bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation of ovarian steroidogenesis in vitro by gonadotropin in common carp Cyprinus carpio: interaction between calcium- and adenylate cyclase-dependent pathways and involvement of ERK signaling cascade
Authors: Paul Sudipta , Kundu Sourav , Pramanick Kousik , Bandyopadhyay Arun , Mukherjee Dilip
Published: July 2010

Multiple signal transduction pathways mediating gonadotropin-induced testosterone and 17β-estradiol (E2) production were identified in carp ovarian theca and granulosa cells in short-term co-incubation. Inhibitors of voltage-sensitive calcium channels (VSCCs) and calmodulin attenuated human chorionic gonadotropin (HCG)-induced steroid production, whereas modulators of adenylate cyclase and protein kinase A (PKA) increased their production, indicating that both calcium- and PKA-dependent pathways are involved in the regulation of gonadotropin-induced steroidogenesis in carp ovary. Interactions between these two pathways are evident from the positive effect of elevated intracellular calcium on HCG-induced steroid production and the reduction of forskolin (FK)- and dibutyryl cAMP (dbcAMP)-induced steroidogenesis by inhibitors of VSCCs and calmodulin. In this study, we found the involvement of a third signaling pathway, a mitogen-activated protein kinase (MAP kinase), in the regulation of gonadal steroidogenesis in this fish. An antagonist of mitogen-activated protein kinase kinases 1/2 (MEK1/2; also known as MAP2K1/MAP2K2) markedly attenuated HCG-induced steroid production. Cells treated with HCG stimulated MEK1/2-dependent phosphorylation of extracellular signal-regulated protein kinases 1/2 (ERKs1/2) in a concentration and time-dependent manner. Moreover, ERK1/2 activation in cells was mimicked by FK and dbcAMP suggesting that ERK1/2 transduce signal downstream of PKA in HCG-induced ovarian steroidogenesis. Evidence for presence of cross talk between calcium-dependent pathways and this MAP kinase cascade has been shown by demonstrating the inhibitory effects of verapamil and calmodulin on ERK1/2 activation after HCG stimulation. Our results suggest that activation of ERK1/2 by HCG as well as other agents may be a key mechanism for the modulation of gonadotropin-induced steroidogenesis in carp ovary.
The dielectric response of compacted cementitious composites
Authors: Panzera T.H. , Borges P.H.R. , Rubio J.C. , Bowen C.R. , Strecker K. , Sabariz A.L.R.
Published: July 2010

This paper investigates the influence of processing parameters on the dielectric constant of compacted cementitious composites based on ordinary Portland cement and silica particles. A full factorial design was carried out to study the effects of size and shape of silica particles and uniaxial compaction pressures of 10 and 30 MPa on the dielectric constant and the apparent porosity of the composites. Silica particle size and compaction pressure were determined to be significant factors affecting the apparent porosity. The dielectric constant of the cementitious composite is significantly influenced by a combination of particle size, shape and compaction pressure.
The opaline silica-rich sedimentary rocks of Milos Island, Greece and their behaviour as pozzolanas in the manufacture of cement
Authors: Stamatakis M.G. , Fragoulis D. , Antonopoulou S. , Stamatakis G.
Published: July 2010

In the Pliocene–Pleistocene succession of Milos Island, Greece, siliceous rocks of biogenic origin (diatomites) occur interbedded with volcanic tuffs. Locally lava sills penetrate the diatomaceous rocks causing their diagenesis. In order to identify the nature of lava and related tuffites and the influence that lava intrusion had on the diatomaceous rocks, X-ray diffraction, scanning electrom microscopy, X-ray fluorescence and light microscopy analyses were performed on representative samples. The original diatomaceous rocks are mainly composed of opal-A in the form of broken diatom frustules and well preserved silicoflagellate skeletons. The affected diatomite beds are characterised as porcelanites containing neoformed opal-CT lepispheres, in expense of opal-A. To utilise the diatomites and porcelanite as pozzolanas, measurements on the Blaine, water demand and compressive strength of cements were carried out. Slightly lower strength was measured in porcelanite cement, due to the higher crystallinity of opal-CT compared to opal-A. However, both rocks improve the pozzolanic cement properties compared to that currently produced, using glassy tuffs.
Beam–spring model for timber diaphragm and shear walls
Authors: Pang W. C. , Rosowsky D. V.
Published: July 2010

A roof or floor diaphragm in a wood building generally spans across multiple lateral force-resisting elements (shear walls). The diaphragm serves as a horizontal beam that distributes forces to the shear walls. For design purposes, it is common to assume the wood diaphragm is either completely flexible or completely rigid. In North American low-rise light-frame wood construction, wood diaphragms are almost always designed as flexible diaphragms and are modelled as simple beams spanning across two adjacent shear walls. Strictly speaking, neither the flexible nor the rigid assumption is accurate for modelling the behaviour of a wood diaphragm. Full-scale shake table tests of a two-storey wood-frame structure, conducted as part of the NEESWood project, have confirmed that roof and floor diaphragms are semi-rigid. This paper examines the effect of diaphragm flexibility on shear wall deflections by considering the in-plane stiffness of the diaphragm to be semi-rigid. A beam–spring analogue model is used to represent the diaphragm–shear wall system where the shear walls are modelled as springs and the diaphragm is modelled as an analogue beam that acts as a load distribution mechanism. The resulting load sharing among the shear walls is examined and possible application of the beam–spring model to seismic design of wood-frame structures is discussed.
Slip modulus of inclined screws in timber–concrete floors
Authors: Symons D. , Persaud R. , Stanislaus H.
Published: July 2010

This paper presents a model for the stiffness of inclined screws used as shear connectors in timber and concrete composite floors. Screws inclined in the direction of slip have been shown to provide a higher stiffness (slip modulus) than vertically placed screws. An increased slip modulus per screw enhances the effective flexural stiffness of a partially composite timber and concrete beam, or, alternatively, allows the same flexural stiffness to be achieved with fewer screws. The model assumes that the screw behaves as a beam on a two-dimensional elastic foundation: it takes account of the inclination of the screw and models the timber as orthogonal springs with differing stiffnesses in the grain and transverse directions. The model also considers axial deformation, and hence shear lag, of the screw. Optimum inclination angle and embedment length of screw can be predicted. Preliminary validation of the model is provided by comparison with some experimental results.
Stiffness of dowel-type fasteners in timber–concrete joints
Authors: Dias A. M. P. G. , Cruz H. M. P. , Lopes S. M. R. , van de Kuilen J. W.
Published: July 2010

The mechanical behaviour of timber–concrete structures is significantly influenced by the stiffness of the joints, both with regard to deformations and to strength. This paper analyses the experimental and numerical assessment of the stiffness of timber–concrete joints, made with dowel-type fasteners. The objective of this analysis is to provide information to be used in the design of timber–concrete composite structures. In order to achieve this, two approaches were used: experimental tests with timber–concrete joints and numerical predictions using models available in the literature. As part of the experimental assessment, shear tests were performed with various joint configurations aiming to be representative of a wide range of practical conditions. The results obtained are presented and discussed. In terms of numerical assessment, two types of models were considered: analytical models, based on the beam on elastic foundation and empirical models. The results obtained in the experimental tests are compared with those obtained from the design models. Based on that analysis the accuracy of the numerical predictions is discussed.
The Effect of Rate and Date of Seeding of Small Grains on Yields
Authors: Woodward R. W.
Published: July 2010

Synopsis

On irrigated soil in Western U. S., barley sown at rates of 30 to 40 pounds per acre yielded as well as at higher rates up to 140 pounds per acre. Rates of 50 to 60 pounds were adequate for other grains except when sown late. Lighter rates produced stiffer straw, larger heads and kernels, and higher test weight per bushel than the heavier rates. At late planting dates, higher rates helped control weeds and disease. Use of high grade, certified seed is urged for higher yields at lower rates.
The Relation Between Precipitation, Temperature, and the Yield of Soybeans on the Agronomy South Farm, Urbana, Illinois1
Authors: Runge E. C. A. , Odell R. T.
Published: July 2010

Synopsis

Precipitation and maximum daily temperatures from June 25 through September 20 explained 68% of the variation in soybean yields from 1909 through 1957. Above‐normal precipitation during July (period of major vegetative growth) and from mid‐August to mid‐September (grain filling period) increased soybean yields, but abundant rainfall during other periods decreased yields. Maximum temperatures during July and August are too high for optimum soybean yields.
An Evaluation of the Thornthwaite and Mean Temperature Methods for Determining Potential Evapotranspiration1
Authors: Pelton W. L. , King K. M. , Tanner C. B.
Published: July 2010

Synopsis

Measurements of potential evapotranspiration indicate that mean temperature cannot be relied upon for general use in estimating evapotranspiration during short‐periods. Mean temperature methods can be used with limited success for long‐period (growing season and annual) estimates of potential evapotranspiration, but energy balance methods are preferable if radiation data are available.
Yield and Chemical Composition of Oats for Forage with Advance in Maturity1
Authors: Smith Dale
Published: July 2010

Synopsis

Percentages of protein, fat, ash, P, Ca, K, and nitrate declined with maturity while N.F.E. increased. Percent fiber increased until the heads emerged from the boot and then decreased. Yield of dry matter per acre was highest at near ripeness but a high proportion of the total yield of important nutritional constituents was produced at early dough stage.
Effect of Defoliation and Root‐Pruning on Early Root Growth from Merion Kentucky Bluegrass Sods and Seedlings1
Authors: Dunn J. H. , Engel R. E.
Published: July 2010

Two root observation container tests and a solution‐culture test were established to determine the effect of defoliation and root‐pruning on root initiation and development from ‘Merion’ Kentucky bluegrass (Poa pratensis L.) sod and seedlings.

The advantage of more rapid rerooting from sod and seedlings occurred with an increased amount of root removal as shown in three experiments. Sod pruned 1.3 cm thick gave an increased rate of root appearance and increased root density compared with thicker‐cut sod. Seedlings root‐pruned to 1 cm in solution culture regenerated roots more rapidly than those receiving less intense pruning.

Clipping tops to 3.8 cm and cutting sod thin (1.3 cm) was the best combination for early rooting of sods. Defoliation of sods to 0 cm as shown in two experiments caused early root inhibition but later increased root growth after a sufficient interval for recovery of top growth.

There was no association of carbohydrate content of tops and roots and root weights of sods at the conclusion of the root observation container experiments.
Movement of Three Herbicides in a Fine Sand Aquifer1
Authors: Schneider A. D. , Wiese A. F. , Jones O. R.
Published: July 2010

In order to determine movement of farm chemicals that might accidentally contaminate underground water supplies, low concentrations of three herbicides and NaNO3 as a tracer were injected into a sand aquifer through a dual‐purpose well. Herbicides used were picloram (4‐amino‐3,5,6‐trichloropicolinic acid), atrazine (2‐chloro‐4‐(ehylamino)‐6‐(isopropyl‐amino)‐s‐triazine), and trifluralin (α, α, α‐trifluoro‐2,6‐dinitro‐N, N‐dipropyl‐p‐toluidine). Recharge by injection continued for 10 days at an average rate of 81.8 m3/hour. After a 10‐day pause, the well was pumped for 12 days to determine if the herbicides and tracer could be recovered. Water samples were pumped from observation wells located 9, 20, and 45 m from the dual‐purpose well. Herbicides were detected in the 9‐ and 20‐m distant wells, but none of the herbicides or the tracer was detected in the 45‐m distant well. Picloram and atrazine moved freely through the aquifer, but some trifluralin adbsorbed to aquifer particles around the well. Although two herbicides moved freely from the point of injection, all of the chemicals were removed from the aquifer by pumping the contaminated water. Ninety‐three percent of the NO3 tracer and more than 91% of each herbicide were recovered with the pumped water. This study indicates that herbicides accidentally injected into a well in a relatively static aquifer can be recovered by pumping. Water could be utilized for irrigation of tolerant crops.
Seasonal Changes in Nonstructural Carbohydrate Levels and Innovation Number of Kentucky Bluegrass Turf Growing in Three Plant‐Climate Areas1
Authors: Younger V. B. , Nudge F. J. , Spaulding S.
Published: July 2010

Controlled environment studies have shown temperature to be one of the most important factors controlling nonstructural carbohydrate levels and density of Kentucky bluegrass (Poa pratensis L.) turf. Little information is available showing similar responses to temperature on a seasonal basis in the field. The objective of this experiment was to determine how nonstructural carbohydrate levels and density of Kentucky bluegrass turf differ among climatic areas and from season to season within an area. Total nonstructural carbohydrates (TNC) and innovation development were studied in five Kentucky bluegrass cultivars grown in the field in three distinct climate areas of California. These are a maritime climate of coastal southern California, a southern California interior valley thermal belt, and a temperate mountain valley. The respective soils of these areas are San Emigdio sandy loam classified as coarse‐loamy, mixed (calcareous), thermic Typic Xerofluvents; Arlington fine sandy loam classified as coarse‐loamy, mixed, thermic Haplic Durixeralf; and Havala sandy loam classified as fine‐loamy, mixed, thermic Typic Argixerolls. Results showed that changes in TNC levels and numbers of innovations followed seasonal patterns which were closely associated with the prevailing temperatures of each specific location. Consistently high summer temperatures reduced TNC stores but moderate temperatures did not affect them. Brief periods of exceptionally high temperature also reduced TNC levels. Accumulation of TNC occurred at each location at the time when temperatures were well below optimum for growth at that location. In the cold winter location, TNC levels decreased during the winter months. Flushes of growth occurring in spring depleted TNC. Density, the number of innovations per unit area, decreased throughout the summer at the high temperature location but increased through the cool winter. In the location of moderate summer and winter temperatures the number of innovations remained high and showed less seasonal fluctuation. Temperature, rather than day length, appeared to be the primary factor affecting innovation development.
Distribution and Growth of Sorghum Roots in Response to Irrigation Frequency1
Authors: Merrill S. D. , Rawlins S. L.
Published: July 2010

Root growth responds to alterations in timing and distribution of irrigation. In order to better understand crop response to irrigation regime, basic information is needed on the response of root growth, and in particular, root distribution, to differences of irrigation frequency. The lysimeter experiments reported here were designed to observe the growth of sorghum roots under conditions where soil temperature and bulk density were nearly invariant in time and over soil depth.

Grain sorghum (Sorghum bicolor (L.) Moench) was grown on Pachappa sandy loam soil (mixed thermic, coarse loamy, mollic Haploxeralf) in lysimeters with artificial lighting. Three irrigation frequencies were used. Soil strength was measured with a constant rate penetrometer on undisturbed cores from the lysimeters. Root length density was measured on soil samples taken five times during 76 to 79‐day growth periods. The relation between penetrometer soil strength (PSS) and matric potential (Ψ) was PSS = 3.717 − 21.52 Ψ (PSS in kg.cm−2, Ψ in bars), and for Ψ < −0.54 bar, PSS = 19.77 + 16.63 log10 (−Ψ). PSS, averaged over 12 to 14 day periods, differed by up to 20 kg.cm−2 from the upper to lower part of the profile in the least frequently irrigated treatment, in which part of the profile dried to −10 bars or less. In contrast, PSS variation with depth was no more than 2 kg.cm−2 under daily irrigation. While root penetration was as deep in the profile in all three treatments, root length density (cm . cm−3)was proportionally less in the upper profile of the less frequently irrigated treatments. The centroids of root length density profiles were located at a 10 to 15 cm higher depth under daily irrigation than under the least frequently irrigated treatment. Root length and dry weight yield were 20% to 30% higher under daily than under intermittent irrigation.

The difference between growth in the least frequently irrigated treatment and that in the daily‐irrigated at given depths correlated significantly with average PSS and log‐averaged matric potential. Within a given treatment there were almost no significant correlations between percentages of root growth at various depths and average PSS or log‐averaged matric potential. The relation between root growth and soil depth itself apparently obscurred these relations. It is concluded that PSS measurements, along with measurements of water, salt, and O2, status, will prove useful for interpreting the response of root growth to alteration of irrigation regime.
Field Evaluation of a Water Relations Model for Soybean. I. Validity of Some Basic Assumptions1
Authors: Zur B. , Jones J. W. , Boote K. J.
Published: July 2010

Basic assumptions made in a model of stomatal feedback control, transpiration, and carbon dioxide exchange rate (CER) were tested on soybean (Glycine max L. Merr cv. Williams) grown in the field on an Arredondo fine sand soil. Intensive measurements were made of diurnal fluctuations in leaf water potential, stomatal resistance, transpiration rate (TR), and canopy CER during a drying cycle corresponding to the mid‐to‐late pod‐filling period of the crop. A threshold leaf water potential initiating stomatal closure at −1.6 MPa was measured in the field and verified the relationship assumed in the model. Linear relationships between transpiration rate and both radiation flux and vapor pressure deficit were found to exist only in well‐watered plants having low stomatal resistances (1 to 3 sec/cm). Following the time when stomatal closure was initiated, the dependence of transpiration rate on climatic variables quickly dissipated. Transpiration rate was independent of stomatal resistance for fully open stomata, quickly decreased following stomata closure and remained essentially constant at high stomatal resistances. This overall behavior was satisfactorily described by a modified Penman equation which includes a stomatal resistance term. A curvilinear relationship between CER and photosynthetically active radiation flux (PAR) existed as long as stomata were fully open. Following stomata closure, CER was independent of PAR above 500 µ/m2‐sec (full sunlight = 2,100 µE/m2‐sec). The dependence of CER on stomatal resistance was similar to that of transpiration rate but with greater sensitivity.
Microclimate Effects on Toxaphene and DDT Volatilization from Cotton Plants1
Authors: Harper L. A. , McDowell L. L. , Willis G. H. , Smith S. , Southwick L. M.
Published: July 2010

Although the majority of chemicals used for insect control have low vapor pressures, the ability of these chemicals to vaporize is important in relation to possible efficacy reduction and their potential hazard as contaminants of nontarget areas. Micrometeorological methods were used to determine volatile losses of toxaphene (chlorinated Camphene) and DDT [1,1,1‐trichloro‐2,2‐bis(p‐chlorophenyl)ethane] from cotton (Gossypium hirsutum L.) plants under field conditions. Volatilization of the two insecticides from foliage was correlated best with air temperature and windspeed. Diurnal curves were developed for insecticide flux density, air temperature, windspeed, and net radiation. Peak air temperatures and windspeed coincided with peak flux densities in midafternoon whereas peak net radiation occurred 1 to 2 hours earlier. About 60 to 70 % of the mean daily flux occurred between 0600 and 1800 hours. Insecticide flux densities and the insecticide loads on the cotton plants decreased exponentially with time. The daily flux densities were about 3 to 5 % of the insecticide loads on the plants. The 50 %‐disappearance times (DT50) for toxaphene during mid‐growing season was 4.7 and 10.8 days later in the season. The DT50 for DDT was 10.3 days. The increase in surface soil pesticide loading during the study probably resulted from plant wash‐off, vapor‐phase movement downward from the plant foliage, and possibly mass movement in the evaporation stream from lower soil depths.
Denitrification Losses from Kentucky Bluegrass Sod
Authors: Mancino C. F. , Torello W. A. , Wehner D. J.
Published: July 2010

Denitrification may represent an important mechanism in the fate of N applied to turf. Denitrification losses were directly measured from fertilized ‘Baron’ Kentucky bluegrass (Poa pratensis L.) sod samples sealed in acrylic chambers using the acetylene inhibition technique. Losses were correlated with soil texture, percent soil saturation (SAT), and temperature. Losses from turf on a Hadley silt loam soil and Hadley silt soil (both coarse‐silty, mixed, nonacid, mesic Typic Udifluvents) incubated at 22°C did not exceed 0.4 and 0.1%, respectively, of the applied potassium nitrate fertilizer (4.5 g N m−2) when soil water levels were less than 75% saturated. Soil saturation increased denitriflcation losses from the silt loam and silt soils to 1.1 and 5.4% of the applied N, respectively. The relationship between percent soil saturation and denitriflcation loss was quadratic and highly significant for both soils. The equations are: milligrams of N2O–N m−2 10 d−1 = 1432.50 − 38.96 (percent SAT silt soil) + 0.26 (percent silt soil)2 or 130.80 − 5.40 (percent SAT silt loam soil) + 0.05 (SAT silt loam soil)2. A linear relationship [milligrams of N2O m−2 10 d−1 = 0.49(°C) − 9.70] existed between denitrification losses and soil temperatures between 11 and 30°C in the silt soil at 75% of soil saturation. Soil temperatures of 30°C or greater coupled with saturated soil conditions resulted in the greatest losses, equivalent to 44.6 and 92.6% of the applied N to the silt loam and silt soils, respectively. Denitrification losses did not increase at soil temperatures above 30°C. These results indicate that denitrification loss from fertilizers applied to turfgrasses may not be a serious problem unless the soils are saturated and at higher soil temperatures.
Comparison of the Trench‐Profile and Core Methods for Evaluating Root Distributions in Tillage Studies
Authors: Vepraskas M. J. , Hoyt G. D.
Published: July 2010

The trench‐profile method has not been widely used to evaluate root distributions in tillage studies because it is generally considered to be more of a qualitative than quantitative technique. The objective of this study was to determine if the trench‐profile method could be used to quantify and compare root development between tillage treatments as effectively as the widely used core method. Tobacco (Nicotiana tabacum L.) roots were evaluated for no‐till and strip‐till treatments on a Typic Hapludult, and corn (Zea mays L.) roots were evaluated for nonsubsoiled and subsoiled treatments on a Typic Paleudult. Distribution of roots with depth were generally similar between methods for a given site and treatment. Coefficients of variation at a given depth were similar between root count methods and increased from approximately 20% near the surface to over 120% at a depth of 1.0 m. For comparisons within a given site, significant (0.05 level) differences in root development between treatments were found at one site using the trench‐profile method, but no significant (0.10 level) differences were found at either site using the core method. Root data were significantly correlated (site r's were 0.89** and 0.87**) between root observation methods, but different relationships were found between study sites. Expressing root data on a proportional basis rather than as an absolute measure (root number or length) appeared suitable to equate data from the two methods. The number of man‐hours required to obtain root data by the trench‐profile method was about one‐fifth of that required to use the core method to obtain comparable amounts of data.
Cyst Nematode vs. Tolerant and Intolerant Soybean Cultivars
Authors: Radcliffe D. E. , Hussey R. S. , McClendon R. W.
Published: July 2010

The soybean cyst nematode (SCN), Heterodera glycines Ichinohe, is a major pathogen in soybean [Glycine max (L.) Merr.], and although resistant cultivars have been developed, new races of H. glycines build up that are capable of damaging the resistant cultivars. The use of tolerant and susceptible genotypes of soybean, which support SCN development and reproduction without serious plant growth reduction, is a promising method for limiting SCN yield suppression without creating selection pressure for new races of this nematode

A field study was conducted for 2 yr to determine the effect of SCN initial population (Pi) densities on soybean root and shoot development in the intolerant and susceptible cultivar, Bragg, and the moderately tolerant cultivar, Wright. Shoot and root growth was stimulated at the low Pi but reduced at high Pi in both years. Harvest seed weight showed a similar response in 1986, but declined steadily with increasing Pi in 1987 when there was less rainfall. The moderately tolerant cultivar, Wright appeared to be a smaller, more efficient plant than the intolerant cultivar, Bragg. Wright had a smaller root system than Bragg, but the roots in the top 0.15 m exhibited compensatory growth in response to early infection by SCN whereas Bragg root growth was suppressed. Wright also had a proportionately deeper root system, compared to Bragg, and this may be part of the mechanism of tolerance.
Ammonium Thiosulfate Effect on Herbicide Longevity in Soil
Authors: Goos R. J. , Ahrens W. H.
Published: July 2010

Soil‐applied herbicides often are mixed with liquid fertilizers to reduce application cost and increase time efficiency. Ammonium thiosulfate (ATS, 12‐0‐0‐268), a common liquid S fertilizer, can reduce microbial reaction rates in soil. The purpose of this study was to determine the influence of ATS on duration of effectiveness of soilapplied, microbially‐degraded herbicides. Greenhouse and growthchamber experiments were conducted using a coarse‐loamy Pachic Udic Haploboroll and a coarse‐silty Aeric Calciaquoll. The ATS at 0.3 to 0.38 mL kg‐1 soil extended the longevity of weed control by 2,4‐D [(2,4‐dichlorophenoxy)acetic acid], alachlor [2‐chloro‐,N‐(2,6,‐ diethylphenyl)‐N‐(methoxymethyl)acetamide], EPTC (S‐ethyl dipropylcarbamuthioate), cinmethylin [exo‐l‐methyl‐4‐(1‐methyIethyl)‐2‐[(2‐methylphenyl)methoxy]‐7‐oxabicyclo[2.2.l]heptane], and triallate [S‐(2,3,3‐trichloro‐2‐propenyl)bis(l‐methylethyl)carbamothioate]. The ATS had little effect on longevity of weed control by butylate [S‐ethyl bis(2‐methylpropyl)carbamothioate] or metolachlor [2‐chloro‐N‐(2‐methoxy‐1‐methylethyl)acetamide]. The lowest rate of ATS needed to extend 2,4‐D and EPTC efficacy was 0.15 mL kg−1 soil (about 8 gal A−1 or 26 kg S ha−1 assuming a tilled soil bulk density of 1.0 and a 5‐cm incorporation depth). This rate of ATS may be too costly for current use, but the concept deserves further evaluation because of the wide use of ATS and the need to extend the longevity of certain soil‐applied herbicides.
Performance of Randomized Block Designs in Field Experiments
Authors: Lin C. S. , Binns M. R. , Voldeng H. D. , Guillemette R.
Published: July 2010

Successful application of randomized block design in field experimentation depends on whether the blocking is done properly with respect to the direction of soil variation, and on whether plot variability within blocks is homogeneous. To investigate to what extent the first problem (orientation) causes inefficiency in the design, 60 sets uniformity trial data of soybean [Glycine max (L.) Merr] yield were used to investigate soil variation in one and two directions. The results show that the total sum of squares of soil variation attributable to one direction (taking the direction of the larger variation of row or column) was 39.3%, and to two directions was 52.7%. The difference of 13.4% reflects the fact that the blocking was not perpendicular to the direction of the soil variation. To study the second problem (heterogeneity within blocks) two sets of soybean data were used to compare various statistical techniques, namely:. (i) lattice design and analysis, (ii) fitting constants by position effects of rows and columns, (iii) covariate analysis by plot number, and (iv) neighbor analysis. The general conclusion is that when variability within blocks is homogeneous, a randomized block is satisfactory. However, if the plots are heterogenous then reanalyzing the data (ii) does reduce the error, but the average variance of difference is not as good as the standard (lattice) design, (i). In contrast, the analyses by (iii) and (iv) can result good precision as by lattice design.
Soybean Growth and Yield after Simulated Bean Leaf Beetle Injury to Seedlings
Authors: Hunt Thomas E. , Higley Leon G. , Witkowski John F.
Published: July 2010

Although the bean leaf beetle [Cerotoma trifurcata (Forster)] is a major pest of seedling soybean [Glycine max (L.) Merr.], the effects of beetle injury on soybean growth and yield are poorly understood. This study was conducted to characterize growth and yield responses of soybean to simulated bean leaf beetle injury occurring during seedling stages. Also, single‐day and sequential defoliation techniques were compared. The study was conducted on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll) in a soybean (‘Elgin 87’) field near Mead, NE. Treatments consisted of an undefoliated check and various levels (0‐80%) of simulated bean leaf beetle defoliation (sequential and single‐day) and/or cotyledon removal. Cotyledons were removed at stage VC, sequential defoliation was begun during stage V1, and single‐day defoliation was imposed on the last day of the defoliation period (late V3). Soybean yield significantly decreased 12% as seedling defoliation increased to 68%. Seedlings experiencing sequential defoliation did not reach a critical LAI of 3.5 until well into their reproductive stages, limiting light interception and dry matter accumulation. Cotyledon removal coupled with defoliation also reduced height up to 28% at R2.1 and delayed canopy development up to 11 d. Cotyledon removal reduced leaf area development of the seedling soybean 32%. Plants without cotyledons required up to 34% less defoliation than plants with cotyledons to delay canopy development and reduce yield. Single‐day defoliation techniques were less accurate than sequential defoliation techniques and overestimated the amount of leaf tissue a continuously defoliating insect would remove.
Infiltration and Soil Properties as Affected by Annual Cropping in the Northern Great Plains
Authors: Pikul Joseph L. , Aase J. Kristian
Published: July 2010

Fallow‐wheat (Triticum aestivum L.) cropping systems may be responsible for declines in soil organic matter and degradation of soil physical properties. A change to annual cropping may improve or at least maintain soil properties. Tillage and crop sequence effects on soil properties and water infiltration were tested after 9 yr of cropping on a Dooley sandy loam (fine‐loamy, mixed Typic Argiborolls) derived in glacial till. Annual cropping tillage of fall sweep and spring disk (AWFST), and no tillage (AWNT) were compared with conventional tillage in wheatfallow (FWCT) as the control. Statistical design was a randomized complete block with four replications. Soil samples were taken at 0.03−m increments to a depth of 0.3 m and were used to measure organic carbon (OC), pH, bulk density (BD), and particle size. Point resistance was measured in 0.02−m increments. Water infiltration into dry and wet soil was measured using a rainfall simulator. Maximum soil BD was 1.61 Mg m−3 on FWCT and 1.56 Mg m−3 on AWNT. Soil BD was not changed by one winter of freezing and thawing. Maximum point resistance was 2.2 MPa on FWCT and 1.7 MPa on AWNT. Cumulative 3‐h infiltration into dry soil was 52 mm for FWCT and 69 mm for AWNT. Final infiltration rate into wet soil was 5 mm h−1 for FWCT and 6 mm h−1 for AWNT. There was a significant difference in the depth distribution of OC between annual crop and FWCT treatments. Mass of OC in the top 0.09 m of soil was 1.65 kg m−2 on annual crop treatments and 1.45 kg m−2 on FWCT. Greater amounts of OC on the annual crop treatments compared with the FWCT attest to the beneficial aspect of annual cropping in maintaining a level of soil quality that is greater than FWCT. From a soil conservation perspective, no‐tillage has an additional advantage because surface cover is maintained throughout the year, thereby reducing the potential for soil erosion.
Deficit Irrigation of Cotton for Increasing Groundwater Use in Clay Soils
Authors: Cohen Y. , Plaut Z. , Meiri A. , Hadas A.
Published: July 2010

The interactive effects of a shallow, highly saline water table and irrigation management on crop production have not been clarified, due to difficulties in measuring crop water use. The detrimental effects of a rising water table and salinization due to irrigation can be eliminated, provided irrigation scheduling is based on a broad knowledge of crop water requirements. A deficit irrigation approach was used to (i) minimize deep percolation and (ii) study the capability of cotton (Gossypium hirsutum L.) to use water from the soil profile and from lower groundwater. Measurements of sap flow in the stem by the heat pulse method were used to determine transpiration. Transpiration of the mature cotton crop was nearly 20% lower than potential transpiration. Reduced irrigation application did not stimulate root expansion into wet, deep soil layers; therefore, it resulted in a reduction of the transpiration rate below its maximum rate. An appreciable water uptake from groundwater did not occur, presumably because of high sensitivity of the cotton root system to high soil density. Although the leaching fraction was nearly zero, salt accumulation in the root zone during the growing season was low.
Clipping Foliage Differentially Affects Phytosiderophore Release by Two Wheat Cultivars
Authors: Hansen Neil C. , Jolley Von D. , Brown John C.
Published: July 2010

Recent observations of grazing‐induced Fe‐deficiency chlorosis in wheat (Triticum aestivum L.) grown on calcareous soil indicates that Fe deficiency should be considered one of the factors associated with decreased grain yield in grazed wheat. Quantity of phytosiderophore release by roots of Fe‐deficient grasses has been closely linked to resistance to Fe‐deficiency chlorosis in numerous species and could potentially explain these observations. Phytosiderophore release following clipping was determined for two wheat cultivars (‘Abilene’ and ‘2157’) widely divergent in field chlorosis resistance. Plants were grown hydroponically in a complete nutrient solution containing 0.2 mg L−1 Fe as Fe‐HEDTA (N‐hydroxyethylethylenediaminetriacetic acid). Phytosiderophore release was measured using an Fe‐binding assay under nonaxenic conditions. Abilene and 2157 wheat responded differently to clipping of foliage. Initial response in both was reduced release of phytosiderophore, but the Fe‐chlorosis resistant cultivar (Abilene) responded to clipping by quick and complete restoration of the initially suppressed phytosiderophore, whereas the susceptible cultivar (2157) did not. Clipped Abilene released more phytosiderophore per gram of root than control plants on some days, but 2157 did not. Root growth was equally suppressed by clipping in both cultivars, compared with uncut control plants. Differential effect of defoliation on phytosiderophore release by these two cultivars helps explain some of the differences in Fe‐deficiency chlorosis resistance observed in the field. These results indicate that Fe‐chlorosis resistant wheat cultivars should be selected when managing wheat for both forage and grain production on calcareous soils.
Harvest Frequency and Cultivar Influence on Yield and Protein of Alfalfa‐Ryegrass Mixtures
Authors: Jung Gerald A. , Shaffer John A. , Everhart John R.
Published: July 2010

Binary mixtures of alfalfa (Medicago sativa L.) and perennial ryegrass (Lolium perenne L.) are commonly grown for forage in the U.S. Northeast. The competitiveness of ryegrass with alfalfa as modified by management practices has not been extensively studied. Two experiments were conducted to measure the influence of harvest frequency and ryegrass ploidy level on production, botanical composition, and crude protein concentration of alfalfa‐ryegrass mixtures. The first experiment used six replicates of a factorial treatment structure (three ryegrass cultivars × three harvest cycles) in a split‐plot design. The second experiment used three replicates of three cultivars × three harvest treatments. Increasing the length of the harvest cycle from 20 to 40 d increased alfalfa and total dry matter production (10.1 to 14.9 Mg ha−1) while decreasing ryegrass production and proportion (49 to 18%) of grass in the stand. Ryegrass was nearly eliminated from the stand at the 40‐d harvest cycle, but when the cutting cycle was changed to 20 d the next year, it became productive and contributed one‐fourth to one‐half of the total forage yield. Alfalfa, which had low productivity (7.3 to 8.4 Mg ha−1) in a 20‐d cycle, became very productive (16.4 to 17.4 Mg ha−1) when the cycle was changed to 40 d the next year. Crude protein concentration in alfalfa decreased from 248 to 200 g kg−1 as harvest cycle increased from 20 to 40 d. Ryegrass crude protein increased from 163 to 184 g kg−1 as harvest cycle increased. Frances and Diplomat perennial turfgrass ryegrasses were as productive and persistent as Citadel perennial forage ryegrass in binary mixtures with alfalfa.
Phenology and Tiller Characteristics of Big Bluestem and Switchgrass Cultivars in a Short Growing Season Area
Authors: Madakadze Ignacio , Coulman Bruce E. , Stewart K. , Peterson P. , Samson R. , Smith Donald L.
Published: July 2010

Warm‐season grasses are increasingly being cultivated in North America for summer forage and biomass production. The cooler temperatures and shorter growing seasons typical of Canadian production areas, are major limiting factors to warm‐season grass production in these areas. This research assessed the morphological development and relationship of growing degree‐days (GDD) to plant morphology and tiller characteristics in nine cultivars of switchgrass (Panicum virgatum L.; Blackwell, Cave‐in‐Rock, Dakota, Forestburg, Pathfinder, Shelter, Sunburst, ND3743, and New Jersey 50) and in ‘Niagara’ big bluestem (Andropogon gerardii Vitman). The study was conducted for three years on a St. Bernard sandy clay loam (Typic Hapludalf) in southwestern Quebec. Stand cover, plant morphology, tiller number, height, and diameter, and leaf number per tiller were all assessed during the season. All entries persisted through the three years of the study and showed increases in tiller number (from an average of 565 to 683 m−2) from one year to the next. Dakota, Cave‐in‐Rock, and Shelter switchgrass had the highest ground cover ratings after three years (85, 85, and 84%, respectively). Dakota, ND3743, and Forestburg were early maturing; New Jersey 50 was the latest in maturity. Niagara big bluestem had the tallest tillers (183 cm) and largest rates of increase in height (2.8 cm d‐1), followed by Cave‐in‐Rock (2.0 cm d−1) and Blackwell (1.9 cm d−1). The shortest tillers were recorded for Dakota (111 cm) and ND3743 (118 cm). Changes in leaf number per tiller with GDD were best described by quadratic regression models (r2 = 0.80‐0.97). These models were stable over two years. Cultivars varied in the number of GDD required for maximum number of leaves per tiller, with later‐maturing cultivars generally requiring greater GDD accumulation. These data indicate that warmseason grasses can be grown successfully in eastern Canada.
Glandular‐Haired Cultivars Reduce Potato Leafhopper Damage in Alfalfa
Authors: Sulc R. Mark , van Santen Edzard , Johnson Keith D. , Sheaffer Craig C. , Undersander Daniel J. , Bledsoe Larry W. , Hogg David B. , Willson Harold R.
Published: July 2010

Glandular‐haired alfalfa (Medicago sativa L.) cultivars developed for resistance to potato leafhopper [Empoasca fabae Harris] (PLH) have not been evaluated across a wide geographic area. Our objective was to evaluate forage growth, yield, insect damage, and stand density of glandular‐haired and standard alfalfa cultivars with and without insecticide control of naturally occurring PLH infestations across the Midwest USA. Nine glandular‐haired and five standard cultivars were evaluated from 1996 to 1998 in field experiments in Ohio, Indiana, Wisconsin, and Minnesota. Scheduled insecticide applications increased total yield of all cultivars, the response declining with increasing latitude (yield advantage = 32.7 − 0.72 × latitude; r2 = 0.86, P = 0.05). Depending on location, total yield loss due to PLH damage ranged from 5 to 23% for the standard cultivars and 1 to 10% for the glandular‐haired, commercially released cultivars (GR). Yield loss from PLH feeding in the GR cultivars was less than half of that observed in standard cultivars in environments where PLH stress was high. The GR cultivars yielded 1.1 Mg ha−1 more per year on average than the standard cultivars without insecticide under high PLH stress in Ohio and Indiana. Potato leafhopper nymph densities were lower in glandular‐haired cultivars than in standard cultivars. Cultivars had similar yield when treated with insecticide or when PLH populations were low. Glandular‐haired alfalfa cultivars were not immune to PLH damage; however, they can substantially reduce yield losses caused by this pest and provide a useful new tool for integrated pest management strategies.
Parameter Estimation for Crop Models
Authors: Wallach Daniel , Goffinet Bruno , Bergez Jacques-Eric , Debaeke Philippe , Leenhardt Delphine , Aubertot Jean-Noël
Published: July 2010

The adjustment of the parameters in mechanistic crop models to field data, using an automatic procedure, is essential to ensure efficient and objective use of measured data. However, it is in general numerically impossible, and in any case undoubtedly unwise, to adjust all the model parameters to the measured data. There is currently no widely accepted solution to this problem. This paper proposes a new approach to parameter adjustment, and applies it to a model of corn growth and development. One begins by defining a criterion of model goodness‐of‐fit, which should be adapted to the goal of the modeling exercise, and a corresponding criterion of model prediction error. For the latter we propose a cross validation version of the goodness‐of‐fit criterion. In Step 1 of the algorithm, one orders the parameters according to how much each improves the goodness‐of‐fit of the model. In the second step, the number of parameters actually adjusted is chosen to minimize the prediction error criterion. This approach has the advantage of explicitly using prediction quality as a criterion. As a by‐product, it leads to adjusting relatively few parameters (in our example, 3 out of the 26 potentially adjustable parameters), which considerably reduces the numerical problems. The procedure is quite straightforward to apply, although it does require substantial computing time.
Switchgrass Biomass Production in the Midwest USA
Authors: Vogel Kenneth P. , Brejda John J. , Walters Daniel T. , Buxton Dwayne R.
Published: July 2010

Information on optimal harvest periods and N fertilization rates for switchgrass (Panicum virgatumL.) grown as a biomass or bioenergy crop in the Midwest USA is limited. Our objectives were to determine optimum harvest periods and N rates for biomass production in the region. Established stands of ‘Cave‐in‐Rock’ switchgrass at Ames, IA, and Mead, NE, were fertilized 0, 60, 120, 180, 240, or 300 kg N ha−1. Harvest treatments were two‐ or one‐cut treatments per year, with initial harvest starting in late June or early July (Harvest 1) and continuing at approximately 7‐d intervals until the latter part of August (Harvest 7). A final eighth harvest was completed after a killing frost. Regrowth was harvested on previously harvested plots at that time. Soil samples were taken before fertilizer was applied in the spring of 1994 and again in the spring of 1996. Averaged over years, optimum biomass yields were obtained when switchgrass was harvested at the maturity stages R3 to R5 (panicle fully emerged from boot to postanthesis) and fertilized with 120 kg N ha−1. Biomass yields with these treatments averaged 10.5 to 11.2 Mg ha−1at Mead and 11.6 to 12.6 Mg ha−1at Ames. At this fertility level, the amount of N removed was approximately the same as the amount applied. At rates above this level, soil NO3–N concentrations increased.
Managing Soil Carbon and Nitrogen for Productivity and Environmental Quality
Authors: Sanchez Jose E. , Harwood Richard R. , Willson Thomas C. , Kizilkaya Kadir , Smeenk Jeffrey , Parker Elaine , Paul Eldor A. , Knezek Bernard D. , Robertson G. Philip
Published: July 2010

In this study, we investigated the impact of cropping system management on C and N pools, crop yield, and N leaching in a long‐term agronomic experiment in Southwest Michigan. Four management types, conventional (CO), integrated fertilizer (IF), integrated compost (IC), and transitional organic (TO) were applied to two crop sequences, a corn (Zea maysL.)–corn–soybean [Glycine max(L.) Merr.]–wheat (Triticum aestivumL.) rotation and continuous corn, which were grown with and without cover crops in the IF, IC, and TO managements. Using compost as a fertility source and reducing the use of herbicides and other chemicals resulted in long‐term changes in soil organic matter pools such TO ≥ IC > IF ≥ CO for total C and N and for the labile C and N measured through aerobic incubations at 70 and 150 d. Mineralizable N varied within the rotation, tending to increase after soybean and decrease after corn production in all systems. Corn yield was closely associated with 70‐d N mineralization potential, being greatest for first‐year corn with cover and least for continuous corn without cover under all management types. Although the TO and IC systems produced the lowest yield for second‐year or continuous corn, the combination of soybean and wheat plus red clover (Trifolium pratenseL.) always supported high yield for first‐year corn. Fall nitrate level and nitrate leaching were higher for commercially fertilized corn than for any other crop or for compost‐amended corn.