bluuebunny/crossref_metadata_2025 huggingface dataset:
Dissolved fraction of standard laboratory cladoceran food alters toxicity of waterborne silver toCeriodaphnia dubia
Authors: Kolts Jason M , Brooks Marjorie L , Cantrell Brittney D , Boese Connie J , Bell Russell A , Meyer Joseph S
Published: May 2008

The biotic ligand model (BLM) for the acute toxicity of cationic metals to aquatic organisms incorporates the toxicity-modifying effects of dissolved organic matter (DOM), but the default parameterization (i.e., assuming 10% of DOM is humic acid) does not differentiate DOM from different sources. We exposed a cladoceran (Ceriodaphnia dubia) to Ag in the presence of DOM from filtered YCT (standard yeast–Cerophyll®–trout chow food recommended by the U.S. Environmental Protection Agency [EPA] for cladocerans), from the Suwannee River (GA, USA; relatively little anthropogenic input), and from the Desjardins Canal in Hamilton (ON, Canada; receives treated municipal wastewater effluent). In all three treatments, the dissolved organic carbon (DOC) concentration was 2 mg/L (the concentration following addition of YCT slurry at the U.S. EPA–recommended volume ratio). The average 48-h median effects concentration (EC50) ratios for dissolved Ag in the presence and absence of DOM [i.e., (EC50 with DOM)/(EC50 without DOM)] were as follows: Suwannee River, 1.6; Desjardins Canal, 2.2; and YCT filtrate, 26.8. Therefore, YCT filtrate provided much more protection against Ag toxicity than that provided by DOM from the surface waters. The major spectral characteristic that differentiated YCT filtrate from the other two types of DOM was a strong tryptophan peak in the excitation–emission matrix for YCT. These results have important implications for interpreting Ag toxicity tests in which organisms are fed YCT, and they suggest BLM-calculated toxicity predictions might be improved by incorporating specific chemical constituents or surrogate indices of DOM. Another component of the protective effect against Ag toxicity, however, might be that the dissolved fraction of YCT served as an energy and/or nutrient source for C. dubia.
The role of biomarkers to assess oil-contaminated sediment quality using toxicity tests with clams and crabs
Authors: Morales-Caselles Carmen , Martín-Díaz María Laura , Riba Inmaculada , Sarasquete Carmen , Valls Tomás Ángel Del
Published: May 2008

A 28-d bioassay was conducted with two invertebrate species with different feeding habits, the clam Ruditapes philippinarum and the shore crab Carcinus maenas. The purpose of the present study was to assess the quality of sediments affected by oil spills in different areas of the Spanish coast. The organisms were exposed to environmental samples of oil-contaminated sediments during four weeks and, after the experiment, a suite of biomarkers of exposure was measured: The phase one detoxification system was assessed by ethoxyresorufin-O-deethylase (EROD) activity; glutathione-S-transferase (GST) is a phase-two detoxification enzyme but also is implicated in oxidative stress events; glutathione peroxidase (GPX), glutathione reductase (GR), and the ferric reducing ability of plasma (FRAP) assay were analyzed to determine the antioxidant activity of the tissues. The biomarker results were correlated with the chemical compounds bound to sediments (polycyclic aromatic hydrocarbons [PAHs], polychlorinated biphenyls [PCBs], Zn, Cd, Pb, Cu, Ni, Co, V) and a principal component analysis was carried out with the purpose of linking all the variables and to detect those contaminated sediments potentially harmful to the biota. Results showed induction of biomarkers in both invertebrate species and significant differences (p < 0.05; p < 0.01) were established among sediments affected by different spills. The use of the selected biomarkers together with the sediment chemical analysis assesses the bioavailability of contaminants and has proven to be a suitable tool to monitor the environmental quality of sediments affected by oil spills.
Morphometric alterations in Mytilus galloprovincialis granulocytes: A new biomarker
Authors: Calisi Antonio , Lionetto Maria Giulia , Caricato Roberto , Giordano Maria Elena , Schettino Trifone
Published: May 2008

Bivalve molluscs, particularly marine mussels, are used widely as sentinel organisms in environmental quality monitoring and assessment. Biochemical and cellular responses to pollutant exposure (i.e., biomarkers) increasingly are investigated in mussel tissues and their measurements largely used in marine environmental monitoring. The aim of the present study was to investigate possible pollutant-induced morphometric alterations in Mytilus galloprovincialis granulocytes in view of future applications as a sensitive, simple, and quick biomarker for monitoring and assessment applications. Granulocyte morphometric alterations were determined by image analysis on Diff-Quick® stained cells. For the first time, the rapid alcohol-fixed Diff-Quick stain protocol, utilized in clinical and veterinary applications for immediate interpretation of histological samples, was shown to be suitable for rapid cytological staining of M. galloprovincialis haemocytes. The present study was carried out in standardized laboratory conditions and further validated in field conditions. Results show consistent pollutant-induced enlargement of mussel granulocytes. This was verified by standardized biomarkers such as metallothionein concentrations in the digestive gland or lysosomal membrane stability in laboratory and field exposures. Results further suggest that the observed morphometric alterations can be used as a biomarker of chemical stress. Because no single biomarker generally is adequate for describing the complexity of effects induced by environmental pollutants on the organisms, we propose that morphometric alterations of granulocytes should be used in a biomarker battery in marine environmental monitoring programs such as Mussel Watch.
Persistence and degradation of maize-expressed vaccine protein, Escherichia coli heat-labile enterotoxin subunit B, in soil and water
Authors: Kosaki Hirofumi , Coats Joel R , Wang Kan , Wolt Jeffrey D
Published: May 2008

Transgenic plants represent an innovative platform for the cost-effective large-scale production of various pharmaceutical proteins. The eventual open-field production of plant-made pharmaceuticals (PMPs) requires risk assessment to determine the potential for harm to the surrounding ecosystem. In the present study, the environmental persistence of a transgenic maize-expressed antigen, Escherichia coli heat-labile enterotoxin subunit B (LTB), was studied under laboratory conditions. To semiquantitatively monitor the persistence of LTB in soil, extraction with a high-salt, high-pH extraction buffer was optimized using the closely homologous Vibrio cholerae enterotoxin subunit B (CTB) as a test substance. The time to dissipation of 50% (DT50) of the extractable fraction of maize-expressed LTB was 4 to 15 d in pond water and 35 to 90 d in soils. Both extraction efficacy and persistence were strongly affected by the matrix type and incubation conditions. In contrast with maize-expressed LTB, the DT50 for bacterially produced LTB and CTB was less than 4 d both in pond water and soil. Although maize-expressed LTB was more stable than bacterially produced analogue, its dissipation was governed by an initial lag, which could be attributed to release from the plant material, followed by rapid decline.
Perfluorinated, brominated, and chlorinated contaminants in a population of lesser black-backed gulls (Larus fuscus)
Authors: Bustnes Jan O , Borgå Katrine , Erikstad Kjell E , Lorentsen Svein-Håkon , Herzke Dorte
Published: May 2008

Protein-bound perfluorinated compounds (PFCs) and lipid-soluble polybrominated diphenyl ethers (PBDEs) and organo-chlorines (OCs) were measured in whole blood from a large number (n = 83) of breeding lesser black-backed gulls (Larus fuscus) caught during two distinct sampling periods in a colony on the coast of northern Norway. We analyzed 14 PFCs (seven were detected in more than 75% of samples), 10 PBDEs (only BDE 47 was detected), and 27 OCs, including 12 polychlorinated biphenyl (PCB) congeners (14 OCs were detected). Median total PFC concentration was higher than median total OC concentration (43 vs 39 ng/g wet wt). Perfluorooctane sulfonate (PFOS) was the dominant PFC (mean relative contribution of PFOS to total contaminant concentration in blood [Σtotal contaminants] was 38%), whereas total PCB (26% of Σtotal contaminants) and p,p′-DDE (2,2-bis(4-chlorophenyl)-1,1-dichloroethene; 13% of Σtotal contaminants) were the dominant OCs. No covariability was found between protein-bound and lipid-soluble compounds; individuals with high concentrations of PFCs did not have high concentrations of OCs or BDE 47. The concentrations of PFCs were lower in birds caught during the late sampling period compared to those of the early period, and females had lower levels of some PFCs compared with males, suggesting that females sequester fluorinated substances into eggs. For lipid-soluble compounds, no significant sex or sampling period differences were found, except that trans-nonachlor, cis-nonachlor, and p,p′-DDE concentrations were lower in birds caught during the late sampling period. The pattern of PFC compounds (relative to PFOS) and lipid-soluble compounds (relative to PCB 153) differed between sampling periods in females but not in males. Finally, PFCs were distributed more uniformly within the population than the lipid-soluble compounds, for which the distributions were strongly negatively skewed.
How subcellular partitioning can help to understand heavy metal accumulation and elimination kinetics in snails
Authors: Gimbert Frédéric , Vijver Martina G , Coeurdassier Michaël , Scheifler Renaud , Peijnenburg Willie J.G.M , Badot Pierre-Marie , de Vaufleury Annette
Published: May 2008

To understand bioaccumulation kinetics of metals within biota inhabiting industrially contaminated soils, toxicokinetic dynamics and subcellular fractionation were carried out with the terrestrial snail Helix aspersa in a long-term (six-month) laboratory experiment. Accumulation and elimination kinetics were determined for Cd, Pb, and Zn in both viscera and foot of snails and were described accurately by one-compartment models. The subcellular fractions were obtained by sequential centrifugations and were analyzed by isolating metal-rich granules, tissue fragments, and cytosolic fractions. Different fractions showed metal-specific binding capacities that might be useful in identifying the biological significance of accumulated metal levels in snails. Cadmium was retrieved mainly from the cytosolic fraction, where it was stored in the long term and not excreted, thus explaining the linear accumulation patterns. Most of the accumulated Pb was found in the granular fraction, and snails appeared able to excrete these concretions, leading to achievement of a steady state in internal Pb body burdens. Significant levels of Pb, however, were retrieved at the end of the depuration phase and retained in the cell debris fraction. Zinc showed affinities for both cytosolic and granular fractions, leading to intermediate uptake and excretion patterns. The dynamics of the different sequestration forms at the subcellular level support the observed kinetics of metal body burdens and, in association with the determination of uptake fluxes, allow precise assessment of metal accumulation in snails.
Abiotic reduction of nitroaromatic contaminants by iron(II) complexes with organothiol ligands
Authors: Naka Daisuke , Kim Dongwook , Carbonaro Richard F , Strathmann Timothy J
Published: May 2008

Complexation of FeII by dissolved and surface-bound ligands can significantly modify the metal's redox reactivity, and recent work reveals that FeII complexes with selected classes of organic ligands are potent reductants that may contribute to the natural attenuation of subsurface contaminants. In the present study, we investigated the reactivity of FeII–organothiol ligand complexes with nitroaromatic contaminants (NACs; ArNO2). Experimental results show that NACs are unreactive in Fe2+-only and ligand-only solutions but are reduced to the corresponding aniline compounds (ArNH2) in solutions containing both FeII and a number of organothiol ligands. Observed reaction rates are highly dependent on the structure of the FeII-complexing ligand, solution composition, FeII speciation, and NAC structure. For two model ligands, cysteine and thioglycolic acid, observed pseudo–first order rate constants for 4-chloronitrobenzene reduction (kobs; 1/s) are linearly correlated with the concentration of the respective 1:2 FeII–organothiol complexes (FeL22−), and kobs measurements are accurately predicted by kobs = kFeL22-[FeL22−], where kFeL22- = 1.70 (±0.59) 1/M/s and 26.0 (±4.8) 1/M/s for cysteine and thioglycolic acid, respectively. The high reactivity of these FeII complexes is attributed to a lowering of the standard one-electron reduction potential of the FeIII/FeII redox couple on complexation by organothiol ligands. The relative reactivity of a series of substituted NACs with individual FeII complexes can be described by linear free-energy relationships with the apparent one-electron reduction potentials of the NACs. Tests also show that organothiol ligands can further promote NAC reduction indirectly by re-reducing the FeIII that forms when FeII complexes are oxidized by reactions with the NACs.
Tenax® extraction as a tool to evaluate the availability of polybrominated diphenyl ethers, ddt, and ddt metabolites in sediments
Authors: de la Cal Agustina , Eljarrat Ethel , Grotenhuis Tim , Barcelo Damià
Published: May 2008

Solid-phase extraction with Tenax® is one of the most used methods for determining the fraction of a pollutant that desorbs rapidly from sediment and thus is available for living beings. In the present study, this technique has been applied to sediment contaminated in the laboratory with polybrominated diphenyl ethers (PBDEs) and dichlorodiphenyltrichloroethane, dichlorodifenyldichloroethylene, and dichlorodifenyldichloroethane (generically, DDXs). The amount of chemical retained in sediment during the time of the experiment fit well with a three-phase exponential desorption model. The ratios between the rapidly desorbing fraction and the fraction desorbed during a fixed time (6 or 24 h) were calculated. The fraction desorbed in 6 h was lower than the rapidly desorbing fraction for most of PBDEs, whereas the fraction desorbed in 24 h exceeded the rapidly desorbing fraction for both groups of compounds. However, variability of these data suggests, when possible, a long time measure of desorption in order to achieve a more accurate estimation. Both the extent and the velocity of desorption were inversely related with the bromination degree and, consistently, with hydrophobicity and molecular size. In this way, low brominated PBDEs and DDXs showed a high availability relative to high brominated PBDEs.
Adsorption of hydrophobic organic compounds onto a hydrophobic carbonaceous geosorbent in the presence of surfactants
Authors: Wang Peng , Keller Arturo A
Published: May 2008

The adsorption of hydrophobic organic compounds (HOCs; atrazine and diuron) onto lampblack was studied in the presence of nonionic, cationic, and anionic surfactants (Triton® X-100), benzalkonium chloride [BC], and linear alkylbenzene sulfonate [LAS]) to determine the effect of the surfactant on HOC adsorption onto a hydrophobic carbonaceous geosorbent. Linear alkylbenzene sulfonate showed an adsorption capacity higher than that of BC but similar to that of Triton X-100, implying the charge property of a surfactant is not a useful indicator for predicting the surfactant's adsorption onto a hydrophobic medium. The results also indicated that the octanol-water partition coefficient (Kow) of a surfactant is not a good predictor of that surfactant's sorption onto a hydrophobic medium. Under subsaturation adsorption conditions (i.e., before sorption saturation is reached), surfactant adsorption reduced HOC adsorption to a significant extent, with the reduction in HOC adsorption increasing monotonically with the amount of surfactant adsorbed. Among the three surfactants, Triton X-100 was the most effective in reducing HOC adsorption, whereas BC and LAS showed similar effectiveness in this regard. Under the same amount of the surfactant sorbed, the reduction in atrazine adsorption was consistently greater than that for diuron because of atrazine's lower hydrophobicity. No significant difference was observed in the amount of the HOC adsorbed under different adsorption sequences. Our results showed that the presence of surfactant can significantly decrease HOC adsorption onto hydrophobic environmental media and, thus, is important in predicting HOC fate and transport in the environment.
Agronomic Performance of Different Pea Cultivars Under Various Sowing Periods and Contrasting Soil Structures
Authors: Vocanson Aurélie , Jeuffroy Marie‐Hélène
Published: May 2008

Yield variability of spring pea (Pisum sativum L.) in farmers' fields is mainly due to soil compaction at sowing and abiotic stresses during the reproductive period. Winter peas flower earlier, and thus should be less sensitive to abiotic stress at the end of the cycle, but because of their sensitivity to frost they must be sown late in autumn when soils are very wet. Pea breeders are working on new winter cultivars that are more resistant to frost and highly sensitive to photoperiod and that could be sown earlier in autumn under better soil conditions. Our aim was to measure crop growth, development, and seed yield of different types of pea cultivars using factorial experiments that evaluated the effect of soil structure, sowing period, and cultivar at two sites in France. Compaction reduced seed yield by 18% at Grignon and 6% at Estrées‐Mons, but had no significant effect on crop development. November sowings resulted in increased seed yield of about 1 t ha−1 at both sites compared with spring sowings, and were associated with larger numbers of reproductive nodes and seeds m−2. Cultivars exhibited contrasting characteristics in terms of mean seed dry weight, seeds m−2, and number of reproductive nodes, but final seed yields were similar within sowing periods. The ability of the crop to convert crop growth rate to seed number was independent of environment but decreased linearly with mean seed dry weight of the cultivar. This research suggests that pea breeders should develop new winter pea cultivars with earlier flowering to enhance yield.
Sensitivity of Chlorophyll Meters for Diagnosing Nitrogen Deficiencies of Corn in Production Agriculture
Authors: Zhang Jun , Blackmer Alfred M. , Ellsworth Jason W. , Koehler Kenneth J.
Published: May 2008

Chlorophyll meters have been widely used to diagnose N deficiencies in research trials and to help refine N fertilizer recommendations in production agriculture. The diagnoses are based on the assumption that chlorophyll meters can detect a wide range of N deficiencies under field conditions according to relationships between chlorophyll meter readings (CMRs) and yield responses to N fertilization that are established from small‐plot trials. We conducted a field‐scale study to evaluate the sensitivity of chlorophyll meters when they are used to detect N deficiencies in corn (Zea mays L.) production. The multiple year–location data were gathered in three cornfields where N fertilizer was applied at different rates in strips that crossed several soil map units. Grain yields were related to CMRs taken on corn leaves in June, July, and August of 1998–1999. Results showed that the chlorophyll meters could detect severe N deficiencies early in the season, but small and moderate deficiencies of N could not be diagnosed with reasonable certainty until it was too late to make in‐season fertilization. Two types of discontinuity are discussed in this paper as likely causes for the limited sensitivity of the chlorophyll meters. Our study suggests that problems associated with the use of chlorophyll meters to diagnose deficiencies of N in production agriculture are much greater than their use to help interpret results of well‐controlled research trials where yields are also measured.
Graphic Analysis of Genotype by Environment Interaction for Lentil Yield in Iran
Authors: Sabaghnia Naser , Dehghani Hamid , Sabaghpour Sayyed Hossain
Published: May 2008

Selection of lentil (Lens culinaris Medik) cultivars with wide adaptability across diverse farming environments is important, before recommending them to achieve a high rate of cultivar adoption. Seed yield of 11 lentil genotypes, tested in a randomized complete‐block design with four replicates across 20 environments in Iran, was analyzed using site regression (SREG) stability model. The biplot technique facilitates a visual evaluation of superior genotypes, which is useful for cultivar recommendation and megaenvironment identification. A substantial amount of genotype × environment (GE) interaction for lentil grain yield was detected. Location (L) and genotype × location (GL) variabilities were the predominant components of total yield variation. The first two principal components (PC1 and PC2) of the SREG model accounted for 76% of the total GE interaction. There were four winning genotypes and three megaenvironments according to the SREG model. The best genotype in one location was not always so in other test locations. According to the ideal‐genotype biplot, genotype G5 was better than all other genotypes; G5 exhibited both high mean yield and high stability of performance across environments. According to G + GE sources of variations, the genotypes (G4, G7, G9, and G10) were the most suitable varieties for the lentil‐producing regions in Iran.
Comparison of Corn and Soybean Yields in the United States: Historical Trends and Future Prospects
Authors: Egli D. B.
Published: May 2008

Developing successful strategies to ensure future increases in crop yield depends, in part, on a better understanding of the basis for past increases. To this end, I compared historical yield trends of two dissimilar crops—corn (Zea mays L.), a high yielding C4 grass, and soybean [Glycine max (L.) Merr.], a moderate yielding C3 legume—in high (Iowa, Illinois, Indiana) and low (Kentucky, Missouri, Tennessee) yield environments. Average state corn yield changed very little from 1866 to 1930, an era of low‐input agriculture, but it increased rapidly from 1950 to 2005 in all states as the low‐input system gave way to a high‐input system that utilized commercial hybrids, manufactured N fertilizer, herbicides, and higher plant populations. Soybean yield, first available in 1924, increased steadily from the beginning until 2005. Corn yield increased faster than soybean yield in the early decades of the high‐input era (mean growth rates of corn were 3.3 vs. 1.5% per year for soybean with a slight advantage for both crops in high yield states) in all six states, but for the rest of the era (up to 40 yr), corn and soybean yields grew at nearly the same rate (1.8% per year for corn, 1.4% per year for soybean with a slight advantage for the low‐yield states). Thus, the efforts to improve the plant (plant breeding) and production environment (better management practices) had essentially the same affect on these two very dissimilar crops.
Long‐Term Study of Properties of a Xerofluvent of the Guadalquivir River Valley under Organic Fertilization
Authors: Melero Sánchez Sebastiana , Madejón Engracia , Herencia Juan Francisco , Ruiz‐Porras Juan Carlos
Published: May 2008

The long‐term effect of inorganic and organic fertilization in a vegetable crop rotation on soil chemical and biochemical properties was investigated in a trial in southern Spain. Two crops were grown in succession, potato (Solanum tuberosumL.) and a mixed‐cropped strawberry–onion (Fragaria vescaL.–Allium cepaL.). Total organic carbon (TOC), Kjeldahl‐N, bicarbonate‐extractable P (Olsen‐P), ammonium acetate extractable‐potassium (AAE‐K), microbial biomass carbon (Cmic), and enzyme activity (dehydrogenase, β‐glucosidase, protease, and alkaline phosphatase) were determined in soils in the seventh and eighth year of management comparison. The metabolic quotient (qCO2) and the Cmic to TOC ratio were also calculated. Organically fertilized soils showed significant increases in TOC and Kjeldahl‐N, available‐P, AAE‐K, microbial biomass C, and enzymatic activities compared with those found under inorganically fertilized soils. The qCO2 values were greater in inorganic than in organic fertilized plots indicating a lower microbial community respired at a greater rate in inorganic fertilized soils. The Cmic to TOC ratio in organic plots was lower than in inorganic plots indicating that microorganism in inorganically fertilized soils could have a better efficiency in the conversion of C sources to microbial biomass. Long‐term organic fertilization positively affected soil organic matter content, thus improving soil chemical and biological fertility under arid environmental conditions in southwest Spain. However precautions must be taken as excessive accumulation of some nutrients, particularly N and P, can arise from the long‐term use of compost.
The Early History of Wheat Improvement in the Great Plains
Authors: Paulsen Gary M. , Shroyer James P.
Published: May 2008

More than 60% of U.S. wheat is grown in the Great Plains. Three classes of common wheat (Triticum aestivum L.)—hard red spring, hard red winter, and hard white—and durum (T. turgidum L. var. durum) occupy 16 million ha in the region and provide most of the U.S. grain for baked goods and pasta. This article relates the early history of the four classes and the key persons involved in their establishment. Pioneers faced many difficulties in settling the Plains, but the need for adapted cultivars was paramount. Three cultivars—‘Red Fife’ hard red spring wheat, ‘Turkey’‐type hard red winter wheat, and ‘Kubanka’ durum wheat—were the foundation for the industry. Red Fife was selected by D.A. Fife of Ontario in 1842. The cultivar spread to the northern U.S. Plains during the 1860s and dominated production for 40 yr. Turkey hard red winter wheat was introduced to Kansas by Mennonite settlers from the Ukraine, particularly B. Warkentin, in 1873 and was advanced by C.C. Georgeson, who recognized its potential. Another cultivar, ‘Kharkof’, introduced by M.A. Carleton in 1900, stimulated spread of the class throughout the Plains. Carleton also introduced Kubanka in 1900 and promoted its utilization to start the U.S. durum industry. The most recent class, hard white wheat, was initiated by E.G. Heyne and approved by the USDA in 1990. These wheats transformed American agriculture by opening a vast area for production, shifting the center of cultivation to the Plains, and changing the country into a major grain exporter.
A Century of Agronomic Education
Authors: Thien Stephen J. , Buckley Meghan E. , McFee William W.
Published: May 2008

Journals published by the American Society of Agronomy (ASA) richly chronicle the growth and success of agronomic education. To commemorate the 100th anniversary of Agronomy Journal, we compiled this historical recognition of the aggregate effort of our predecessors and colleagues. Their talented and dedicated legacy has played a significant role in feeding the world while protecting soil and water resources. By consulting our past we seek wisdom for the future, knowing that educational challenges of equal significance wait. The first volume (1909) included an article on instruction in soil physics and approximately 650 more education articles have since appeared. Most early articles focused on soils and crops course descriptions and their need for standardization. Then emphasis switched to teaching methods, aids, philosophies, student characteristics, evaluation, and curricula. Contributions from land‐grant institutions have been most numerous, but other sources are becoming more common. The number of articles has steadily increased, as has author collaboration on articles, growing from only about 10% in early years to about 70% in recent editions. We hope our abbreviated summary of the past stimulates you into consulting the writings of your esteemed predecessors and that you find validation of your efforts toward making a difference in some future agronomic record. As global pressures increase the demands on agronomic education, history may provide a pattern for success. Past achievements suggest that agronomic education is well‐founded and can be expected to impact the next century of learning as capably as it did its first century.
Winds of Change: A Century of Agroclimate Research
Authors: Steiner Jean L. , Hatfield Jerry L.
Published: May 2008

Climate has been of primary concern from the beginning of agricultural research. Early in the 20th century, climatology and agronomy evolved separately, focusing primarily on production agriculture and crop adaptation. Concepts developed include thermal units and water use efficiency. The integrated discipline of agroclimatology developed in the mid‐20th century. As theoretical understanding evolved, numerous papers related to agroclimatology were named Citation Classics. Spectral properties of plants and soils were identified that underpin today's remote sensing technologies. Commercialization of instrumentation enhanced our ability to efficiently collect data using standardized methods. Private and public‐sector partnerships advanced research capacity. Later in the 20th century, research focus shifted toward integrating knowledge into crop growth and agronomic models. Remote sensing provided capacity to gain theoretical and practical understanding of regional scale processes. In the early 21st century, recognition of earth as a system along with inter‐related human systems is driving research and political agendas. There is a pressing need to change our data‐rich to an information‐rich environment. The emerging cyberinformatics field along with natural resource and agricultural system models allow us to apply climate information to assessments and decision support related to water supply, production, environmental management, and other issues. Solutions to today's problems require interdisciplinary and multi‐sectoral teams. While needs have never been greater, fewer universities maintain critical mass required to offer advance degrees in agroclimatology. It will be increasingly important that agrclimatology attract top students and provide training and practical experience in conducting integrated systems research, communications, and team skills.
Transdisciplinary Research for a Sustainable Agriculture and Food Sector
Authors: Francis C. A. , Lieblein G. , Breland T. A. , Salomonsson L. , Geber U. , Sriskandarajah N. , Langer V.
Published: May 2008

Research in agriculture has strongly focused on discipline‐oriented, natural science‐based approaches to increasing production with success measured by short‐term, neoclassical economic evaluation. This strategy has contributed to impressive increases in food production over the last half century. Growing concerns include environmental impacts, changes in rural communities, and distribution of benefits of current agricultural systems. One major theme of this paper is a holistic, ecological, and transdisciplinary strategy for research in the agriculture and food sector, including attention to production and economics along with environmental and social factors. Agroecology provides an integrative alternative to the conventional division of research into specialized disciplines. The other primary theme is potential for a broader geographical approach to research, using the Nordic Region model as a case study for designing an educational platform to integrate research with teaching. We believe that students must develop a capacity to deal with future complexity and uncertainty, and thus be prepared to search out and answer difficult questions that have not yet been asked. In a university culture of curiosity and commitment, we need learning landscapes that prepare students to deal with change, embrace multiple dimensions of the food challenge, and establish participatory interactions with clients, communities, and organizations. In connecting scientists and consumers with the origins of their food and building awareness of the importance of the natural environment, we encourage wider support by society for research toward long‐term sustainable agriculture and food supplies. We provide a working model of how to plan regional, transdisciplinary research to sustain agriculture and food systems.
Effect of Row Spacing and Seeding Rate on Soybean Yield
Authors: De Bruin Jason L. , Pedersen Palle
Published: May 2008

Soybean [Glycine max (L.) Merr.] yield response to narrow row spacing has been consistently positive in the upper Midwest and new split‐row planters have made narrow row soybean production feasible, yet adoption has been slow in Iowa. Wide (76‐cm) and narrow (38‐cm) row spacing and four seeding rates (185,000; 309,000; 432 000; and 556,000 seeds ha−1) were evaluated at three locations during 2004, 2005, and 2006 to determine seed yield in wide and narrow row spacing and four seeding rates and evaluate economic advantages associated with changes in row spacing. Soybean planted in 38‐cm row spacing yielded 248 kg ha−1 greater than soybean planted in 76‐cm rows after adjustment for differences in final plant populations. Maximum yield at all locations was attained at a final harvest population of 462,200 plants ha−1 but >95% of the maximum yield was achieved with final populations as low as 258 600 plants ha−1. Increased production costs associated with greater seeding rates removed the yield benefit from greater harvest plant populations. Farm size of 144 ha with at least 50% of the land base dedicated to soybean production would benefit from conversion from wide to narrow rows. To break even on the investment in a split‐row planter a yield increase of 124 kg ha−1 was necessary for farms with 30% of 288 ha dedicated to soybean production. These data indicate that yield and economic benefits are sufficient to support the production of soybean in narrow rows and at seeding rates below current seeding rate recommendations.
Planting Field‐Scale Research Plots with the Aid of GPS‐Enabled Assisted Steering
Authors: Nielsen R. L. (Bob) , White Eric , Payne Jacky , Larson Norman
Published: May 2008

Field‐scale research imposes logistical challenges to planting randomized treatment plots, even for simply designed field experiments. Planter row markers offer minimal assistance when planting randomly located strips of a treatment across a field. Accurately flagging or otherwise marking treatment plots before planting to facilitate accurate planting of the same requires time and labor during a time of the year when both resources are limited. The logistical challenges associated with marking field‐scale plots are compounded with fields that are odd‐shaped or have undulating topography. We successfully used an eight‐row planter plus a tractor equipped with a commercially‐available after‐market GPS‐enabled assisted steering system to facilitate the planting of randomized treatment plots with little to no field marking required before planting. This system simplifies the logistics of planting field‐scale research trials and has proven to be acceptably accurate in pass‐to‐pass accuracies of the “guess rows” between plots.
Emergence of Polymer‐Coated Corn and Soybean Influenced by Tillage and Sowing Date
Authors: Sharratt Brenton S. , Gesch Russell W.
Published: May 2008

No tillage often delays soil warming and drying, thus sowing too early in the spring may compromise seed viability due to prolonged exposure to cold and wet soil in the northern Corn Belt. Coating seed with a temperature‐activated polymer may circumvent the adverse effects of exposing seeds to cold and wet soil. Germination and emergence of noncoated and polymer‐coated corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] seed as influenced by tillage and sowing date was examined near Morris, MN. Conventional and no tillage plots were split to accommodate early and late sowing‐date treatments while sowing‐date plots were split to accommodate seed coat treatments. Near‐surface soil water content and temperature, seed germination, and seedling emergence were monitored in 2000, 2001, and 2002. Germination of corn and soybean was delayed by as much as 6 and 11 d, respectively, as a result of sowing polymer‐coated vs. noncoated seed. This delay was also evidenced by polymer‐coated seed requiring more thermal time (>200°C h for corn and >1000°C h for soybean) to germinate and emerge than noncoated seed. Tillage, sowing date, and seed coating had little influence on plant population of corn. Sowing date and seed coating, however, influenced plant population of soybean in 2 out of 3 yr of this study. We surmise that polymer‐coated soybean seed produced a poorer stand as a result of exposure of the hypocotyl to lethal soil temperatures during emergence. This study suggests that temperature‐activated polymer coatings delay germination and emergence of corn and soybean.
Influence of Hexazinone on Pensacola Bahiagrass Growth and Crude Protein Content
Authors: Sellers Brent A. , Ferrell Jason A. , MacDonald Greg E.
Published: May 2008

Bahiagrass (Paspalum notatum Flüggé) is the most widely used introduced forage in Florida, due to its persistence and productivity on low fertility soils. Hexazinone [3‐cyclohexyl‐6‐(dimethylamino)‐1‐methyl‐1,3,5‐triazine‐2,4(1H,3H)‐dione], the only herbicide labeled for small and giant smutgrass [Sporobolus indicus (L.) R. Br. and S. indicus (L.) R. Br. var. pyramidalis (P. Beauv.) Veldkamp] control in pastures, may impact bahiagrass biomass production and crude protein (CP) content. Field experiments were conducted at two locations in 2005 and 2006 to determine the impact of hexazinone on pure stands of ‘Pensacola’ bahiagrass biomass accumulation and CP content. Hexazinone was applied at 0, 0.28, 0.56, 1.12 and 2.24 kg ai ha−1 in July of each year to actively growing bahiagrass. Hexazinone was observed to reduce bahiagrass overall biomass accumulation, but the severity of bahiagrass injury varied depending on year and location. Generally, little or no reduction in biomass accumulation occurred from hexazinone applied at 0.28 or 0.56 kg ha−1 However, hexazinone applied at the recommended use rate of 1.12 kg ha−1 resulted in 9 to 38% less dry matter accumulation relative to the untreated 84 d after treatment (DAT). At Gainesville, hexazinone did not consistently affect CP content of bahiagrass in either year. At the Ona location, CP generally increased with the application of hexazinone in both years. Crude protein was observed to increase by approximately 16 to 21% when hexazinone was applied at 1.12 kg ha−1. These data show that hexazinone application results in reduced bahiagrass production, without reducing crude protein content.
Effects of Repeated Application of Municipal Sewage Sludge on Soil Fertility, Cotton Yield, and Nitrate Leaching
Authors: Samaras Vasilios , Tsadilas Christos D. , Stamatiadis Stamatis
Published: May 2008

The effects of sludge application on soil properties and cotton (Gossypium hirsutumL.) response were investigated in an Inseptisol in central Greece. Digested sludge was incorporated in the 0 to 15 cm soil depth at rates of 10, 30, and 50 Mg ha−1, and repeated for four consecutive years. Sludge treatments were compared to an inorganic fertilizer application and an untreated control in a completely randomized design with four replications. Sludge application increased soil organic matter, associated nutrients and improved physical properties. However, soil electrical conductivity increased with increasing sludge application to levels that may affect growth of salt‐sensitive crops and warns against long‐term application that may impair essential soil functions. The multifold increase of Olsen P and nitrate N beyond crop needs is a reason of concern for surface runoff and nitrate leaching below the root zone at the higher sludge application rates. Sludge application of 10 Mg ha−1was sufficient to improve soil chemical properties with less risk of water contamination. Cotton responded to sludge application by increased nutrient uptake and yield, which indicated that sludge could replace inorganic fertilizer needs even at the lower application rate. However, fluctuations of nutrient uptake and yield between growing seasons were of greater magnitude than those caused by sludge application. Multiple regression analysis revealed that P uptake was the major limiting factor for determining cotton yield.
Interactive Effects of Carbon Dioxide and Water Stress on Potato Canopy Growth and Development
Authors: Fleisher David H. , Timlin Dennis J. , Reddy Vangimalla R.
Published: May 2008

Reductions in potato (Solanum tuberosum L.) canopy growth are observed with mild water stress. Potato growth is enhanced by elevated atmospheric carbon dioxide ([CO2]), but interactions of [CO2] and water stress on canopy formation and dry matter partitioning have not been studied. Two soil‐plant‐atmosphere research (SPAR) experiments were conducted at 370 or 740 μmol mol−1 [CO2] and six different irrigations from 10 to 100% of the daily water uptake of the control. Increases in plant length from 23 to 111 cm at 60 d after emergence (DAE), leaf appearance duration from 38 to 71 d, leaf appearance rate from 0.5 to 0.93 leaves d−1, individual leaf area from 50 to 175 cm2, and lateral branch elongation were observed as irrigation increased. Values were generally smaller for elevated [CO2] plants under water stress. Biomass increased with irrigation from 73 to 346 g plant−2. The percentage allocated to the canopy increased with irrigation from 50 to 80% in ambient and 30 to 80% in elevated [CO2]. Despite decreased canopy size, elevated [CO2] plants produced similar total biomass, but higher yield, at most irrigations. Reduced canopy mass in elevated [CO2] plants was attributed to suppressed lateral branch development due to an interactive effect of [CO2] and water stress on tuber sink strength. These results indicate that water stress predicted by climate change models will be mediated somewhat under [CO2] enrichment.
Transition from Intensive Tillage to No‐Tillage and Organic Diversified Annual Cropping Systems
Authors: Miller Perry R. , Buschena David E. , Jones Clain A. , Holmes Jeffrey A.
Published: May 2008

Transition to no‐till (NT) and organic (ORG) farming systems may enhance sustainability. Our objectives were to compare transitional crop productivity and soil nutrient status among diversified NT and ORG cropping systems in Montana. Three NT systems were designed as 4‐yr rotations, including a pulse (lentil [Lens culinarisMedik.] or pea [Pisum sativumL.]), an oilseed (canola [Brassica napusL.] or sunflower [Helianthus annuusL.]) and two cereal crops (corn [Zea maysL.], proso millet [Panicum miliaceumL.], or wheat [Triticum aestivumL.]). No‐till continuous wheat was also included. The ORG system included a green manure (pea), wheat, lentil, and barley (Hordeum vulgareL.) and received no inputs. Winter wheat in the ORG system yielded equal or greater than in the NT systems, and had superior grain quality, even though 117 kg N ha−1was applied to the NT winter wheat. After 4 yr, soil nitrate‐N and Olsen‐P were 41 and 14% lower in the ORG system, whereas potentially mineralizable N was 23% higher in the ORG system. After 4 yr, total economic net returns were equal between NT and ORG systems on a per‐ha basis. Studying simultaneous transition to diversified NT and ORG cropping systems was instructive for increased sustainability.
Characterization and Greenhouse Evaluation of Brazilian Calcined Nonapatite Phosphate Rocks for Rice
Authors: Francisco E. A. B. , Chien S. H. , Prochnow L. I. , Austin E. R. , Toledo M. C. M. , Taylor R. W.
Published: May 2008

Little information is available on the agronomic effectiveness of calcined nonapatite phosphate rock (PR) sources containing crandallite minerals in the form of Ca–Fe–Al–P for flooded and upland rice (Oryza sativa L.). We conducted laboratory and greenhouse studies to (i) characterize the mineralogical composition, (ii) investigate the solubility and dissolution behavior, and (iii) evaluate the agronomic effectiveness of two nonapatite PR sources (Juquia and Sapucaia) from Brazil and compared them with (i) a highly reactive Gafsa PR (Tunisia) containing apatite in the form of Ca–P and (ii) a reference water‐soluble triple superphosphate (TSP) for flooded and upland rice. After calcination at 500°C for 4 h, the solubility of Juquia PR and Sapucaia PR in neutral ammonium citrate (NAC) significantly increased from almost nil to a maximum of 39.3 and 114 g P kg−1, respectively. X‐ray diffraction showed that crystalline crandallite mineral was transformed to an amophorus form after calcination. The solubility behavior of the two calcined PR sources followed the same trend as Gafsa PR, that is, P release decreased with increasing equilibrium pH in the 0.01 M KCl solution (pH 3.0–8.0). At pH 3, the solubility followed: Gafsa PR > calcined Sapucaia PR > calcined Juquia PR. No P release was detected from any of the PR sources at pH ≥ 5.0 in the solution, indicating the Ca–P characteristic of the Ca–Fe–Al–P mineral controlled P dissolution of the calcined PR. Without calcination, both Juquia PR and Sapucaia PR were totally ineffective for upland rice grown on a Hiwassee clay loam (fine, kaolinitic, thermic Rhodic Kanhapludult) with pH 5.4 whereas a significant P response was observed with the calcined PR samples. For flooded rice grown on Hiwassee soil, the calcined Juquia PR and Sapucaia PR were 66 and 72%, respectively, as effective as TSP in increasing rice grain yield whereas Gafsa PR was ineffective. For upland rice grown on the unlimed soil, Gafsa PR was as effective as TSP in increasing rice grain yield whereas calcined Juquia PR and Sapucaia PR were 89 and 83% of TSP. The effectiveness of Gafsa PR was reduced to 0% after the soil was limed to pH 7.0 whereas the two calcined PR sources were reduced to 49% of TSP. Soil available P extracted by iron oxide impregnated filter paper (Pi test) or anion‐exchange resin after rice harvest correlated well with P uptake by rice grain for flooded and upland rice.
Nutrient Dynamics from Broiler Litter Applied to No‐Till Cotton in an Upland Soil
Authors: Adeli Ardeshir , Shankle Mark W. , Tewolde Haile , Sistani Karamat R. , Rowe Dennis E.
Published: May 2008

Applying broiler litter to the soil surface of a no‐till field of cotton (Gossypium hirsutumL.) increases the potential loss of its nutrients via runoff and volatilization. An experiment was conducted over 3 yr on an upland Atwood silt loam soil (fine‐silty, mixed, semiactive, thermic Typic Paleudalfs) near Pontotoc, MS, to determine the effect of broiler litter incorporation into the surface soil of no‐till cotton on nutrient availability, movement, and accumulation. The experimental design was a randomized complete block with six treatments replicated four times. Treatments were an unfertilized control, inorganic N–P–K fertilizer at the recommended rate, broiler litter at the rate of 5.2 Mg ha−1plus 34 kg ha−1supplemental N, and broiler litter at 7.8 Mg ha−1without supplemental N. A surface incorporated treatment was also included for each litter rate to test for the effects of incorporation. Broiler litter significantly increased soil nutrient concentrations compared to the control. Incorporating litter into the surface soil retained more nutrients in the soil and enhanced C sequestration over nonincorporation, indicating losses of nutrients without incorporation. Application of litter at the higher rate exceeded cotton nutrient utilization as evidenced by increasing soil NO3–N and accumulation of P, K, Cu, and Zn in the top 5 cm of the soil. Incorporating litter increased soil nutrient content higher than nonincorporation. Incorporation of litter into the surface soil of a no‐till cotton significantly reduces nutrient losses from the field.