SIMULATION STUDY OF SPATIAL-POISSON DATA ASSESSING INCLUSION OF SPATIAL CORRELATION AND NON-NORMALITY IN THE ANALYSIS

Spatial correlation and non-normality in agricultural, geological, or environmental settings can have a significant effect on the accuracy of the results obtained in the statistical analyses. Generalized linear mixed models, spatial models, and generalized linear models were compared in order to assess how critical the inclusion of non-normality and spatial correlation is to the analysis. Spatially correlated data with a Poisson distribution were generated in a completely randomized design (CRD) with 2 treatments and 18 repetitions. Four analyses: spatial Poisson, non-spatial Poisson, spatial normal, and non-spatial normal, were conducted on the simulated data to compare their power functions. The degree of spatial correlation, size of the mean, the dimension of the plots and difference between the two treatment means were altered to investigate how the ability to detect differences between the treatments is affected. In addition, the range covariance parameter was estimated and compared among the spatial models. Some covariance parameter estimates were under-estimated. The size of the field plot and the treatment means were increased to assess their effects on estimation of the range. The Reduced Maximum Likelihood (REML) covariance parameter estimates were compared to those obtained using Maximum Likelihood (ML) estimates. The analysis that incorporated the spatial correlation of the observations and used ML to estimate the covariance parameters had the highest power and most accurate range parameter estimates

PREDICTING SOIL TEMPERATURES IN HIGH TUNNELS USING A DYNAMIC MODEL BASED ON NEWTONIAN LAW OF COOLING

High tunnels are low cost temporary greenhouses that are often used to extend the growing season for high value crops such as tulips, muscari, sweet pea cultivars, and hyacinth beans. Profitability depends on selection and timing of crops to optimize use of these structures. Predicting soil temperatures in high tunnels as a function of outside temperature is a critical factor in crop selection and timing. However, predicting soil temperatures is difficult because air temperatures constantly change from hour to hour and day to day. We develop a model to account for temperature dynamics in high tunnels by modifying the fundamental differential equation in Newtonian law of cooling. We fit the model to data from high tunnels located in two states - Nebraska, Kansas and predict soil temperature as a function of external air temperatures. The model fits reasonably well at all high tunnel stations with most predictions being within 2° C of the observed value. We also found that the model could be used to adequately predict soil temperatures at one site based on parameter estimates of another nearby site. Thus we conclude that the model is an adequate tool in making high tunnel placement decisions and is useful for selection and timing of crops within established high tunnels

Dietary Fiber in Sow Gestation Diets - An Updated Review

Twenty-four published reports dating from 1975 to 2007 were examined to determine the overall effects of feeding gestation sows additional fiber. Sow and litter traits among trials were weighted by the number of litters for each treatment within each trial. Overall, sows can successfully consume high-fiber diets during gestation with few deleterious effects. Positive effects from feeding high-fiber diets were evident in litter size (0.2 to 0.6 pigs/litter) and sow lactation feed intake (0.5 to 0.8 lb/day), but they are not largely evident until the second reproductive cycle following exposure to the diet. It\u27s possible that to ensure sow and litter performance improvements from feeding fiber, fiber must be included in the diet before mating

Correlation of Omega-3 Fatty Acids Intakes with Acculturation and Socioeconomic Status in Midwestern Latinas

Background: Low socioeconomic status (SES) and acculturation of Latino immigrants in the U.S. are linked to a decrease in diet quality. Methods: Interviews were conducted with 162 first-generation Latinas to examine the association of SES and acculturation with intake of omega-3 (n − 3) fatty acids. Each participant provided dietary intake by use of a validated n − 3 food frequency questionnaire administered twice, 4 weeks apart, three 24-h recalls, sociodemographic information and completed the 5-item Short Acculturation Scale. Results: Mean intakes of Total n − 3, α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (g/d) were 1.2 ± 0.7, 1.1 ± 0.6, and 0.1 ± 0.1, respectively. After adjusting for energy intake, education was significantly correlated with EPA + DHA intakes, and acculturation was significantly correlated with Total n − 3, ALA and EPA + DHA intakes. Foods sources of EPA + DHA eaten by at least 50% of participants were chicken, shrimp, tuna and eggs. Discussion: Given the beneficial cardiovascular effects of n − 3 fatty acids, it is important to understand sociocultural factors affecting adequate intake towards an improvement in diet quality in minorities