Physical Sciences and Mathematics Commons^™

2004 Forage Spokesperson Contestants, James Chestnut, Jimmy May, Steve Meredith, Bill Payne

Kentucky Grazing Conference

No abstract provided.

Strategies For Reducing Stored Feed Requirements, Don Ball

Kentucky Grazing Conference

A basic, desirable goal for virtually any livestock producer is to minimize stored feed requirements. It is less expensive to have livestock harvest forage for themselves by grazing than to harvest it for them; therefore, the greater the extent to which pasture can be used to provide nutrition, the more profitable a livestock operation will generally be. Thus, it is worthwhile to consider all options that might be available for reducing stored feed needs.

Stocking Decisions: They Make Or Break You, Glen E. Aiken

Kentucky Grazing Conference

Decisions on species and variety of forage to plant and manage are economically critical because it establishes the potential to meet a particular production goal. However, the stocking rate used to graze these forages is more critical because it ultimately determines if a targeted level of production is reached. Most cattlemen aim for a stocking rate that provides maximum economic return, but it should be emphasized that an economically optimum stocking rate is one that potentially provides sustained economic return. It is obvious that dollar return is not maximized if excessive heavy grazing results in costly pasture renovation, ranging from …

Grazing: Getting From Where You Are To Where You Want To Be, Gary Bates

Kentucky Grazing Conference

When trying to design a forage and grazing program, producers often try to consider so many factors that it becomes mind-boggling. If basic plant physiology, how and when a forage plant grows is considered, improving a forage program will usually become easier, especially in developing a controlled grazing system. The purpose of a controlled grazing system should be to improve the utilization of the high quality forage produced on the farm. In order to improve this utilization, it is helpful to understand plant growth and quality, and the factors that affect them.

Will Improved Grazing Pay For Extra Fencing And Water Cost?, Ken Johnson

Kentucky Grazing Conference

Expectation is founded on faith, and in faith lays opportunities. I suppose as we look at most farming operations most changes occur from force not by choice. What I propose today and hope to convince most of you; is that here is an opportunity to make more profit, if you’re willing to change and have faith that it will work. Most of us have heard of, if not practiced rotation grazing for a long time. The question many ask, is it worthwhile. Does better grazing management make me any more money? I hope to at least provide some insight as …

Present And Future Tall Fescue Varieties, Timothy D. Phillips

Kentucky Grazing Conference

Tall fescue has played a key role in forage production over the past century in the USA. It has other uses besides forage applications, such as turf, mine reclamation, and highway rights-of-way, but in this presentation we will focus on forage varieties. Several hundred turf-type tall fescue varieties have been developed over the past 30 years, mainly by private seed companies using material from Reed Funk at Rutgers University in New Jersey. Forage varieties aren’t as numerous. I will discuss some of the older and current forage tall fescue varieties, and finish by discussing the newest varieties, and those that …

Fertilizing Pastures For Profit, Byron Sleugh

Kentucky Grazing Conference

It has been known for centuries that providing certain nutrients to plants is critical for high productivity. The nutrient source and manner in which it is applied may vary, but the desired outcome is the same: high crop yield and quality. Fertilization is the most practical means that producers have to ensure that crops receive the nutrients they need. While increasing fertilizer application and managing pH by liming can lead to increase forage production, your investment should be measured against the potential return. Also, over application of nutrients can potentially cause environmental problems.

Role Of Legumes In Pasture Systems, Garry D. Lacefield

Kentucky Grazing Conference

Successful livestock programs are dependent on forage programs which supply large quantities of adequate quality, homegrown feed. A major percentage of the feed units for beef (83%) and dairy (61%) cattle come from forages. In addition, forages supply an estimated 91%, 72%, 15% and 99% of the nutrients consumed by sheep and goats, horses, swine and ruminant wildlife, respectively. These values can be put in perspective when we consider that 63% of Kentucky's Agricultural Cash Receipts are from livestock and livestock products. Cash hay accounts for approximately 28% of the total crop value. Hay ranks second only to tobacco in …

Foreword And Kfgc Award Winners [2004], Garry D. Lacefield, Christi L. Forsythe

Kentucky Grazing Conference

No abstract provided.

A Comparison Of Geostatistical And Spatial Autoregressive Approaches For Dealing With Spatially Correlated Residuals In Regression Analysis For Precision Agriculture Applications, Ignacio Colonna, Matías Ruffo, Germán Bollero, Don Bullock

Conference on Applied Statistics in Agriculture

Regressions such as Grain yield=f(soil,landscape) are frequently reported in precision agriculture research, and are typically computed using conventional OLS methods, implicitly ignoring spatial correlation of the residuals. This oversight can have a marked effect on the final conclusions derived from these regressions. A further issue is, which approach should be used to account for this problem? We investigated this question using a 2 year data set that includes sitespecific soil and topographic information and soybean yields and compare regression results from direct covariance representation and spatial autoregressive approaches. Our results show that the coefficients from both spatial approaches are in …

Distribution Of Boll Number And Lint Yield By Time And Position In Upland Cotton Cultivators, Jixiang Wu, Johnie N. Jenkins, Jack C. Mccarty Jr.

Conference on Applied Statistics in Agriculture

The time period and position which make the major contribution to total yield and to its variation is important for the field management and breeding for upland cotton, Gossypium hirsutum, L. Two-year end-of-season plant mapping data from 11 upland cotton cultivars were analyzed by position and by week. The data showed that the first position in the second and third weeks made the largest contribution to the total boll number and lint yield. The eleven cultivars differed with respect to the earliness but they had similar lint yield at harvest. The early season cultivars produce more yield and more …

Identification Of Errors In Cotton Fiber Data Sets Using Bayesian Networks, G F. Sassenrath, J. E. Boggess, Xintong Bi, H. C. Pringle

Conference on Applied Statistics in Agriculture

Cotton fiber is graded on a series of parameters based on physiological factors (strength, length, and thickness), lint color, and presence of non-lint matter such as leaves, stems or other foreign materials. Cotton lint is graded by the USDA-AMS after harvest and ginning, and the grade determines the price of the lint. Given the importance of cotton fiber quality to the value of the crop, the spatial variability of cotton fiber properties is of particular interest to researchers and producers in developing management scenarios for optimal profitability. Previous research studies have relied on hand-harvesting the cotton at intervals throughout the …

Conditioning Plots And Designed Experiments, Jeffrey S. Pontius, John W. Slocombe, John E. Boyer, Jr.

Conference on Applied Statistics in Agriculture

Conditioning plots (coplots) are useful graphics for displaying values of response variables conditional on the values of given (conditioning) variables. We present a principles guide for construction of coplots when the data or statistics come from studies based on designed experiments, and illustrate the usefulness of these coplots in interpreting results. We have found coplots to be useful in our statistical consulting work, and illustrate our approach so that others may find them useful. Coplots in traditional and in trellis displays are provided.

An Example Of Developing Covariates For Problems In Precision Agriculture, D. W. Meek, J. W. Singer

Conference on Applied Statistics in Agriculture

Methodology for precision agriculture is, perhaps, too focused on methods that allow for spatial correlation in the ANOVA error term. While sound inference about differences between local yields can be computed, no understanding of what is driving these differences is achieved. A completely general form for a spatial model can include suitable covariates. Most research in precision agriculture includes gathering a variety of site-specific information. Through the presentation of the analysis of data from a published soybean [Glycine max (L.) Merr.] study, one specific type of covariate is developed - a duration index for soybean canopy light interception over …

Nonlinear Models With Repeated Measures For Analyzing Disease Progress In Plant Epidemiology, R. Macchiavelli, W. Robles, E. Abreu, A. Pantoja

Conference on Applied Statistics in Agriculture

Nonlinear models are commonly used in plant disease epidemiology to model temporal changes in the proportion of diseased plants (disease index). Most of the times they are fit using linearizing transformations or nonlinear least squares. These approaches assume that the disease index has a normal distribution, that they are independent and that they have constant variance. None of these assumptions can be justified in disease indices. In this paper we apply different strategies to model the progress of papaya ring spot virus in papaya. Using the logistic model we compare different strategies using the SAS® System. Marginal (population average) and …

Hotelling’S T2 Approximation For Bivariate Mixed (Dichotomous & Continuous) Data, Imad Khamis, Pradeep Singh, James Higgins

Conference on Applied Statistics in Agriculture

The comparison of the means of two treatments or populations when more than one variable is measured may be done using Hotelling’s T² statistic. In many real world situations the data obtained are mixed, i.e. one variable is dichotomous and the other variable is continuous. The assumption of multivariate normality upon which Hotelling’s T² is based is no longer valid. In this paper, an approximate Hotelling T² test is proposed for bivariate mixed data and empirically evaluated in terms of Type I error rate. It is shown that the approximation does a good job of controlling the …

Analyzing Binomial Data In A Split-Plot Design: Classical Approaches Or Modern Techniques?, Liang Fang, Thomas M. Loughin

Conference on Applied Statistics in Agriculture

Binomial data are often generated in split-plot experimental designs in agricultural, biological, and environmental research. Modeling non-normality and random effects are the two major challenges in analyzing binomial data in split-plot designs. In this study, seven statistical methods for testing whole-plot and subplot treatment effects using mixed, generalized linear, or generalized linear mixed models are compared for the size and power of the tests. This study shows that analyzing random effects properly is more important than adjusting the analysis for non-normality. Methods based on mixed and generalized linear mixed models hold Type I error rates better than generalized linear models. …

Comparing Analyses Of Unbalanced Split-Plot Experiments, Christina D. Smith, Dallas E. Johnson

Conference on Applied Statistics in Agriculture

Several procedures for constructing confidence intervals and testing hypotheses about fixed effects in unbalanced split-plot experiments have previously been presented and discussed by Remmenga and Johnson. They recommended a few of the procedures they considered as useful and reliable procedures. Since the advent of the SAS® MIXED procedure, mixed model analyses with REML estimates of the variance components are easily accessible to researchers. This paper compares the analysis of unbalanced split-plot experiments using mixed model procedures with REML estimates of the variance components to the previously established procedures by means of additional simulation studies.

Estimating Rheological Properties Of Yogurt Using Different Versions Of The Freundlich Model And Design Matrices, M. Zhou, A. M. Parkhurst, H. K. Voss, C. L. Weller

Conference on Applied Statistics in Agriculture

The rheological properties described by the consistency coefficient and flow behavior index can be estimated from the relationship between shear stress and shear strain rate following a Freundlich model. An additional rheological property of concern to food scientists studying yogurt is yield stress. They extend the Freundlich model to include a three-parameter model called the Herschel-Bulkley model. In addition, the Herschel-Bulkley model is often linearized by taking logarithms of both sides. An additional complication is the viscometer limits the range of shear strain rates. The objectives of this study are to compare parameter estimates from the three models and to …

Statistical Analysis Of 70-Mer Oligonucleotide Microarray Data From Polyploid Experiments Using Repeated Dye-Swaps, Hongmei Jiang, Jianlin Wang, Lu Tian, Z. Je Rey Chen, R. W. Doerge

Conference on Applied Statistics in Agriculture

Polyploidy plays an important role in plant evolution. A series of Arabidopsis autopolyploids and allopolyploids have been developed, and their transcript abundance compared using a 70-mer oligonucleotide microarray consisting of 26,090 annotated genes in Arabidopsis thaliana. The experimental design included repeated dye-swaps, and analysis of variance (ANOVA) was employed to detect significant gene expression changes among and between the diploid, autopolyploid, and allopolyploid populations. Here, we discuss the statistical issues (replication, normalization, transformation, per-gene variance estimate, and the pooled estimate of variation) involved in analyzing these data, as well as the statistical findings of these analyses.

Introduction To Bayesian Quantitative Trait Locus Analysis For Polyploids, Dachuang Cao, Bruce A. Craig, R. W. Doerge

Conference on Applied Statistics in Agriculture

Quantitative Trait Locus (QTL) mapping in polyploids is complicated by the un-observable parental QTL con guration, especially the number of copies (dosage) of the QTL. Existing techniques estimate the parental QTL con guration using a profile likelihood approach and do not address the uncertainty in the estimates. In this paper, a Bayesian method is proposed to jointly model the parameters including the parental QTL configuration, QTL location, and QTL effects. Inference for parameters is obtained by integrating the posterior distribution of the parameters via a Markov chain Monte Carlo (MCMC) sampler, which is a hybrid of the Metropolis-Hastings, Gibbs, and …

Some Results On The Design Of Experiments For Comparing Unreplicated Treatments, R. J. Martin, J. A. Eccleston, N. Chauhan, B. S. P. Chan

Conference on Applied Statistics in Agriculture

In early generation variety trials, large numbers of new varieties may be compared, and little seed is usually available for each variety. A so-called unreplicated trial has each new variety on just one plot at a site, but includes several (often around 5) replicated check or control (or standard) varieties. The total proportion of check plots is usually between 10% and 20%. The aim of the trial is to choose some (around 1/3) good performing varieties to go on for further testing, rather than precise estimation of their mean yield.

Now that spatial analyses of data from field experiments are …

Statistical Analysis Software For Multiplicative Interaction Models, Eun-Joo Lee, Dallas E. Johnson

Conference on Applied Statistics in Agriculture

In a two-way cross-classified experiment, one is almost always interested in whether the two factors interact or not. When there are no independent replications, there are no traditional tests for interaction. This research considers the problem of analyzing a two-way cross-classified experiment using multiplicative interaction models when there are no independent replications and interaction between the two factors may exist. The purpose of this research is to develop SAS® macros to provide user-friendly statistical software for the analysis of interaction in two-way experiments. The macros also provide many useful graphical displays including displays to help one determine the pattern of …

Automatic Model Selection In The Mixed Models Framework, Matthew Kramer

Conference on Applied Statistics in Agriculture

Stepwise model selection is a commonly used technique in regression when there are many candidate independent variables and limited time to develop a model. This approach was adapted to the mixed models framework and gives good results, established by simulation with a known model and by application to real world data. Model selection is done using an information criterion (selected by the user). The application is primarily written in Perl. The Perl code tracks which variables are in or out of the model, calculates the information criterion, and writes and submits SAS code. Proc Mixed in SAS is used to …

The Onset, Cessation, And Rate Of Growth Of Loblolly Pines In The Face Experiment, Susanne Aref, David J. Moore, Evan H. Delucia

Conference on Applied Statistics in Agriculture

The Duke Forest FACE experiment was set up to investigate the impact of elevated CO₂ levels on a larger eco system. One of the studies dealt with the impact of elevated CO₂ levels on the onset and cessation of growth of loblolly pine trees (Pinus taeda L.). In this study the times of these events were determined for each year, 1996 - 2002. The rate of growth, the growth duration, and actual growth were determined from the models of onset and cessation of growth. Adjusted for initial basal area, the rate of growth, the actual growth, …

Genetic Mapping Of Gene Expression Levels: Expression Level Polymorphism Analysis For Dissecting Regulatory Networks Of Plant Disease Resistance, Kyunga Kim, Marilyn A. L. West, Richard W. Michelmore, Dina A. St. Clair, R. W. Doerge

Conference on Applied Statistics in Agriculture

The genetic basis of inherited traits has been studied through di erent approaches in many areas of science. Examples include quantitative trait locus (QTL) analysis and mutant analysis in genetics, genome sequencing and gene expression analysis in genomics. Each of these approaches is used for the investigation of complex traits, such as disease resistance, but also provides knowledge on components of complex biological systems. We introduce a novel functional genomics approach that integrates two areas, genetics and genomics, by applying QTL analysis to quantitative di erences in the mRNA abundance of trait-related genes. This approach allows comprehensive dissection of regulatory …

Prediction Of Yellow Starthistle Survival And Movement Over Time And Space, Fei Tian, Bahman Shafii, Christopher J. Williams, Timothy S. Prather, William J. Price, Lawrence W. Lass

Conference on Applied Statistics in Agriculture

Yellow starthistle is a noxious weed that has become a serious plant pest with devastating impact on ranching operation and natural resources in western states. Early detection of yellow starthistle and predicting its spread has important managerial implications and greatly reduce the economic losses due to this weed. The dispersal of yellow starthistle consists of two main components, plant survival and seed movement. Resources and direct factors relating to these components are not typically available or are difficult to obtain. Alternatively, topographic factors, such as slope, aspect and elevation, are readily available and can be related to plant survival and …

Information Technologies And The Design And Analysis Of Site-Specific Experiments Within Commercial Cotton Fields, J. L. Willers, G. A. Milliken, C. G. O’Hara, J. N. Jenkins

Conference on Applied Statistics in Agriculture

Information products derived from multi-spectral remote sensing images, LIDAR elevations, or data products from other sensor systems (soil electrical conductivity measurements, yield monitors, etc.) characterize potential crop productivity by mapping biophysical aspects of cropland variability. These sensor systems provide spectral, spatial, and temporal measurements at resolutions and accuracies describing the variability of in-field, physical characteristic phenomena, including management practices from cropland preparation, selection of crop cultivars, and variable-rate applications of inputs. In addition, DGPS-equipped (differential, global positioning system) harvesters monitor yield response at closely spaced, georeferenced points. Geographic information system and image processing techniques fuse diverse information sources to spatially …

A Comparison Of Spatial Prediction Methods Using Intense Spatially-Acquired Water Quality Data, E. Barry Moser, Victor H. Rivera-Monroy, Ariel R. Alcantara-Eguren

Conference on Applied Statistics in Agriculture

Water quality information obtained through intensive spatial sampling using automated devices provides opportunities to monitor and forecast the spatial distribution of nutrients and phytoplankton concentrations, and help establish water circulation patterns in estuarine and coastal waters. To be cost effective, efficient sampling designs and estimation methodologies must first be developed. As a starting basis, we applied an original transect sampling design that was used to estimate the spatial distribution of chlorophyll a, salinity, and temperature in the Cienaga Grande de Santa Marta, a coastal lagoon in Colombia. We superimposed the transects over satellite images of the lagoon obtained in the …

Random Models With Direct And Competition Genetic Effects, L. , D. Van Vleck, J. P. Cassady

Conference on Applied Statistics in Agriculture

Livestock producers often select for animals which are genetically superior for yield. Competition among animals in the same pen may affect yield of pen mates. If competitiveness has a genetic component, selection should be for direct genetic effects for yield and for genetic effects of competitiveness on yield of penmates (Muir and Schinkel, 2002). This simulation study examined estimates of variance components from models which ignored competition effects. A population structure of 642 related animals was created. Random effects were residual and pen effects and direct and competition genetic values with genetic correlation. Conclusions, based on 400 replications for 16 …