Chipping performance of three processing potato cultivars during long-term storage at two temperature regimes

Three potato cultivars (Russet Burbank, Norchip, and Gemchip) grown with nitrogen applied at three rates were stored at two temperature regimes (Treatment 1: 13 months at 10 CTreatment 2: 1 month at 10 C; followed by a 1 C decrease per week until tubers were 4 C; followed by 6 months at 4 C; followed by a 1 C increase per week until tubers were 10 C; followed by 3 months at 10 C). Tuber chemical components and potato chip appearance were measured at harvest and after 3, 6, 9, 11, 12, and 13 months; these measurements were performed within 24 hours of the time potatoes were removed from storage. Sugar responses (tuber glucose, fructose, sucrose) and potato chip appearance were affected by cultivar over time in both years and storage temperatures. Russet Burbank tubers displayed a significantly higher glucose forming potential and produced darker appearing chips, regardless of storage temperature or time in storage, compared to Norchip and Gemchip. Potatoes receiving a cold-storage treatment contained less sugar and produced lighter appearing chips after 12 months storage compared to tubers stored at a constant 10 C for 12 months. The linear association between tuber chemical components and potato chip appearance varied with storage temperature.     

Estimation of repeatability of blood constituents in gestating beef cattle on protein- and energy-restricted diets

Repeatabilities of blood constituents were calculated for 104 Angus heifers on two separate experiments fed adequate, protein-deficient, energy-deficient, or both protein- and energy-deficient diets. Four statistical methodologies were compared including analysis of variance, principal component (structural) analysis based on the sample covariance and sample correlation matrix, and maximum likelihood. Of 12 blood constituents tested only seven were considered sufficiently important to be included in the analysis. These blood constituents included blood urea nitrogen (BUN), creatinine (Creat), alkaline phosphatase (Alk Phos), total protein (T Prot), total bilirubin (T Bil), cholesterol (Chol) and Iron (Fe). If the standard linear model assumptions were met for heifers on the adequate diet, the estimators appeared to be quite similar for both years except when the correlation coefficient was relatively small. If the assumption of homogeneity of the variance-covariance matrix (compound symmetry) was relaxed, the structural analysis method based on the sample correlation matrix appeared preferable. However, when combining all diets, the maximum likelihood methodology was preferred. Among the specific blood constituents, Alk Phos had the highest repeatability, not only for the heifers on the adequate diet, but also for heifers on other treatments in both years. Repeatabilities for T Prot appeared to be the most consistent over all rations in both years. Repeatability estimates for Fe were high and relative rankings were consistent for both years, while repeatabilities for the other variables were either low and(or) inconsistent.     

A NIR Technique for Rapid Determination of Soil Mineral Nitrogen

The objective of this investigation is to determine the possibility of rapidly sensing soil mineral-N content using near infrared (NIR) reflectance. Simulation studies were conducted to determine the ability of Partial Least Squares (PLS) and Principal Components Regression (PCR) techniques to relate NIR spectral data to soil nitrate content in the presence of interfering effects and experimental noise. The simulation studies revealed that both PLS and PCR techniques were quite robust in predicting soil nitrate content provided the calibration set included the same interfering effects. These techniques failed completely if the prediction set contained interfering effects which were not included in the calibration set. This implies that a site-specific calibration is necessary for this technique to work successfully. Laboratory tests using Yolo loam and Capay clay soil samples as well as verification tests using field soils (Yolo loam and Capay clay) mixed with nitrogen fertilizer indicated that soil mineral-N content can be determined using the NIR technique provided site-specific calibration is used.     

Comparison of seasonal development of tuber specific gravity among seven potato clones

Specific gravity of potato tubers provides an estimate of starch content of which uniformly high levels are important for product quality. The objectives of this study were to document the relationship between the level of specific gravity and the variability among tubers and to model the seasonal development o f specific gravity for seven potato clones. Individual determinations were made on twenty tubers from each plot using the weight-in-air, weight-in-water method on each of eight harvest dates spanning the tuber growth period. For each plot, the mean and standard deviation of specific gravity were calculated and used to define the correlation between specific gravity level and tuber-to-tuber variability and to construct a predictive model of the seasonal specific gravity developmental pattern. As the season progressed, tuber-to-tuber variability of specific gravity increased for some clones but not for others. A positive correlation existed between tuber specific gravity mean and its standard deviation for four of the seven clones in 1991 and five in 1992. Correlation coefficients were generally low, suggesting only a weak association between specific gravity and its standard deviation. Tuber specific gravity developed in a similar seasonal pattern for the seven clones. It generally started low, reached a maximum approximately seven to eleven weeks after tuberset, at which time some clones showed a tendency to decline through the remainder of the season. Quadratic regression equations provided an adequate model to describe specific gravity development for all seven clones over the tuber growth period. Statistical contrasts were used to test for differences in equation parameters, including line coincidence, line slope, and intercept. The model showed that initial specific gravity level at tuber set, the rate of early season increase, as well as the length of time from tuber set to specific gravity maximum, varied by clone and determined the level of specific gravity at season’s end.     

Long-Term Trends of Nitrogen and Phosphorus Use and Soil pH Change in Northern Idaho and Eastern Washington

Extension educates growers about using best management practices (BMPs) for nutrient management. However, it is important to understand grower management trends to prepare the best possible educational programs for growers. Three mail-based grower surveys conducted in 1981, 1996, and 2011 were used to document changing nitrogen (N) and phosphorus (P) fertilizer use and soil pH trends in the >450-mm precipitation zone of northern Idaho and eastern Washington, USA. The information collected in this paper spans a 40-year period. Nitrogen application rates have slightly increased, while P application rates on cereal crops have remained constant over the past 40 years. Average soil pH values have declined significantly over this time period; however, only about half of the surveyed growers were aware of this. This study is valuable because it (1) contains important information provided by growers on fertilization trends for the past 40 years (1971 to 2011), (2) quantifies the awareness of growers about soil pH decline in the region, and (3) provides baseline information, which can be used both in educational programming and to compare with future nutrient management.     

Use of foliar symptoms and plant height to predict yield loss in potatoes due to metribuzin injury

A model to predict yield loss due to metribuzin injury was developed using data from four experiments involving postemergence applications of metribuzin to numerous cultivars and breeding selections. Two explanatory variables, plant height proportion (PHR), defined as injured/uninjured, and percent foliar injury (FI), were used to predict yield loss. Three multiple regression models, including linear, quadratic, and a linear-log were considered and evaluated. Acceptance of the best model was based on comparison of fit as indicated by Residual Mean Squares, Adjusted R², and Predicted Sums of Squares. The best fit was for a linear-log model utilizing percent foliar injury and a natural log transformation of the plant height proportion (injured/uninjured). The predictive model was statistically validated by utilizing residual analysis on an independent data set. The model can be used to simply and quickly predict yield losses due to metribuzin injury     

Estimation of cardinal temperatures in germination data analysis

Seed germination is a complex biological process that is influenced by various environmental and genetic factors. The effects of temperature on plant development are the basis for models used to predict the timing of germination. Estimation of the cardinal temperatures, including base, optimum, and maximum, is essential because rate of development increases between base and optimum, decreases between optimum and maximum, and ceases above the maximum and below the base temperatures. Nonlinear growth curves can be specified to model the time course of germination at various temperatures. Quantiles of such models are regressed on temperature to estimate cardinal quantities. Bootstrap simulation techniques may then be employed to assure the statistical accuracy of these estimates and to provide approximate non parametric confidence intervals. A statistical approach to modeling germination and estimation of cardinal temperatures is presented with reference to replicated experiments designed to determine the effect of temperature gradient on germination of three populations of an introduced weed species, common crupina (Crupina vulgaris Per.).