row (S2:1). The tillage treatments were flat tillage and tie‐ridging. Eight trials were conducted. Grain yield in northern Ethiopia was 50% more with S2:1 compared with S0:0. There was no grain yield advantage to S1:1 compared with planting all rows and a yield loss with S2:2. In northern Ethiopia, there was also a grain yield increase with tie‐ridging compared with flat tillage and a positive interaction between tie‐ridging and skip‐row planting. Striga [Striga hermonthica (Delile.) Benth. and Striga asiatica (L.) Kuntze] infestation in northern Ethiopia was reduced by 70% through a combination of tie‐ridging, skip‐row planting, and variety choice. Tie‐ridging and skip‐row planting did not result in increased grain yield in central Ethiopia. The results of this research support the use of tie‐ridging and S2:1 planting where serious striga infestation and severe late‐season stress caused by soil water deficits are common such as in northern Ethiopia.
A Risk Analysis of Converting Conservation Reserve Program Acres to a Wheat–Sorghum–Fallow Rotation
Authors: Williams Jeffery R. , Llewelyn Richard V. , Pendell Dustin L. , Schlegel Alan , Dumler Troy
Published: March 2010

This study examines the economic potential of producing a wheat (Triticum aesitivum) and grain sorghum (Sorghum bicolor (L.) Moench) rotation with three different tillage strategies (conventional, reduced, and no tillage) compared with the Conservation Reserve Program (CRP) in a semiarid region. This research uses enterprise budgeting and stochastic efficiency with respect to a function to determine the preferred management strategies under various risk preferences. Yields, input rates, and field operations from an experimental field in western Kansas are used to calculate net returns for each tillage strategy. Although net returns to crop production using reduced tillage and no‐tillage strategies with average crop prices for January 2007 through December 2008 are higher than CRP payments, risk analysis indicates that CRP would be the preferred strategy for more risk‐averse managers. When average crop prices for January 2006 through December 2008 are used, CRP payments are higher than returns from crop production. Based on this analysis, only individuals who are risk‐neutral or slightly risk‐averse would prefer crop production to continue CRP enrollment in this region unless commodity prices reach the historically high levels of late 2007 and early 2008 and remain there.
Chickpea‐Wheat Rotation for Higher Production in a Humid Tropical Region
Authors: Danga B. O. , Ouma J. P. , Wakindiki I. I. C. , Bar‐Tal A.
Published: March 2010

Stagnation in grain production in the developing world has contributed to the current worldwide food crisis. The principle objective of this study was to evaluate the possibility of improving grain production in the tropical humid region by chickpea (Cicer arietinumL.) in rotation with wheat (Triticum aestivumL). A 3‐yr field experiment in Kenya included four short‐rain‐season (SRS) management practices (chickpea green manure [GM], mature chickpea grain crop [CG], tilled fallow [TF], and weedy fallow [WF]), and inorganic N fertilizer at three rates (0, 30, and 60 kg N ha−1). The chickpea treatments decreased SRS water storage at wheat planting by 14 to 16% compared with TF, but this did not affect yield of subsequent wheat. The GM accumulated 77 kg N ha−1yr−1, compared with 42 kg N ha−1yr−1for the CG. The chickpea treatments increased soil available N by 19% and N uptake by wheat by 39% compared with the fallow methods. Inorganic N applications of 60 kg N ha−1increased soil‐available N at 30 d after sowing by 21.4% and N uptake by wheat by 47%. The CG and GM increased the average annual wheat grain yield by 14 and 31% compared with the WF and TF. Inorganic N applications of 30 and 60 kg N ha−1increased wheat grain yield by 20 and 7%, respectively. The combination of GM with 30 kg N ha−1gave the highest wheat grain yield, but CG with 30 kg N ha−1fertilizer was the most profitable practice.
Economic Profitability of Sustained Application of Swine Lagoon Effluent and Beef Feedlot Manure Relative to Anhydrous Ammonia in the Oklahoma Panhandle
Authors: Park Seong Cheol , Vitale Jeffrey , Turner Jason Clemn , Hattey Jeffory A. , Stoecker Art
Published: March 2010

With the rapid growth of swine (Sus scrofa domestica) production in the Oklahoma Panhandle, animal waste management has become a growing concern. Field experiments were conducted to evaluate the long‐term effects of equivalent nitrogen rates of swine lagoon effluent (SE), beef manure (BM), and commercial fertilizer on the yield and economic returns of irrigated corn (Zea mays L.) grown on calcareous Gruver silt loam soil (fine, mixed, superactive, mesic Aridic Paleustoll) near Goodwell, Oklahoma. A randomized, complete‐block, split‐plot design with three replications was used to test the main effects of N source (NS) and equivalent N application rates (NR) of 56, 168, and 504 kg N ha−1 Both BM and SE generated significantly (P < 0.05) higher corn yields than anhydrous ammonia (AA) across the main effect of NS. Greater separation of mean corn yields was found among NS as the equivalent NR rate was increased from 56 to 504 kg N ha−1 with the following rankings (P < 0.05): AA = BM = SE at 56 kg N ha−1, BM = AA ≥ SE at 168 kg N ha−1, and SE > BM > AA at 504 kg N ha−1 Both SE and BM generated significantly (P < 0.05) higher economic returns than AA. The highest ranked alternatives of economic returns were generated by SE×504 and BM×168. Results indicate that SE and BM can be economically viable substitutes for commercial fertilizer, bringing higher yields and economic benefits to producers in the Oklahoma Panhandle.
The Pattern of Grain Yield Response of Normal and Quality Protein Maize Cultivars in Stress and Nonstress Environments
Authors: Badu‐Apraku B. , Lum A. Fontem
Published: March 2010

Maize (Zea mays L.) cultivars combining high grain yield with elevated levels of lysine, tryptophan, and desirable endosperm modification, could reduce food insecurity and malnutrition in West and Central Africa (WCA). Sixteen early‐ and nine extra‐early‐maturing quality protein maize (QPM) and normal cultivars were evaluated under Striga hermonthica (Del.) Benth infestation and Striga‐free environments in Nigeria from 2006 to 2008 to identify stable and high yielding cultivars. The extra‐early normal maize cultivars 2000 Syn EE‐W STR and 99 TZEF‐Y STR, were similar in yield to the QPM versions under both research conditions. While TZEE‐Y Pop STR C4 was superior in grain yield to its QPM version only under Striga‐free conditions, TZEE‐W Pop STR C4 significantly outyielded the QPM version, under both test conditions and was superior in Striga resistance. In the early maturity group, TZE‐W DT STR C4 outyielded the QPM version by 21% under Striga infestation and by 10% when Striga‐free. In contrast, the QPM cultivar 98 Syn WEC STR QPM C0 outyielded the normal endosperm version by 31% when Striga‐infested. GGE‐biplot analysis demonstrated that two extra‐early and three early maturing cultivars had outstanding performance in both research environments. TZEE‐W Pop STR QPM C0 and EV DT‐W 99 STR QPM C0 were high‐yielding and stable when Striga‐infested while TZE‐Y Pop DT STR C4, TZE‐W Pop DT STR C4, and TZE‐Y Pop STR QPM C0 were superior when Striga‐free. The QPM cultivars with grain yield performance and Striga resistance comparable or superior to those of their normal endosperm versions have been developed in our program.
A New Decay Series for Organic Crop Production
Authors: Endelman Jeffrey B. , Reeve Jennifer R. , Drost Daniel T.
Published: March 2010

For organic farmers who use manure or compost to maintain soil fertility, a pressing question is how much should be applied. Although many factors influence this decision, an important consideration is that manure and compost continue to fertilize for many years after their application. In conventional agriculture, the carry‐over effects of manure have traditionally been quantified in terms of N fertilizer equivalents, that is, through a decay series. Nitrogen decay series may also be used by organic farmers trying to meet N fertilizer recommendations with manure and/or compost. However, this creates an unsustainable paradigm for organic fertility management because N fertilizer equivalency experiments cannot be conducted on organically certified land. We propose a new type of decay series compatible with organic regulations in which the carry‐over effects of manure/compost are measured, not against N fertilizer, but against new applications of the amendment. The result is a decay series in manure/compost equivalents, which, although conceptually straightforward, is not as readily estimated as a N decay series. The methodological challenges of this approach were explored using data from a continuous corn (Zea mays L.) system fertilized with manure slurry. Regression analysis revealed that 1 unit of manure slurry had the same effect on yield as 0.21, 0.16, and 0.13 units of new slurry after 1, 2, and 3 yr, respectively. By quantifying the nutritive and non‐nutritive carry‐over effects of manure/compost, this new decay series has the potential to fully credit organic matter in fertility planning.
Culture of Seashore Mallow under Different Salinity Levels Using Plastic Nutrient‐Rich Matrices and Transplantation
Authors: Zhou Guisheng , Xia Yurong , Ma B. L. , Feng Chaonian , Qin Pei
Published: March 2010

Emergence and early seedling growth are critical for establishing reasonable plant population densities under saline stress conditions. An experiment with seashore mallow (Kosteletzkya virginica L.) seedling culture in plastic nutrient‐rich matrices and transplanted into pots filled with soil from a local farm field was conducted under five salinity levels (0, 0.3, 0.6, 0.9, and 1.2%). Emergence, survival, growth, and physiological characteristics were monitored for 45 d after seeding. Increasing salinity levels from 0.3 to 1.2% inhibited seedling growth through the reduction in leaf size, leaf number, and physiological traits. At 45 d after seeding, there was a reduction of 13 to 47% in photosynthesis, 18 to 62% in soluble protein, 6 to 84% in superoxide dismutase activity, and 20 to 81% in root activities, whereas free amino acids increased by 34 to 104%, proline by 18 to 167%, and malondialdehyde by 20 to 220%. The reduction in photosynthesis was mainly associated with the reduction in stomatal conductance. Emergence and survival rates could be maintained at ≥60% at salinity levels ≤0.9%. Our results indicate that seashore mallow could grow in saline soils with seedling culture in nutrient‐rich plastic matrices and transplanted into conventional soils provided that the salinity levels in nutrient‐rich medium and conventional soils are ≤0.9%.
Study on Japanese Cornmint in Mississippi
Authors: Zheljazkov Valtcho D. , Cantrell Charles L. , Astatkie Tess
Published: March 2010

Japanese cornmint (Mentha canadensis L.) is a subtropical essential oil crop grown in Asia and South America. The essential oil of Japanese cornmint is the source for production of crystal (–)‐menthol, which is an important aromatic agent used in various industries. The United States is a major importer and consumer of (–)‐menthol and de‐mentholized oil. Currently there is no production of Japanese cornmint in the United States. A 2‐yr study was conducted in Mississippi to evaluate the effect of N application rates (0, 80, and 160 kg ha−1) and cut (harvest time, with a first cut in July, and a second cut in October) on herbage yields, essential oil content, and composition of two Japanese cornmint genotypes (‘Arvensis 2’ and ‘Arvensis 3’). Both cultivars provided two cuts and comparable herbage and oil yields to literature reports. Generally, N application increased fresh herbage and oil yields relative to the untreated control. Herbage, essential oil, (–)‐menthol, and (–)‐menthone yields were greater from the first cut than from the second for both cultivars. The concentration of (–)‐menthol in the oil of both cultivars was approximately 50% in 2007; however, in 2008 the (–)‐menthol concentration was 67 to 76% in ‘Arvensis 2’ and 73 to 78% in ‘Arvensis 3’. This study demonstrates that Japanese cornmint could be successfully grown in Mississippi and possibly other areas in the southeastern United States with similar environmental conditions.
Tractor‐Based Quadrilateral Spectral Reflectance Measurements to Detect Biomass and Total Aerial Nitrogen in Winter Wheat
Authors: Mistele Bodo , Schmidhalter Urs
Published: March 2010

Spectral measurements can be used to detect the canopy N status and allow locally adjusted N fertilizer application during the growing season. The present study investigates the potential of a tractor‐based field spectrometer with a quadrilateral view optical setup to detect aboveground biomass dry weight and total aerial N in winter wheat (Triticum aestivumL.) in a 3‐yr field experiment. The measuring time and the weather conditions were chosen, to be able to compare instrument performance under various sky conditions (sunny, cloudy, hazy) and at different solar zenith angles. New and known vegetations indices were tested in dense, high‐yielding crop stand (average yields 6–10 Mg ha−1) receiving 0 to 210 kg N ha−1to detect aboveground biomass dry weight and total aerial N. Validations were performed on large calibration areas of 25 m2matching exactly the field of view from the sensor. The results obtained show that strong relationships (R2= 0.90) exist between reflectance indices and total aerial N from the end of tillering at growth stage GS 29 to flowering at GS 71, whereas aboveground biomass dry weight could be detected with aR2of 0.75. A new simple index R780/R740was developed with similar potential to the red edge inflection point (REIP). The optical setup allows for measurements to be highly independent of time of day and sky conditions. Consequently the system promises to contribute to improved N management in heterogeneous fields.
Performance of Annual and Perennial Biofuel Crops: Yield during the First Two Years
Authors: Propheter J. L. , Staggenborg S. A. , Wu X. , Wang D.
Published: March 2010

Increasing demand for renewable fuel sources has stimulated the need for alternative biomass crops. A study was conducted to determine grain, stover, total biomass, and estimated ethanol yields of annual and perennial crops at two locations in Kansas in 2007 and 2008. This study included corn (Zea mays L.) grown continuously and rotated with soybean [Glycine max (L.) Merr.]; five sorghum cultivars, brown midrib (bmr), photoperiod sensitive, sweet, and two dual‐purpose forage varieties; and three perennial warm‐season grasses, switchgrass (Panicum virgatum L.), big bluestem (Andropogon gerardii Vitman), and Miscanthus (Miscanthus × giganteus). Corn and sorghum plants were harvested for grain and biomass and sweet sorghum stalks were pressed to extract juices. Perennial grasses were harvested for biomass. Highest grain yields were achieved with corn across both years and locations with yields averaging 10.1 Mg ha−1 Total biomass yields were greatest for sweet sorghum (32.6 and 28.2 Mg ha−1 in 2007 and 2008, respectively) and photoperiod‐sensitive sorghum (26.8 Mg ha−1 in 2007). Sweet sorghum extracted fermentable carbohydrate yields averaged 4.8 Mg ha−1 Perennial grass biomass yields ranged from 7.7 to 12.8 Mg ha−1 in 2008, the second year after establishment. Highest average estimated ethanol yields were achieved with sweet sorghum (9920 L ha−1). These results indicate that the highest total biomass and estimated ethanol yields for renewable fuel production can be achieved from sweet sorghum and that perennial grasses were as productive as annual crops at producing biomass in the first 2 yr after planting.
Biological Significance of Low Weed Population Densities on Sweet Corn
Authors: Williams Martin M.
Published: March 2010

Some weed plants escape current weed management systems in nearly all sweet corn (Zea maysL.) fields. Decisions to target escaped weeds, and justify the added expense, require knowledge of the biological significance of low weed population densities on the crop. The objectives were to (i) quantify giant ragweed (Ambrosia trifidaL.) area of influence (AOI) on sweet corn, and (ii) investigate potential links among giant ragweed AOI and crop growth, development, and yield attributes. All measured crop attributes were influenced by giant ragweed AOI, including plant height near silk emergence (HT), thermal time to silk emergence, green ear mass (GMASS), husked ear mass (HMASS), filled ear length (LENGTH), ear width at midpoint (WIDTH), and kernel moisture (MOIST). Proportion of silked plants declined for sweet corn within 160 cm of giant ragweed, with less than one‐half of the crop plants producing a marketable ear within 42 cm of giant ragweed. Weed interference harmed ear attributes most when crop development was delayed, as evidenced by path analysis of giant ragweed's direct and indirect associations with yield attributes. Even the lowest population density of giant ragweed can be costly, with yield loss estimates ranging from $0.86 to $8.75 per weed plant, depending on crop market type.
Corn Response to Delayed Planting in the Central Great Plains
Authors: Sindelar A. J. , Roozeboom K. L. , Gordon W. B. , Heer W. F.
Published: March 2010

In the central Great Plains, there is growing interest in management options that could improve and stabilize corn (Zea mays L.) production in marginal environments. Limited research exists regarding the practice of delayed planting and its impact in the central Great Plains. Three environments were defined from six location‐years in 2007 and 2008 based on the degree and duration of environmental stress. When planting was delayed from early April to late June grain yields were reduced by 10% in low‐stress environments, increased by 30% with early‐season stress, and decreased by 60% when full‐season stress occurred. In low‐stress and early stress environments, vegetative biomass was greatest for late May to early June planting dates. Leaf area index (LAI) at tassel (VT) also was dependent on planting date, as decreases were not observed in the low‐stress and high‐stress groups until late June planting dates. In the early‐season stress environment, early June planting dates produced the greatest LAI at VT (3.90), and mid‐April planting dates produced the lowest (3.34). These results suggest that scenarios exist where later planting may be a viable alternative for maintaining dryland corn yields in select environments.
Grain Sorghum Yield with Hybrid Advancement and Changes in Agronomic Practices from 1957 through 2008
Authors: Assefa Yared , Staggenborg Scott A.
Published: March 2010

Sorghum [Sorghum bicolor (L.) Moench] grain yield has improved since the deployment of hybrid sorghum in the mid‐1950s. However, information on the contribution of different factors to this yield increase for irrigated and dryland sorghum production is scarce. The objective of the present study was to determine the magnitude of change in irrigated and dryland sorghum yields with hybrid improvement and changes in agronomic practices. Data from selected irrigated and dryland grain sorghum performance trials conducted in Kansas from 1957 to 2008 were analyzed. The mean yield of the highest‐yielding hybrid over years was 9.3 Mg ha−1 at irrigated sites and 5.8 Mg ha−1 at the dryland sites. There was an increase in hybrid yield of nearly 50 kg ha−1 yr−1 in dryland sites over the 52 yr analyzed. Irrigated grain sorghum yields, however, remained unchanged over the same period. Agronomic practices such as planting date, P fertilizer use, and planting density changed over these years but were not found to contribute to increased dryland sorghum yields. Hybrid advancement and increased N fertilizer application were responsible for changes in dryland yields. The yield focus of sorghum hybrid development was effective in dryland sorghum production, likely because of intentional or inadvertent selection of hybrids with better drought tolerance.