bluuebunny/crossref_metadata_2025 huggingface dataset:
Vapor pressures and thermodynamics of oxygen-containing polycyclic aromatic hydrocarbons measured using knudsen effusion
Authors: Goldfarb Jillian L , Suuberg Eric M
Published: May 2008

Polycyclic aromatic hydrocarbons (PAHs) and their oxygenated derivatives (OPAHs) are ubiquitous environmental pollutants resulting from the incomplete combustion of coal and fossil fuels. Their vapor pressures are key thermodynamic data essential for modeling fate and transport within the environment. The present study involved nine PAHs containing oxygen heteroatoms, including aldehyde, carboxyl, and nitro groups, specifically 2-nitrofluorene, 9-fluorenecarboxylic acid, 2-fluorenecarboxaldehyde, 2-anthracenecarboxylic acid, 9-anthracenecarboxylic acid, 9-anthraldehyde, 1-nitropyrene, 1-pyrenecarboxaldehyde, and 1-bromo-2-naphthoic acid. The vapor pressures of these compounds, with molecular weights ranging from 194 to 251 g/mol, were measured using the isothermal Knudsen effusion technique in the temperature range of 329 to 421 K. The corresponding enthalpies of sublimation, calculated via the Clausius-Clapeyron equation, are compared to parent, nonoxygenated PAH compound data to determine the effect of the addition of these oxygen-containing heteroatoms. As expected, the addition of –CHO, –COOH, and –NO2 groups onto these PAHs increases the enthalpy of sublimation and decreases the vapor pressure as compared to the parent PAH; the position of substitution also plays a significant role in determining the vapor pressure of these OPAHs.
Naturally occurring progesterone in loblolly pine (Pinus taeda L.): A major steroid precursor of environmental androgens
Authors: Carson John D , Jenkins Ronald L , Wilson Elizabeth M , Howell W. Mike , Moore Ray
Published: May 2008

Progesterone, androstenedione, and androstadienedione were previously identified in the water and sediment of the Fenholloway River (Taylor County, FL, USA), a river that contains populations of masculinized female mosquitofish downstream of a paper mill, at levels higher than those in the nearby Spring Creek. Plant sterols, such as β-sitosterol in mill effluent derived from pine tree pulp, were suggested to be metabolized by bacteria to progesterone and androgens to account for the masculinization phenomenon. The current study made use of standard solid-phase methanol extraction procedures, high-performance liquid chromatography, liquid chromatography-mass spectrometry, and a cell-based, androgen-receptor transcription assay to determine naturally occurring progesterone levels in mature pine trees. Progesterone concentrations in the loblolly pine (Pinus taeda L.) were 49.34 ± 4.1 nmol/g dry mature wood (15.5 ± 1.29 μg/g), 12.26 ± 1.78 nmol/g pine needles (3.85 ± 0.56 μg/g), and 3.81 ± 0.36 nmol/g pine bark (1.19 ± 0.11 μg/g). The results suggest that naturally occurring progesterone from pine wood pulp contributes to increased progesterone levels downstream of paper mill effluent discharges and may serve as the natural steroid precursor for environmental androgen production that causes masculinization of female mosquitofish.
Mercury and other trace elements in farmed and wild salmon from british Columbia, Canada
Authors: Kelly Barry C , Ikonomou Michael G , Higgs David A , Oakes Janice , Dubetz Cory
Published: May 2008

The present study reports measured levels of Hg and other trace elements in commercial salmon feed; farmed Atlantic, coho, and chinook salmon (n = 110); and wild coho, chinook, chum, sockeye, and pink salmon (n = 91). Metal concentrations in farmed and wild salmon from British Columbia, Canada, were relatively low and below human health consumption guidelines. Methylmercury in all salmon samples (range, 0.03–0.1 μg/g wet wt) were below the 0.5 μg/g guideline set by Health Canada. Negligible differences in metal concentrations were observed between the various species of farmed and wild salmon. Metal concentrations generally were higher in commercial salmon feed compared to farmed salmon. Mercury showed slight bioaccumulation potential in farmed salmon, with biomagnification factors (BMFs) ranging between 0.8 and 1.9. Other metals, such as Cd, Pb, and Ni, exhibited biodilution, with BMFs of much less than one. The relatively low degree of biomagnification of metals observed in farmed salmon likely resulted from the combination of low gastrointestinal absorption efficiency, negligible transfer to muscle tissue relative to other compartments, and a high degree of growth dilution in these fish. Human dietary exposure calculations indicate intakes of Hg, Cd, Pb, Cu, As, and Ni via farmed and wild British Columbia salmon are a relatively small percentage of total intakes (0.05–32%) compared to other Canadian foodstuffs, such as fruits, vegetables, chicken, and beef (68–99%). Although total dietary exposure of Cd, Pb, and Cu approached provisional tolerable daily intake levels, the contribution from British Columbia salmon was less than 2%. Our findings indicate farmed and wild British Columbia salmon remain a safe source of omega-3 highly unsaturated fatty acid intake for cardioprotective and, possibly, other health benefits.
Solvent selection for pressurized liquid extraction of polymeric sorbents used in air sampling
Authors: Primbs Toby , Genualdi Susan , Simonich Staci Massey
Published: May 2008

Pressurized liquid extraction (PLE) was evaluated as a method for extracting semivolatile organic compounds (SOCs) from air sampling media, including quartz fiber filter (QFF), polyurethane foam (PUF), and a polystyrene divinyl benzene copolymer (XAD-2). Hansen solubility parameter plots were used to aid in the PLE solvent selection in order to both reduce coextraction of polyurethane and save time in evaluating solvent compatibility during the initial steps of method development. A PLE solvent composition of 75:25% hexane:acetone was chosen for PUF. The XAD-2 copolymer was not solubilized under the PLE conditions used. The average percent PLE recoveries (and percent relative standard deviations) of 63 SOCs, including polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and organochlorine, amide, triazine, thiocarbamate, and phosphorothioate pesticides, were 76.7 (6.2), 79.3 (8.1), and 93.4 (2.9)% for the QFF, PUF, and XAD-2, respectively.
Luxury Production of Leaf Chlorophyll and Mid‐Season Recovery from Nitrogen Deficiencies in Corn
Authors: Zhang Jun , Blackmer Alfred M. , Ellsworth Jason W. , Kyveryga Peter M. , Blackmer Tracy M.
Published: May 2008

Deficiencies of N during the growth of corn (Zea mays L.) are often diagnosed by using chlorophyll meters that measure chlorophyll content in leaves. The diagnoses are based on the assumption that above‐optimal supplies of N do not significantly influence chlorophyll meter readings (CMRs). The objective of this research was to assess the possibility that above‐optimal supplies of N impacted chlorophyll concentration and the effects imposed a limitation on the minimum N deficiencies that can be detected by chlorophyll meters. Our approach was to monitor temporal patterns in CMRs of nonirrigated corn that received various rates of N at various times. The results showed that the time at which N deficiency symptoms first become detectable was closely related to the amounts by which N rates fell short for maximizing grain yield. The measured symptoms of N deficiency changed with time. Temporal patterns in CMRs were affected by N treatments while yields were not greatly affected. In‐season N applications made to plants that started to show N deficiencies caused CMRs to converge with those taken on plants that always had adequate N. These observations suggest that above‐optimal supplies of N may induce a luxury production of chlorophyll that is analogous to luxury uptake of nutrients. These problems severely limit the value of using chlorophyll meters to guide in‐season fertilization in fields having near‐optimal supplies of N. The underlying problem is the uncertainty caused by difficulties associated with distinguishing luxury production of chlorophyll from symptoms of N deficiencies.
Interactive Effects of Landscape Position and Time of Application on the Response of Spring Wheat to Fall‐Banded Urea
Authors: Tiessen Kevin H. D. , Flaten Donald N. , Bullock Paul R. , Grant Cynthia A. , Karamanos Rigas E. , Burton David L. , Entz Martin H.
Published: May 2008

The objective of this experiment was to quantify the effect of landscape position and time of application on the agronomic efficiency of fall‐banded urea [CO(NH2)2] for spring wheat (Triticum aestivum L.) grown in the eastern prairie region of Canada. Landscape positions in this experiment were defined as high and low based on their relative elevations to one another within the field. Fertilizer treatments included urea banded at three different times in the fall (early, mid‐, and late fall), in the spring at planting, plus a control with no fertilizer N added. In the low landscape positions, grain yield, total crop N uptake, grain yield increases (GYI), and crop nitrogen use efficiency (NUE) for fall‐banded urea (all relative to spring‐banded urea) increased linearly with delayed application dates and declining soil temperatures on date of application. However, only crop N uptake and NUE were related to cumulative soil heat units (SHU) from date of fertilizer application until freeze‐up, and no measure of crop response to N was related to cumulative nitrification heat units (NHU). In the high landscape positions, the performance of fall‐banded urea was not related to any measures of time and/or soil temperature. These results can be used to predict the increase in crop response to fall‐banded N as a result of delaying application in low areas of the landscape. Our study also shows that date of application and soil temperature are robust and practical indicators for determining the appropriate time to fall‐band urea fertilizer in these areas.
Application of Spectral Remote Sensing for Agronomic Decisions
Authors: Hatfield J. L. , Gitelson A. A. , Schepers J. S. , Walthall C. L.
Published: May 2008

Remote sensing has provided valuable insights into agronomic management over the past 40 yr. The contributions of individuals to remote sensing methods have lead to understanding of how leaf reflectance and leaf emittance changes in response to leaf thickness, species, canopy shape, leaf age, nutrient status, and water status. Leaf chlorophyll and the preferential absorption at different wavelengths provides the basis for utilizing reflectance with either broad‐band radiometers typical of current satellite platforms or hyperspectral sensors that measure reflectance at narrow wavebands. Understanding of leaf reflectance has lead to various vegetative indices for crop canopies to quantify various agronomic parameters, e.g., leaf area, crop cover, biomass, crop type, nutrient status, and yield. Emittance from crop canopies is a measure of leaf temperature and infrared thermometers have fostered crop stress indices currently used to quantify water requirements. These tools are being developed as we learn how to use the information provided in reflectance and emittance measurements with a range of sensors. Remote sensing continues to evolve as a valuable agronomic tool that provides information to scientists, consultants, and producers about the status of their crops. This area is still relatively new compared with other agronomic fields; however, the information content is providing valuable insights into improved management decisions. This article details the current status of our understanding of how reflectance and emittance have been used to quantitatively assess agronomic parameters and some of the challenges facing future generations of scientists seeking to further advance remote sensing for agronomic applications.
Beachell and Borlaug: Two Giants of the American Society of Agronomy's First Century
Authors: Milford Murray H. , Runge E. C. A.
Published: May 2008

On the occasion of the 100th anniversary of the American Society of Agronomy, it is appropriate that recognition be given to two men: Henry M. Beachell, internationally recognized and most long‐lived 73‐yr member, until his death in December 2006; and to Norman E. Borlaug, who without doubt, is the most widely acclaimed of the Society's members. Both men had scientific accomplishments that were crucial to the Green Revolutions associated with the production of rice (Oryza sativa L.) (Beachell) and wheat (Triticum aestivum L.) (Borlaug). Their professional careers have much in common and their interactions with each other had significant impact on the careers of both. The purposes of this paper are to gain insight into their thinking and to highlight the accomplishments that make them the most well‐known agronomists of the Society's first 100 yr.
No‐Tillage Crop Production: A Revolution in Agriculture!
Authors: Triplett G. B. , Dick Warren A.
Published: May 2008

For thousands of years, agriculture and tillage were considered synonymous. It was simply not thought possible to grow crops without first tilling the soil before planting and for weed control. The advent of modern herbicides permitted no‐tillage (NT) to be developed and practiced on actual working family farms. No‐tillage is generally defined as planting crops in unprepared soil with at least 30% mulch cover. Adoption of NT after its successful demonstration in the 1950s was slow. However, with better planters, herbicides, and accumulated experience, NT began to be widely adopted in the 1980s in the United States and then in Australia, South America, and Canada. Today, approximately 23% of the total cropland in the United States is planted using NT. No‐tillage has revolutionized agricultural systems because it allows individual producers to manage greater amounts of land with reduced energy, labor, and machinery inputs. At the same time, NT is a very effective erosion control measure and improves water and fertilizer use efficiency so that many crops yield better under NT than under tilled systems. Tillage, like crops, can be rotated but the benefits of NT are most likely to be realized with continuous application. We review some of the early work that led to the development of NT and how NT impacts the crop, soil, hydrology, and farm economics. While highly sustainable, there are still many challenges that remain for researchers to solve so the benefits of NT can be realized on expanded land area and for more crops, worldwide.
After 10,000 Years of Agriculture, Whither Agronomy?
Authors: Miller Fred P.
Published: May 2008

The evolution of agriculture within the last 11,000 yr marked the first major inflection point in food yield and changed forever the character of the human condition. The application of technology to agriculture early in the 20th Century induced the next major crop yield inflexion point. Identifying the technological wellspring from which increased rates of productivity will be obtained in the decades ahead is far less obvious than during the last century. The agronomic challenge for the decades to come is to increase productivity per unit of land enough to preclude appropriation of other ecosystems for cropland expansions while simultaneously increasing the efficiency of production inputs, reducing their leakage to the environment, and sustaining the integrity of those ecological processes that undergird these intense biological production systems. Such a goal will require different metrics to measure agricultural sustainability and garner public support, new funding sources, and more holistic institutional arrangements. Agronomists, while playing a major role in meeting this challenge, will not necessarily dominate the agenda.
Then and Now: 125 Years of Dryland Wheat Farming in the Inland Pacific Northwest
Authors: Schillinger William F. , Papendick Robert I.
Published: May 2008

This article is a history of dryland wheat (Triticum aestivum L.) farming in the low‐precipitation (<300 mm annual) region on the Columbia Plateau of the Inland Pacific Northwest (PNW) of the United States. Numerous technological advances, environmental problems, and sociological factors influenced wheat farming since its inception in 1880. The wheat‐based economy traces back to the pioneers who faced many challenges that included scarcity of water and wood, unprecedented wind erosion, drought, and minimal equipment. Throughout the years, major technological breakthroughs include: (i) horse (Equus caballus) farming to crude crawler tractors to the 350+ horse power tractors of today, (ii) transition from sacked grain to bulk grain handling, (iii) nitrogen fertilizer and herbicides, (iv) the rotary rodweeder, and (v) the deep furrow split‐packer drill to allow early planting of winter wheat into stored soil water. Cultural practices have evolved from repeated passes with high‐soil‐disturbance tillage implements to today's conservation tillage management. The 2‐yr winter wheat–summer fallow rotation continues as the dominant cropping system as it is less risky and more profitable than alternative systems tested so far. Improved wheat cultivars for deep furrow planting continue to be developed with good emergence, disease resistance, winter hardiness, grain quality, and other values. In the past 125 yr, average farm size has grown from 65 to 1400 ha and wheat grain yield increased from <1.0 to 3.4 Mg ha−1. Since the 1930s, government farm programs have provided unwavering support that, in the last several decades, accounts for about 40% of gross farm income.
Harvest Techniques Change Annual Warm‐Season Legume Forage Yield and Nutritive Value
Authors: Muir James P. , Butler Twain J. , Wolfe Richard M. , Bow John R.
Published: May 2008

Comparison among warm‐season legume forage trials may not be valid if harvest techniques vary. To address this question, herbage dry matter (DM) yields, branching, crude protein (CP), and fiber concentrations for nine warm‐season annual herbaceous legumes were measured by hand‐plucking all leaves and pliable tips or clipping at 7.5‐ or 15‐cm height. The experiment was conducted in Texas on a Windthorst fine sandy loam over 2 yr. Harvest technique did not affect DM yield in 2004, but the hand‐plucked harvest technique produced 34 to 39% less forage in 2005 (low rainfall year) compared with the clipped plots. Most entries had greater branching on hand‐plucked than on clipped plants (entry by harvest P < 0.05). Crude protein concentration was greater (P < 0.05) and fiber concentrations lower in the hand‐plucked compared with the clipped plants. These results suggest that neither yields nor nutritive values of hand‐plucked forage trials examining annual warm‐season herbaceous legumes should be compared with clipped forage trials, whereas clipping heights may be less problematic. Results support a careful choice of experiment harvest technique based on the future field‐scale harvest method or degree of target herbivore selectivity.
Do Synergistic Relationships between Nitrogen and Water Influence the Ability of Corn to Use Nitrogen Derived from Fertilizer and Soil?
Authors: Kim Ki‐In , Clay D. E. , Carlson C. G. , Clay S. A. , Trooien T.
Published: May 2008

To improve site‐specific N recommendations a more complete understanding of the mechanisms responsible for synergistic relationships between N and water is needed. The objective of this research was to determine the influence of soil water regime on the ability of corn (Zea mays L.) to use N derived from fertilizer and soil. A randomized split‐block experiment was conducted in 2002, 2003, and 2004. Soil at the site was a Brandt silty clay loam (fine‐silty, mixed, superactive frigid Calcic Hapludoll). Blocks were split into moderate (natural rainfall) and high (natural + supplemental irrigation) water regimes. Nitrogen rates were 0, 56, 112, and 168 kg urea‐N ha−1 that was surface applied. Water, soil N, and N fertilizer use efficiencies were determined. Plant utilization of soil N was determined by mass balance in the unfertilized control plots and by using the δ15N approach in fertilized plots. Findings showed that: (i) plants responded to N and water simultaneously; (ii) N fertilizer increased water use efficiency (170 kg vs. 223 kg grain cm−1 in 0 and 112 kg N ha−1 treatments, respectively); and (iii) water increased the ability of corn to use N derived from soil (67.7 and 61.6% efficient in high and moderate water regimes, respectively, P = 0.002) and fertilizer (48 and 44% efficient in high and moderate water regimes, respectively, P = 0.10). Higher N use efficiency in the high water regime was attributed to two interrelated factors. First, total growth and evapotranspiration (ET) were higher in the high than the moderate water regime. Second, N transport to the root increased with water transpired. For precision farming, results indicate that: (i) the amount of N fertilizer needed to produce a kg of grain is related to the yield loss due to water stress; and (ii) the rate constant used in yield goal equations can be replaced with a variable.
A Century of Women in Agronomy: Lessons from Diverse Life Stories
Authors: McIntosh Marla S. , Simmons Steve R.
Published: May 2008

The experiences, achievements, wisdom, and philosophies of eight exemplary women agronomic scientists are told to provide insights into the history, diversity, and evolution of the agronomic sciences. The stories of these women, whose lives and careers span the last century (born 1889 to 1973), integrate their personal and professional lives to create a multidimensional understanding of the past to help us see a clearer vision for the future. Each woman's story contributes a unique and significant perspective on the roles of individuals in the agronomic sciences. The compilation of these life stories reveals important similarities shared among women. Their lives and words are meant to inspire others as they reflect on their own personal and professional goals and approaches to attaining them. This paper can be a resource for teachers seeking to stimulate student discussion about the role of gender within the agronomic profession, as well as about professional ethics and cultural diversity. While intending to be thought‐provoking, the authors sought to reveal the importance of women in the continuing evolution of agronomy and to affirm the value of human diversity in a constantly changing world.
Evaluation of Soil Environment after Saline Soil Reclamation of Xinjiang Oasis, China
Authors: Hua Fan , Xudong Pan , Yuyi Li , Fu Chen , Fenghua Zhang
Published: May 2008

Land degradation resulting from soil salinity is a primary problem in arid farmland. This study clarifies the characteristics and regulation of reclaimed salinized farmlnd in a desert oasis. As a case study, we examined an alluvial fan oasis in the Manas River Valley using fixed position experiments, spacial substitutes, and a trend estimation model derived from principal component analysis. In this way, we analyzed the succession of plant and soil characteristics on farmland at the bottom of alluvial fan oasis. With increasing time following reclamation, perennial haloduric plants were replaced by annual plants. The area then entered a stable stage from 6 to 8 yr following reclamation. The total salt decreased gradually and then increased, while soil nutrients showed the opposite trend. The trend estimation model derived from principal components analysis revealed that the general soil quality improved over the first 10 yr before declining thereafter. By systematically analyzing the various indices of soil quantity, an early warning of changes in soil quality can be provided 10 to 15 yr in advance.
Statistical Analysis of Field Trials with Changing Treatment Variance
Authors: Lee Curtis J. , O'Donnell Maryann , O'Neill Mick
Published: May 2008

This is a discussion paper that presents no new material but challenges the way that field trials with changing treatment variances have been traditionally analyzed. We argue that one should always expect the variance of yield to change when the yields are obtained from plots with different plant densities. To illustrate, a turnip (Brassica rapa L.) sowing density by sowing date experiment is analyzed using analysis of variance and residual maximum likelihood methods. Deviance is used to compare the statistical models and demonstrate that residual maximum likelihood provides a better analysis when a linear mixed model is fitted to account for a changing variance due to sowing density. The analysis is further improved when sowing date, which also has a changing variance, is incorporated into the model. Plant density trials should always be assumed to have changing variance. Linear mixed models (with a residual maximum likelihood algorithm for estimating variance parameters) can be used to obtain superior analyses and make better research decisions.
Soybean Seed Yield Response to Planting Date and Seeding Rate in the Upper Midwest
Authors: De Bruin Jason L. , Pedersen Palle
Published: May 2008

Planting date and seeding rate are agronomic decisions that producers can use to maximize soybean [Glycine max (L) Merr.] seed yield and economic return. Current information on the response to planting date and seeding rate may underestimate the yield penalty for delayed planting in northern climates and overestimate the seeding rate required to optimize yield. The objective was to determine the effect of planting date and seeding rate on soybean seed yield at environments with different yield potentials in Iowa. Field experiments were conducted in six locations between 2003 and 2006 for a total of 13 environments. Four seeding rates were planted at four dates between late April and the middle of June. No yield difference existed between the late April and early May planting dates and the yield decline rate between each date was consistent among the six locations. Harvest plant populations were not influenced by planting date indicating that plant establishment does not pose a limitation to late April planting. Harvest plant populations required to reach 95% of the maximum yield were as great as 290,800 or as low as 194,000 plants ha−1, for locations seeded in 38‐cm row spacing and 157,300 to 211,800 plants ha−1 for locations seeded in 76‐cm row spacing. Planting in late April or early May increased economic return ha−1 but there was no difference between seeding rates of 185,300 and 556,000 seeds ha−1, accounting for additional seed costs. In the cool spring climate of the upper Midwest soybean producers can increase yield by planting soybean 1 to 2 wk earlier than current planting dates. These data also suggest that the optimal seeding rate for most locations is less than current seeding rates.
No‐Till and Conventional‐Till Cotton Response to Broiler Litter Fertilization in an Upland Soil: Lint Yield
Authors: Tewolde H. , Shankle M. W. , Sistani K. R. , Adeli A. , Rowe D. E.
Published: May 2008

The effectiveness of poultry litter as cotton (Gossypium hirsutum L.) fertilizer is not well documented for upland soils in the southern and southeastern United States. The objective of this research was to measure cotton yield response to broiler litter fertilization in contrast to inorganic N fertilization and to quantify yield reduction due to lack of incorporation under no‐till and conventional‐till systems in an upland soil. Six treatments were tested in two unreplicated adjacent fields, one under no‐till (NT) and the other under conventional‐till (CT) management, from 2003 to 2006 near Pontotoc, MS. The treatments consisted of an unfertilized control (UTC), a standard fertilization (STD) with urea‐ammonium nitrate solution (UAN), fertilization with ∼5.2 Mg ha−1 incorporated or unincorporated broiler litter to supply 67% of the N need plus 34 kg ha−1 UAN‐N to supply 33% of the N need, and fertilization with ∼7.8 Mg ha−1 incorporated or unincorporated broiler litter. Lint yield results showed broiler litter was a more effective cotton fertilizer than inorganic fertilizers under both NT and CT systems. The UTC produced an average across years of 870 kg ha−1 lint under NT and 1105 kg ha−1 under CT. The STD treatment increased yield over the UTC by only 121 kg ha−1 (14%) under the NT and did not affect yield under the CT. Fertilization with litter‐only when incorporated, relative to the UTC, increased lint yield by 260 kg ha−1 (30%) under NT and by 137 kg ha−1 (12%) under CT. The yield of this incorporated litter‐only treatment exceeded the yield of the STD treatment by 139 kg ha−1 (14%) under NT and by 115 kg ha−1 (10%) under CT. Fertilization with litter also resulted in greater leaf area index but less chlorophyll index than the STD treatment. Lack of litter incorporation reduced yield by up to 84 kg ha−1 under NT but did not affect yield under CT. Overall, broiler litter appears to be a more effective cotton fertilizer than conventional inorganic N fertilizers for this upland soil, but the inherent inability to incorporate under no‐till may reduce this benefit.
Arbuscular Mycorrhizal Colonization Response to Three Seed‐Applied Fungicides
Authors: Murillo-Williams Adriana , Pedersen Palle
Published: May 2008

In soybean [Glycine max (L.) Merr.], arbuscular mycorrhizae (AM) enhance nutrient and water status and may increase root resistance to soilborne pathogens. However, the fungicides that are routinely applied to the seed may reduce AM colonization, reducing these benefits. Thus, the objective of this research was to assess the effect of three commonly used seed‐applied fungicides on AM colonization of soybean in Iowa. Soybean seeds were treated with the fungicides mefenoxam, fludioxonil, mefenoxam + fludioxonil, and a nontreated control. Soil fumigation with a mixture of 1,3‐dichloropropene and chloropicrin was used as a tool to measure any direct effect of the fungicide on plant growth or yield parameters. There was a significant fumigation by seed treatment interaction in 2005. Seed‐applied fungicides that contained fludioxonil favored AM colonization in nonfumigated soil, where fludioxonil‐treated plants had double the root colonization of the control (6 vs. 2.8%, respectively) and five times more root colonization than plants treated with mefenoxam (6 vs. 1.1%, respectively). In the fumigated soil, plants treated with mefenoxam alone or in combination with fludioxonil had lower colonization than the control and fludioxonil‐treated plants. Fumigation did not significantly reduce or increase mycorrhizal colonization across locations. No differences in grain yield, final stand, or grain composition were found among seed‐applied fungicides or between nonfumigated and fumigated soil. With the exception of mefenoxam in fumigated soil in 2005, there was no evidence of a reduction in mycorrhizal colonization of soybean roots with seed‐applied fungicides under field conditions.
Simulating Leaf Appearance in Rice
Authors: Streck Nereu Augusto , Bosco Leosane Cristina , Lago Isabel
Published: May 2008

Most rice (Oryza sativa L.) simulation models assume that only temperature affects leaf appearance rate (LAR). This assumption ignores results from controlled environment studies that show that LAR in rice is not constant with time (calendar days) under constant temperature. The Streck model, which takes into account age effects on LAR, improved the prediction of leaf appearance in winter wheat (Triticum aestivum L.) cultivars compared with the Wang and Engel (WE) model and the phyllochron model but has not been evaluated in rice. The objective of this study was to adapt and evaluate the Streck model to simulate main stem LAR and leaf number in rice. A 4‐yr experiment with several sowing dates from 2003–2004 to 2006–2007 was performed at Santa Maria, RS, Brazil. Seven rice cultivars were used: IRGA 421, IRGA 420, IRGA 417, IRGA 416, BRS 7 (TAIM), BR‐IRGA 409, and EPAGRI 109. Plants were grown in 12‐L pots during the 4 yr, and in a paddy rice field during the 2006–2007 growing season. Coefficients necessary to run the Streck model, the WE model, and the phyllochron model were estimated with data from five sowing dates of the 2003–2004 growing season and the models were evaluated with independent data from the other three growing seasons. Predictions of the main stem leaf number, represented by the Haun Stage (HS), were better with the Streck model. The RMSE was 0.7, 1.0, and 1.8 leaves, for the Streck model, the WE model, and the phyllochron model, respectively.
Postanthesis Moderate Wetting Drying Improves Both Quality and Quantity of Rice Yield
Authors: Zhang Hao , Zhang Shenfeng , Yang Jianchang , Zhang Jianhua , Wang Zhiqin
Published: May 2008

A major challenge in rice (Oryza sativa L.) production in China is to cope with a declining availability of fresh water without compromising grain yield and grain quality. This study was designed to determine if alternate wetting and moderate soil drying during grain filling could maintain grain yield and grain quality. Two rice cultivars, Zhendao 88 (japonica) and Shanyou 63 (indica), were field‐grown at Yangzhou, China. Three irrigation treatments, alternate wetting and moderate soil drying (WMD, rewatered when soil water potential reached −25 kPa at 15–20 cm depth), alternate wetting and severe soil drying (WSD, rewatered when soil water potential reached −50 kPa), and conventional irrigation (CI, continuously flooded), were conducted from 6 d after heading to harvestable maturity. Root oxidation activity, the photosynthetic rate of the flag leaf, and activities of key enzymes in sucrose‐to‐starch conversion in grains during the late grain‐filling stage were significantly increased under WMD, whereas they were significantly reduced under WSD. The grain yield was increased by 9.3 to 9.5% under WMD, while it was reduced by 7.5 to 7.8% under WSD, when compared with that under CI. Water applied to WMD was 44% and to WSD was 25% of the amount applied to CI. The WMD significantly improved milling, appearance, and cooking qualities, while WSD decreased these qualities. We conclude that a moderate wetting drying regime during the grain‐filling phase of rice holds great promise to both increase yield quantity and quality and also could save precious fresh water resources.
Interspecies Variation of Forage Nutritive Value and Nonstructural Carbohydrates in Perennial Cool‐Season Grasses
Authors: Zhao Duli , MacKown Charles T. , Starks Patrick J. , Kindiger Bryan K.
Published: May 2008

Knowledge of grass genotypes nonstructural carbohydrate (NSC) variation is one component to be considered when developing a successful forage and livestock management program. The objective of this study was to determine variations in concentrations of NSC, crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) among perennial cool‐season grasses grown in the southern Great Plains at the preheading stage. Grasses evaluated included four tall fescue (Festuca arundinacea L.), two Festulolium (Lolium. multiflorum Lam. × Festuca arundinaceae), one tall wheatgrass [Thinopyrum ponticum (Podp.) Z.‐W. Liu & R.‐C. Wang], two intermediate wheatgrasses [T. intermedium (Host) Barkworth & D.R. Dewey], and four smooth bromegrasses (Bromus inermis Leyss). Grass species influenced forage concentrations of NSC, CP, NDF, and ADF. Averaged across years, concentrations of forage total NSC, CP, NDF, and ADF ranged from 70 to 112, 81 to 138, 548 to 614, and 288 to 321 g kg−1 dry weight (DW), respectively, among the 13 entries. Differences in the relative contribution of each NSC component to total NSC were small among the five species. Averaged across the entries, glucose, fructose, sucrose, fructans, and starch accounted for 14, 10, 15, 38, and 23% of total NSC, respectively. Producers seeking to improve the provision of energy to livestock would be served best by using smooth bromegrass with superior NSC concentration rather than by a tall fescue entry with low NSC concentration.
Canopy Nitrogen Reserves: Impact on Soybean Yield and Seed Quality Traits in Northern Latitudes
Authors: Naeve Seth L. , O'Neill Tracy A. , Miller-Garvin Jill E.
Published: May 2008

Soybean [Glycine max (L.) Merr.] seed produced in the upper Midwest of the United States is lower in protein concentration than soybean produced throughout much of the Corn Belt, the southern United States, and Brazil. As protein comprises on average more than 400 g kg−1 of the soybean seed, yields in northern latitudes may be limited by seed protein accrual. Our objective was to examine the role of canopy N reserves at maximum vegetative growth (R5.5) on seed yield, and seed protein, oil, and sulfur concentrations in the upper Midwest. Six commercial cultivars with similar yield potentials and maturities were grown in 10 central Minnesota environments. Mean cultivar seed yields ranged from 3.1 to 3.2 Mg ha−1, while mean environment yields ranged from 1.7 to 5.0 Mg ha−1. High‐yielding environments produced soybean plants with greater R5.5 canopy N reserves and total dry matter (DM) and seed with low protein and S concentration. Mean R5.5 canopy N quantities ranged from 117 to 309 kg ha−1. These quantities were sufficient to satisfy seed N requirements which ranged from 43 to 91 kg ha−1. While R5.5 canopy N and DM may have a positive influence on seed yields in these upper Midwestern environments, seed protein concentration effects appear to be mediated through effects on seed yield. A positive correlation between yield and seed N to S ratio noted here indicates that sulfur may be more limited than protein at high yield levels. Oil concentration was not affected by yield.
Do Cultivar and Burning Affect Forage Yield and Incidence of Verticillium Wilt or Insect Pests in Alfalfa Stands?
Authors: Acharya S. N. , Huang H. C. , Cárcamo H. A. , Basu S. K. , Entz T. , Erickson S. , Friebel D.
Published: May 2008

Alfalfa (Medicago sativa L.) is one of the most important forage crops in Canada and many parts of the world. Two experiments were conducted over a 13‐yr period (1989–2002) in Lethbridge, Alberta, Canada with five alfalfa cultivars. In the first experiment, ‘Barrier’ and ‘Pacer’ were given three burn treatments (no burn, burn every year, and burn in alternate years) while in the second experiment four cultivars ‘Barrier’, ‘Heinrichs’, ‘Trumpetor’, and ‘Legend’ were given burn or no burn treatments to determine the impact of burning of crop residues on forage yield, incidence of verticillium wilt, and insect pest abundance. Burning did not affect forage yield or incidence of verticillium wilt of alfalfa. Barrier had the highest yield and lowest disease incidence. Burning had a significant albeit variable impact on abundance of alfalfa plant bugs, lygus bugs, aphids, and leafhoppers but not on abundance of alfalfa weevil. The lack of effectiveness of the burning treatments on forage yield and adverse environmental consequences of burning such as air pollution, hazardous loss of visibility during burning operations, and loss of crop cover suggest that burning should not be used as a production strategy for this widely grown crop.
Upland Switchgrass Yield, Nutritive Value, and Soil Carbon Changes Under Grazing and Clipping
Authors: Sanderson Matt A.
Published: May 2008

There have been few evaluations of switchgrass (Panicum virgatum L.) cultivars under multiple harvest managements in the northeastern United States. The objective of this study was to determine the yield, nutritive value, and soil C changes of switchgrass cultivars under grazing and clipping. In 1999, ‘Cave‐in‐Rock’, ‘Trailblazer’, and ‘Shawnee’ switchgrass were established in field plots at Rock Springs, PA, and in pastures in southeastern Pennsylvania. In 2000 and 2001, two‐ and three‐cut treatments were imposed at Rock Springs. At the southeastern Pennsylvania site, pastures were grazed three or four times per year during 2000 to 2004. Forage yield, crude protein (CP), neutral detergent fiber (NDF), and neutral detergent fiber digestibility (NDFD) were determined at each harvest. Soil was analyzed for C and stable C isotopes before planting in 1999 and at the end of the experiments. Cultivars differed slightly in yield and nutritive value. Variation in forage yield was greater among years and management treatments (3300 to 8200 kg ha−1) than among cultivars (5900 to 9400 kg ha−1). Trailblazer suffered from leaf diseases and lodging during wet years. There were no differences among cultivars in soil C. Soil C accumulated in the surface 5 cm of soil after 7 yr at Rock Springs, but soil C did not change after 5 yr of grazing. By the end of the experiments, about 20% of soil C in the surface 5 cm was derived from switchgrass. Cave‐in‐Rock and Shawnee are equally suited and superior to Trailblazer for hay and grazing in Pennsylvania and similar areas in the northeast.
On‐Farm Evaluation of the Improved Soil Nmin–based Nitrogen Management for Summer Maize in North China Plain
Authors: Cui Zhenling , Chen Xinping , Miao Yuxin , Zhang Fusuo , Sun Qinping , Schroder Jackie , Zhang Hailin , Li Junliang , Shi Liwei , Xu Jiufei , Ye Youliang , Liu Chunsheng , Yang Zhiping , Zhang Qiang , Huang Shaomin , Bao Dejun
Published: May 2008

The improved soil Nmin–based N management is a promising approach to precision N management, which determines the optimum side‐dress N rates based on N target values and measured soil nitrate N content in the root soil layer at different growth stages. A total of 148 on‐farm N‐response experiments, in seven key summer maize (Zea mays L.) production regions of North China Plain (NCP) from 2003 to 2005, were conducted to evaluate the Nmin–based N management compared to traditional farmer's N practices. The recommended N rates based on the improved soil Nmin method were not significantly different ( ≤31 kg N ha−1) from those determined by yield response curves (n = 13). The average N rate determined with the soil Nmin method (157 kg N ha−1) was significantly lower than farmer's practice (263 kg N ha−1), while maize grain yield was 0.4 Mg ha−1 higher than farmer's N practice (8.5 Mg ha−1) across all sites (n = 148). As a result, the improved soil Nmin–based N management significantly increased net economic gains by $202 ha−1, reduced residual nitrate N content and N losses by 44 kg N ha−1 and 65 kg N ha−1, respectively, and improved recovery N efficiency, agronomic N efficiency and N partial factor productivity by 16%, 6 kg kg−1 and 36 kg kg−1, respectively, compared with farmer's N practice. We conclude that the improved soil Nmin–based N management can be applied for summer maize production in NCP for improved N use efficiency and reduced environmental contamination.
Impact of Defoliation on Corn Forage Quality
Authors: Roth G. W. , Lauer J. G.
Published: May 2008

Hail damage can be a serious problem on corn (Zea mays L.) grown for silage. The value of corn grown for silage is a function of both the yield and quality of the forage produced. An improved understanding of the effects of defoliation on forage quality would improve the ability of agronomists, farmers, and crop insurance adjusters to assess the economic impact of hail damage to corn harvested for forage. The objective of this study was to evaluate the effects of defoliation on the forage quality corn grown for silage production. Experiments were conducted during 2000, 2001, and 2002 at Arlington and Marshfield, WI, and State College, PA. Corn quality measures responded similarly to defoliation treatments across most environments. Increasing defoliation either did not affect quality, especially at V7 and V10 stages, or lowered quality, especially at the R1 and R4 stages of development. The largest differences in neutral detergent fiber (NDF), acid detergent fiber (ADF), and in vitro true digestibility occurred at R1 and R4. Starch content was most affected when defoliation occurred at R1. The response of NDF digestibility was inconsistent across environments. These changes in forage quality resulted in decreases in Milk Mg−1 and Milk ha−1 with increasing defoliation in most environments. Predictive models for estimating forage quality and yield losses can be used to improve estimates of the impact of defoliation caused by hail on corn grown for silage.
Responses of Upland NERICA Rice to Nitrogen and Phosphorus in Forest Agroecosystems
Authors: Oikeh S. O. , Nwilene F. , Diatta S. , Osiname O. , Touré A. , Okeleye K. A.
Published: May 2008

New Rice for Africa (NERICA) cultivars are widely adopted interspecific crosses between Oryza sativa and O. glaberrima but their responses to fertilizer was not known. In 2004 and 2005, four released NERICAs (NERICA 1, 2, 3, 6) under two levels of phosphorus (0 and 2.6 g m−2) and four of nitrogen (0, 3, 6, and 12 g m−2) were evaluated on an acid Typic Haplustult at Ikenne (6°54′ N, 3°42′ E) in the Nigerian forest agroecosystem. In 2004, averaged over N levels, NERICA 3 attained physiological maturity most quickly (92 days after seeding [DAS]) at 2.6 g P m−2. But under drought stress (2005), although NERICA 3 was the first to initiate panicles (49 DAS) and to reach midflowering (73 DAS), maturity was delayed until 100 to 101 DAS with or without P. Also, in 2005, NERICA 6 took a much longer time to mature (110–111 DAS) than the other cultivars. Therefore, NERICAs 3 and 6 were the least suitable cultivars for low‐input, drought‐prone environments. At low N of 3 g m−2 and zero P, paddy yield was highest in NERICA 1. With application of 12 g N m−2, NERICA 1 also yielded 20 to 41% more than the others, implying that it had a potential for tolerance to low N and was the most N‐responsive among the cultivars evaluated under limited P. Moderate levels of N (6 g m−2) and P (2.6 g m−2) are recommended for NERICAs in smallholder low‐input production systems.
Estimating Plant‐Available Water Using the Simple Inverse Yield Model for Claypan Landscapes
Authors: Jiang Pingping , Kitchen Newell R. , Anderson Stephen H. , Sadler E. John , Sudduth Kenneth A.
Published: May 2008

Plant‐available water (PAW) is one of the fundamental soil factors affecting crop yield, yet quantitative determination of plant‐available water capacity (PAWc) at a field scale has been challenging. A simple inverse yield model (SIYM) has been devised and shown to be successful in estimating PAWc at a field scale for well‐drained soils by matching simulated corn (Zea mays L.) yield with measured yield. For other soils, however, SIYM is yet to be tested. Our objective was to evaluate SIYM performance in estimating PAWc for poorly‐drained claypan‐soil landscapes. Soil PAWc to a depth of 1.2 m (PAW1.2) was measured at 19 and 18 sampling locations for two claypan‐soil fields, Fields 1 and 2, respectively. Corn yield maps of the two fields (nine site‐years between 1993 and 2003) were used with the model to estimate PAWc Yield reduction associated with low precipitation and high vapor‐pressure deficit during corn reproductive stages, and large yield variation in dry years were indications available water was the main yield‐limiting factor. The regression r2 values between SIYM‐estimated PAWc and the measured PAW1.2 were 0.43 for Field 1 and 0.31 for Field 2 with estimating errors of 18 and 50 mm, respectively. In Field 2, SIYM estimated markedly lower PAWc compared with the PAW1.2 at the most‐eroded backslope areas, where claypan characteristics were most prevalent. The SIYM‐PAWc estimates would be more informative in assessing soil productivity because they are based on crop‐water relations and not solely on soil texture.