Spatial and Temporal Variability of Corn Grain Yield: Site-Specific Relationships of Biotic and Abiotic Factors

Inadequate information on factors affecting crop yield variability has contributed to the slow adoption of site-specific farming (SSF). This study was conducted to determine the effects of biotic and abiotic factors on the spatial and temporal variability of irrigated corn grain yields and to derive information useful for SSF. The effects of water (80% evapotranspiration (ET) and 50% ET), hybrid (drought-tolerant and -susceptible), elevation, soil index (SI)(texture), soil NO₃–N, arthropods, and diseases on corn grain yield were investigated at Halfway, TX on geo-referenced locations. Grain yields were influenced by interrelationships among biotic and abiotic factors. Grain yields were consistently high under high water treatment, at higher elevations, and on soils with high SI (high clay and silt). Soil NO₃–N increased grain yields when water was adequate. Management zones for variable rate fertilizer and water application should, therefore, be based on information on elevation, SI, and soil NO₃–N. The effects of arthropods, diseases, and crop stress (due to drought and N) on corn grain yield were unpredictable. Spider mite (Oligonychus pratensis) and common smut (Ustilago zeae) damage occurred under hot and dry conditions in 1998. Spider mite infestations were high in areas with high soil NO₃–N. Moderate air temperatures and high relative humidity in 1999 favored southwestern corn borer (Diatraea grandiosella) and common rust (Puccinia maydis) incidences. Knowledge of conditions that favor arthropods and diseases outbreak and crop stress can improve the efficiency of scouting and in-season management of SSF. Management of SSF can be improved when effects of biotic and abiotic factors on grain yield are integrated and evaluated as a system.     

The effect of foliar applied sulphur on individual glucosinolates in oilseed rape seed

The effect of foliar applied elemental sulphur on the individual glucosinolate content of oilseed rape seed was studied. Results show that the proportions of individual glucosinolates remained stable despite changes in the amount of sulphur applied, indicating that controlling sulphur availability cannot be used as a management tool to reduce the toxicity of rapeseed meal.     

Use of the ADVIA 120 for differentiating extracellular and intracellular hemoglobin

BACKGROUND: The use of cell-free hemoglobin (Hgb) solutions, such as Oxyglobin (Biopure Corp, Cambridge, MA, USA), as a blood substitute for the treatment of acute anemias is increasing in veterinary medicine. These solutions interfere with colorimetric tests, which do not discriminate between cellular Hgb (Hgb-cell) from the patient and extracellular Hgb (Hgb-delta) from the Oxyglobin, and therefore make the monitoring of anemia, based on Hgb concentration, difficult. The ADVIA 120 hematology analyzer (Bayer Diagnostics, Tarrytown, NY, USA) evaluates Hgb by 2 methods, a standard cyanmethemoglobin colorimetric method and flow cytometry, and therefore might provide the means to differentiate extracellular and intracellular Hgb. OBJECTIVE: The objective of this study was to determine the accuracy and precision of the ADVIA 120 in differentiating extracellular from intracellular Hgb. METHODS: Anticoagulated whole blood samples from 10 healthy dogs were analyzed in triplicate on the ADVIA 120. Hgb-delta concentration was determined by adding Oxyglobin (13 g/dL) to the whole blood samples at dilutions of 1:1, 1:2, 1:4, 1:8, 1:16, and 1:32. Hgb-cell and Hgb-total values were calculated and compared with actual values by linear regression. Analyses were done in triplicate and repeated 9 consecutive times to evaluate intra-assay precision of Hgb-total and Hgb-cell determinations. RESULTS: Correlation between Hgb values obtained by colorimetric (Hb-total) and flow cytometric (Hgb-cell) methods on whole blood samples was high (R(2) = .99; n = 10) with a slope of 0.96 and intercept of 0. Correlation between actual and predicted Hgb-cell values also was high (R(2) = .99), with a small positive bias (0.289 +/- 0.185; n = 60). Intra-assay precisions were high, with most coefficients of variation <2%. CONCLUSION: The ADVIA 120 is capable of differentiating Hgb-cell from Hgb-delta. The flow cytometric method is accurate and precise when compared with the cyanmethemoglobin method. A small bias between the results is unlikely to be clinically significant but may affect the ability of the ADVIA to differentiate small quantities (<0.3 g/dL) of Hgb-delta.     

Characterization and quantification of ceramides in the nonlesional skin of canine patients with atopic dermatitis compared with controls

As in humans, there is mounting evidence in support of an abnormal skin barrier contributing to the pathogenesis of canine atopic dermatitis (AD). Studies in people with AD have associated an abnormal skin barrier with deficiencies in ceramides, which represent important components of the stratum corneum (SC) intercellular lipid lamellae. Therefore, the goal of this study was to determine if the SC of dogs with AD is deficient in ceramides compared to normal dogs. Samples of SC were obtained from nonlesional skin of the caudal abdomen of 14 patients with AD and 14 age-, breed- and sex-matched healthy controls using a cyanoacrylate stripping procedure, and the subclass and relative amount of ceramides were assessed blindly by thin layer chromatography. Paired t -tests using R statistical computer software revealed the percentage amounts of ceramides 1 and 9 were significantly lower in nonlesional skin of AD dogs compared to controls ( P = 0.034 and P = 0.047, respectively), and the cholesterol percentage amount was significantly higher in AD dogs than in controls ( P = 0.016). Furthermore, the cholesterol/ceramide ratio was significantly higher in the AD group with respect to controls ( P = 0.014). These findings suggest that decreased amounts of ceramides in the skin of dogs with AD may be involved in the impaired barrier function of their skin.