bluuebunny/crossref_metadata_2025_split huggingface dataset:
Secondary dispersal, spatial dynamics and effects of herbicides on reproductive capacity of a recently introduced population of Bromus sterilis in an arable field
Authors: Steinmann H H , Klingebiel L 
Published: September 2004

SummaryAn arable field was subdivided and subjected to either deep inversion ploughing or non‐inversion cultivation after viable seeds of Bromus sterilis had been sown into oilseed rape stubble. After sowing in isolated plots distributed within the field, sequences of cropping treatments for the establishment of two successive winter wheat crops were applied. Each subfield was split into an uphill and a downhill direction for soil cultivation. The field had a 10° slope. In the season following seed introduction, 2.6% of the introduced seeds had successfully germinated and established in the non‐inversion cultivation regime, when no effective graminicide was applied. Ploughing eradicated B. sterilis. Using differential global positioning system (DGPS) mapping of the whole field population, emerged plants were observed up to 8.7 m (uphill treatment) and 21.3 m (downhill treatment) of their initial source. The median distance seeds were transported was 2.3 m uphill and 4.8 m downhill. Post‐emergence application of the herbicide propoxycarbazone slightly reduced weed density and seed weight, and almost halved weed seed production. Application of fenoxaprop‐P‐ethyl was followed by higher density of plants, tillers and seeds of B. sterilis. Seed viability was unaffected by herbicide use. Thus, in the second wheat crop following seed rain, the weed population was dispersed more widely in the field, such that 20–30% of seeds were dispersed more than 5 m distance from the first year's foci of infestation. The relevance of soil cultivation to secondary dispersal of B. sterilis is discussed.
Sorption–desorption of ‘aged’ isoxaflutole and diketonitrile degradate in soil
Authors: Bresnahan G A , Koskinen W C , Dexter A G , Cox L 
Published: September 2004

SummaryIsoxaflutole is a relatively new herbicide used for weed control in maize. The objective of this research was to increase the understanding of the behaviour and environmental fate of isoxaflutole and its diketonitrile (DKN) degradate in soil, including determination of the strength of sorption to soil and whether sorption is affected by ageing. In sandy loam (SL) and silty clay (SiCl) soils, 14C‐isoxaflutole was found to dissipate rapidly after application to soil; recovery ranged from ∼42% to 68% at week 0, and recovery had decreased to <10% at week 12. Decreases in 14C isoxaflutole residues over time in SL and SiCl soils are consistent with hydrolysis of isoxaflutole and formation of bound DKN residues in the soil. DKN recovery from freshly treated SiCl and SL soils was 41% to 52%. After a 12‐week incubation in SL soil at pH 7.1 and 8.0, recoveries were similar, ∼40%. However, at week 12 in SL soil pH 5.7, DKN recovery decreased to ∼28%. DKN recovery in SiCl soil at week 12 was <10%. Increases in sorption of DKN in SL at pH 5.7 and SiCl soil over time indicate that the DKN degradate is tightly bound to the soil and sorption is affected by soil pH and soil type. Sorption of 14C‐DKN in the SiCl soil more than doubled with ageing compared with the lower Kd sorption coefficient values of the SL soils. In the SiCl soil at time 0, the Kd was 0.6; at 1 week, Kd increased to 2; and at the end of the 12‐week incubation period, Kd was 4.5. This strong binding of DKN to the soil may be due to chelate formation in the interlayer of the clay.
Critical periods for weed control in cotton in Turkey
Authors: Bukun B 
Published: September 2004

SummaryField studies were conducted over 4 years in south‐eastern Turkey in 1999–2002 to establish the critical period for weed control (CPWC). This is the period in the crop growth cycle during which weeds must be controlled to prevent unacceptable yield losses. A quantitative series of treatments of both increasing duration of weed interference and of the weed‐free period were applied. The beginning and end of CPWC were based on 5% acceptable yield loss levels which were determined by fitting logistic and Gompertz equations to relative yield data representing increasing duration of weed interference and weed‐free period, estimated as growing degree days (GDD). Total weed dry weight increased with increasing time prior to weed removal. Cotton heights were reduced by prolonged delays in weed removal in all treatments in all 4 years. The beginning of CPWC ranged from 100 to 159 GDD, and the end from 1006 to 1174 GDD, depending on the weed species present and their densities. Practical implications of this study are that herbicides (pre‐emergence residual or post‐emergence), or other weed control methods should be used in Turkey to eliminate weeds from 1–2 weeks post‐crop emergence up to 11–12 weeks. Such an approach would keep yield loss levels below 5%.
Perspectives of Sorghum in Europe
Authors: Berenji J. , Dahlberg J. 
Published: September 2004

AbstractThis paper attempts to review the present status and offers a perspective on sorghum [Sorghum bicolor (L.) Moench] use and breeding in Europe. Topics such as botany, origin, utilization, agronomic performances and improvement of sorghum are discussed. Clearly, producers and users of sorghum should be more familiar with the crop so that they can take advantage of some of the unique characteristics that are associated with sorghum as it relates to Europe.
Protective Effects of Polyamines against Oxidative Stress Induced by Water and Cold Stress in Chickpea
Authors: Nayyar H. , Chander S. 
Published: September 2004

AbstractChickpea (Cicer arietinum L.) yields are drastically reduced by water and cold stress that occur individually or simultaneously in northern region of India. The comparative effects of both the stresses were investigated at the metabolic level by examining the endogenous status of polyamines (PAS), active oxygen species and antioxidants. Chickpea plants (15‐day old) growing hydroponically under controlled conditions (light/ dark; 24/21 °C, 16/8 h; irradiance 250 μmol m−2 s−1) were subjected to water deficit stress (Ψs of −0.2 to −1.0 MPa) and cold stress (5–25 °C) for 4 days. LD50 in terms of root growth rate (RGR), electrolyte leakage and triphenyl tetrazolium chloride (TTC) reduction activity was observed at −0.6 MPa and 10 °C for water and cold stress, respectively. In a subsequent experiment, 15‐day‐old plants were exposed to these stress levels under the above‐mentioned growth conditions for 7 days and analysed for various parameters. In cold‐stressed plants (CS), putrescine (PUT) was observed to be relatively higher while water‐stressed plants (WS) had more of spermidine (SPD). Spermine (SPM) levels increased more rapidly in WS and declined on the fourth day of stress while in CS, a gradual increase occurred that decreased on the seventh day. The accumulation of PAs was short‐lived under the combined presence of both the stresses. Hydrogen peroxide elevated abruptly in WS and remained higher than CS while the latter showed a marked increase in malondialdehyde content. Ascorbic acid increased sharply in WS that decreased on the fourth day while CS showed a relatively gradual increase that reached its maximum on the fourth day and declined subsequently. Glutathione was significantly higher in CS plants in comparison with WS and CS + WS plants. The activity levels of superoxide dismutase were higher up to 4 days and declined subsequently while those of WS stayed higher till the last day of stress. Ascorbate peroxidase levels were significantly higher in CS plants while catalase activity was comparatively more in WS. Exogenous application of PAs reduced the level of hydrogen peroxide, malondialdehyde content and raised the level of antioxidants. Put caused 44 and 32 % increase in RGR in CS and WS, respectively, while SPD resulted in 110 and 25 % enhancement in WS and CS, respectively. Under combination of stresses, RGR increased by 21, 53 and 10 % by Put, SPD and SPM, respectively. The effects of PAs could be reversed largely by their biosynthetic inhibitors. α‐difluoromethylornithine (a biosynthetic inhibitor of putrescine) caused more damage to CS while cyclohexylamine (inhibitor of SPD and SPM biosynthesis) was more inhibitory in WS.
Productivity and Sustainability of Cotton (Gossypium hirsutum L.)–Wheat (Triticum aestivum L.) Cropping System as Influenced by Prilled Urea, Farmyard Manure and Azotobacter
Authors: Das A. , Prasad M. , Shivay Y. S. , Subha K. M. 
Published: September 2004

AbstractField experiments were conducted at Indian Agricultural Research Institute, New Delhi, during 2001–2002 and 2002–2003, to study the effect of inorganic, organic and Azotobacter combined sources of N on cotton (Gossypium hirsutum L.) and their residual effect on succeeding wheat (Triticum aestivum L.) crop. The results indicated considerable increase in yield attributes and mean seed cotton yield (2.33 Mg ha−1) with the combined application of 30 kg N and farmyard manure (FYM) at 12 Mg ha−1 along with Azotobacter (M4). The treatment in cotton that included FYM, especially when fertilizer N was also applied could either improve or maintain the soil fertility status in terms of available N, P and K. Distinct increase in yield attributes and grain yield of wheat was observed with the residual effect of integrated application of 30 kg N ha−1 + FYM at 12 Mg ha−1 + Azotobacter. Direct application of 120 kg N ha−1 resulted 67.4 and 17.7 % increase in mean grain yield of wheat over no N and 60 kg N ha−1, respectively. Integrated application of organic and inorganic fertilizer is therefore, recommended for higher productivity and sustainability of the cotton–wheat system.
Root and Shoot Growth of Maize (Zea mays) as Affected by Incorporation of Crotalaria juncea and Tithonia diversifolia as Green Manures
Authors: Sangakkara U. R. , Liedgens M. , Soldati A. , Stamp P. 
Published: September 2004

AbstractCrop establishment, determined by shoot and root growth during early growth is a vital component in procuring desired plant populations and high yields in rainfed tropical smallholder farming systems, where green manures help maintain soil fertility and sustainability. As green manure incorporation could affect early seedling growth, studies were conduced in a plant house using soils from fields, to evaluate the impact of incorporating two popular tropical green manures (Crotalaria juncea and Tithonia diversifolia) into soil under rainfed field conditions over 3 years, on selected physico‐chemical properties of the soils and on establishment and early shoot and root growth of maize (Zea mays), with and without inorganic fertilizers. In a given year, green manure was grown in one season while maize was grown in the other. A soil that did not receive green manures but was left fallow during the period of green manure cultivation was used as the control treatment. The incorporation of green manures over the 3 years showed trends of increasing soil physical properties, and also the available nitrogen, phosphorus and potassium contents. Incorporation of Crotalaria, with its higher nitrogen content, promoted shoot growth, while Tithonia induced the development of an extended root system. The use of inorganic fertilizers stimulated the beneficial impact of the green manures in promoting shoot and root growth. The use of green manures, especially Tithonia, promoted the development of seminal and nodal roots of maize seedlings, both in the form of length and thickness (based on root surface area) and root length densities, which could assist in successful crop establishment and resource utilization, rather than primary roots. The benefits of using green manures, especially Tithonia, in promoting root growth and Crotalaria in shoot development of maize seedlings even without inorganic fertilizers is presented.
Nitrogen Loss and Wheat (Triticum aestivumL.) Yields in Response to Zero‐tillage and Sowing Time in a Semi‐arid Tropical Environment
Authors: Patra A. K. , Chhonkar P. K. , Khan M. A. 
Published: September 2004

AbstractA net‐house experiment was conducted at the Indian Agricultural Research Institute, New Delhi, to study the effect of simulated zero‐tillage on the N loss through ammonia (NH3) volatilization, and flux of inorganic N after the sowing of wheat and urea‐N application on two different dates. In addition, the effects of soil perturbation through simulated tillage vs. zero‐tillage, and of sowing time on the wheat yields (above and below‐ground) and N use were examined. Results showed significantly (P < 0.05) higher NH3volatilization loss of N in zero‐tillage than the tillage treatments, but no significant difference between early (18 November) or later (8 December) sowing wheat on such losses. Inorganic N, mostly NH‐N, was significantly higher in undisturbed soil on day 5, whereas on day 15, NO‐N was significantly higher in disturbed soil than the undisturbed (zero‐tilled) soil. There was little difference in NH‐N or NO‐N contents in soils between two dates of sowing. Plant parameters showed no significant (P > 0.05) differences among the treatments in terms of height, spike length, or number of grains per spike, grain and straw yields and root biomass and harvest index. Moreover, there were no significant differences among the treatments when N uptakes were compared. Our results thus suggest that after flooded rice, wheat can be grown successfully on zero‐tilled soils even when adopting sowing dates till early December. More N loss through NH3volatilization in zero‐tilled than tilled soils may not affect growth and yields of wheat, but needs to be reduced for N conservation and environmental reasons.
Prediction in linear mixed models
Authors: Welham Sue , Cullis Brian , Gogel Beverley , Gilmour Arthur , Thompson Robin 
Published: September 2004

SummaryFollowing estimation of effects from a linear mixed model, it is often useful to form predicted values for certain factor/variate combinations. The process has been well defined for linear models, but the introduction of random effects into the model means that a decision has to be made about the inclusion or exclusion of random model terms from the predictions. This paper discusses the interpretation of predictions formed including or excluding random terms. Four datasets are used to illustrate circumstances where different prediction strategies may be appropriate: in an orthogonal design, an unbalanced nested structure, a model with cubic smoothing spline terms and for kriging after spatial analysis. The examples also show the need for different weighting schemes that recognize nesting and aliasing during prediction, and the necessity of being able to detect inestimable predictions.
Fitting and comparing seed germination models with a focus on the inverse normal distribution
Authors: O'Neill Michael E. , Thomson Peter C. , Jacobs Brent C. , Brain Phil , Butler Ruth C. , Turner Heather , Mitakda Bernadetha 
Published: September 2004

SummaryThis paper reviews current methods for fitting a range of models to censored seed germination data and recommends adoption of a probability‐based model for the time to germination. It shows that, provided the probability of a seed eventually germinating is not on the boundary, maximum likelihood estimates, their standard errors and the resultant deviances are identical whether only those seeds which have germinated are used or all seeds (including seeds ungerminated at the end of the experiment). The paper recommends analysis of deviance when exploring whether replicate data are consistent with a hypothesis that the underlying distributions are identical, and when assessing whether data from different treatments have underlying distributions with common parameters. The inverse normal distribution, otherwise known as the inverse Gaussian distribution, is discussed, as a natural distribution for the time to germination (including a parameter to measure the lag time to germination). The paper explores some of the properties of this distribution, evaluates the standard errors of the maximum likelihood estimates of the parameters and suggests an accurate approximation to the cumulative distribution function and the median time to germination. Additional material is on the web, at http://www.agric.usyd.edu.au/staff/oneill/.
Performance of localized regression tree splitting criteria on data with discontinuities
Authors: Bremner Alexandra P. , Taplin Ross H. 
Published: September 2004

SummaryProperties of the localized regression tree splitting criterion, described in Bremner & Taplin (2002) and referred to as the BT method, are explored in this paper and compared to those of Clark & Pregibon's (1992) criterion (the CP method). These properties indicate why the BT method can result in superior trees. This paper shows that the BT method exhibits a weak bias towards edge splits, and the CP method exhibits a strong bias towards central splits in the presence of main effects. A third criterion, called the SM method, that exhibits no bias towards a particular split position is introduced. The SM method is a modification of the BT method that uses more symmetric local means. The BT and SM methods are more likely to split at a discontinuity than the CP method because of their relatively low bias towards particular split positions. The paper shows that the BT and SM methods can be used to discover discontinuities in the data, and that they offer a way of producing a variety of different trees for examination or for tree averaging methods.
Testing for the presence of disease by pooling samples
Authors: Kennedy Nyongesa L. 
Published: September 2004

SummaryScreening of pooled urine samples was suggested during the Second World War as a method of detecting syphilis in US soldiers. Recently, pooling has been used in screening blood for Human Immunodeficiency Virus (HIV) antibody to help curb the further spread of the deadly virus. Pooling reduces the cost and also reduces the rates of false‐negative results in samples that are not disease‐free, a factor that has led to pooling not being adopted as an efficient procedure for screening HIV. This paper generalizes a common pooling strategy with retesting, and discusses its characteristics. Furthermore, it suggests a new testing strategy with retesting.
Mid‐P confidence intervals based on the likelihood ratio for proportions estimated by group testing
Authors: Hepworth Graham 
Published: September 2004

SummaryGroup testing has been used in many fields of study to estimate proportions. When groups are of different size, the derivation of exact confidence intervals is complicated by the lack of a unique ordering of the event space. An exact interval estimation method is described here, in which outcomes are ordered according to a likelihood ratio statistic. The method is compared with another exact method, in which outcomes are ordered by their associated MLE. Plots of the P‐value against the proportion are useful in examining the properties of the methods. Coverage provided by the intervals is assessed using several realistic grouptesting procedures. The method based on the likelihood ratio, with a mid‐P correction, is shown to give very good coverage in terms of closeness to the nominal level, and is recommended for this type of problem.
Assessing goodness‐of‐fit of categorical regression models based on case‐control data
Authors: Zhang Biao 
Published: September 2004

SummaryDemonstrated equivalence between a categorical regression model based on case‐control data and an I‐sample semiparametric selection bias model leads to a new goodness‐of‐fit test. The proposed test statistic is an extension of an existing Kolmogorov–Smirnov‐type statistic and is the weighted average of the absolute differences between two estimated distribution functions in each response category. The paper establishes an optimal property for the maximum semiparametric likelihood estimator of the parameters in the I‐sample semiparametric selection bias model. It also presents a bootstrap procedure, some simulation results and an analysis of two real datasets.
Detection of a change point with local polynomial fits for the random design case
Authors: Huh J. , Park B.U. 
Published: September 2004

SummaryRegression functions may have a change or discontinuity point in the ν th derivative function at an unknown location. This paper considers a method of estimating the location and the jump size of the change point based on the local polynomial fits with one‐sided kernels when the design points are random. It shows that the estimator of the location of the change point achieves the rate n−1/(2ν+1) when ν is even. On the other hand, when ν is odd, it converges faster than the rate n−1/(2ν+1) due to a property of one‐sided kernels. Computer simulation demonstrates the improved performance of the method over the existing ones.
Multi‐sample inference for simple‐tree alternatives with ranked‐set samples
Authors: Ozturk Omer , Wolfe Douglas A. , Alexandridis Roxana 
Published: September 2004

SummaryThis paper develops a non‐parametric multi‐sample inference for simple‐tree alternatives for ranked‐set samples. The multi‐sample inference provides simultaneous one‐sample sign confidence intervals for the population medians. The decision rule compares these intervals to achieve the desired type I error. For the specified upper bounds on the experiment‐wise error rates, corresponding individual confidence coefficients are presented. It is shown that the testing procedure is distribution‐free.To achieve the desired confidence coefficients for multi‐sample inference, a nonparametric confidence interval is constructed by interpolating the adjacent order statistics. Interpolation coefficients and coverage probabilities are provided, along with the nominal levels.
Estimating the population median using only a central subset of observations
Authors: Huang J.S. , Lin G.D. 
Published: September 2004

SummaryIn estimating the population median, it is common to encounter estimators which are linear combinations of a small number of central observations. Sample medians, sample quasi medians, trimmed means, jackknifed (and delete‐d jackknifed) medians and jackknifed quasi medians are all familiar examples. The objective of this paper is to show that within this class the quasi medians turn out to have the best asymptotic mean squared error.
Buehler confidence limits and nesting
Authors: Kabaila Paul , Lloyd Chris J. 
Published: September 2004

SummaryThe Buehler 1 –α upper confidence limit is as small as possible, subject to the constraints that its coverage probability is at least 1 –α and that it is a non‐decreasing function of a pre‐specified statistic T. This confidence limit has important biostatistical and reliability applications. Previous research has examined the way the choice of T affects the efficiency of the Buehler 1 –α upper confidence limit for a given value of α. This paper considers how T should be chosen when the Buehler limit is to be computed for a range of values of α. If T is allowed to depend on α then the Buehler limit is not necessarily a non‐increasing function of α, i.e. the limit is ‘non‐nesting’. Furthermore, non‐nesting occurs in standard and practical examples. Therefore, if the limit is to be computed for a range [αL, αU]of values of α, this paper suggests that T should be a carefully chosen approximate 1 –αL upper limit for θ. The choice leads to Buehler limits that have high statistical efficiency and are nesting.