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The mineralization effect of wheat straw on soil properties described by MFPC analysis and other methods

Abstract

Recycling of crop residues is essential to sustain soil fertility and crop production. Despite the positive effect of straw incorporation, the slow decomposition of that organic substance is a serious issue. The aim of the study was to assess the influence of winter wheat straws with different degrees of stem solidness on the rate of decomposition and soil properties. An incubation experiment lasting 425 days was carried out in controlled conditions. To perform analyses, soil samples were collected after 7, 14, 21, 28, 35, 49, 63, 77, 91, 119, 147, 175, 203, 231, 259, 313, 341, 369, 397 and 425 days of incubation. The addition of two types of winter wheat straw with different degree of stem solidness into the sandy soil differentiated the experimental treatments. The results demonstrate that straw mineralization was a relatively slow process and did not depend on the degree of filling of the stem by pith. Multivariate functional principal component analysis (MFPC) gave proof of significant variation between the control soil and the soil incubated with the straws. The first functional principal component describes 48.53% and the second 18.55%, of the variability of soil properties. Organic carbon, mineral nitrogen and sum of bases impact on the first functional principal component, whereas, magnesium, sum of bases and total nitrogen impact on the second functional principal component.

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Computing Bayes factors to measure evidence from experiments: An extension of the BIC approximation

Summary

Bayesian inference affords scientists powerful tools for testing hypotheses. One of these tools is the Bayes factor, which indexes the extent to which support for one hypothesis over another is updated after seeing the data. Part of the hesitance to adopt this approach may stem from an unfamiliarity with the computational tools necessary for computing Bayes factors. Previous work has shown that closed-form approximations of Bayes factors are relatively easy to obtain for between-groups methods, such as an analysis of variance or t-test. In this paper, I extend this approximation to develop a formula for the Bayes factor that directly uses information that is typically reported for ANOVAs (e.g., the F ratio and degrees of freedom). After giving two examples of its use, I report the results of simulations which show that even with minimal input, this approximate Bayes factor produces similar results to existing software solutions.

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On determination of ETL – a distributional approach

References Eubank R. (1988): Spline Smoothing and Nonparametric Regression. Marcel Dekker, New York. Afzal M., Yasin M., Sherawat S.M. (2002): Evaluation and Demonstration of Economic Threshold Level (ETL) for Chemical Control of Rice Stem Borers Scirpophagaincertulus Wlk . And S.innotata Wl. International Journal of Agriculture and Biology 3: 323-325. Simonoff J. (1995): Smoothing Methods of Statistics. Springer. New York. Thisted R.A. (1988): Elements of Statistical Computing

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Determination of robust optimum plot size and shape – a model-based approach

Summary

Determination of optimum plot size has been regarded as an important and useful area of study for agriculturists and statisticians since the first remarkable contribution on this problem came to light in a paper by Smith (1938). As we explore the scientific literature relating to this problem, we may note a number of contributions, including those of Modjeska and Rawlings (1983), Webster and Burgess (1984), Sethi (1985), Zhang et al. (1990, 1994), Bhatti et al.(1991), Fagroud and Meirvenne (2002), etc. In Pal et al. (2007), a general method was presented by means of which the optimum plot size can be determined through a systematic analytical procedure. The importance of the procedure stems from the fact that even with Fisherian blocking, the correlation among the residuals is not eliminated (as such the residuals remain correlated). The method is based on an application of an empirical variogram constructed on real-life data sets (obtained from uniformity trials) wherein the data are serially correlated. This paper presents a deep and extensive investigation (involving theoretical exploration of the effect of different plot sizes and shapes in discovering the point – actually the minimum radius of curvature of the variogram at that point – beyond which the theoretical variogram assumes stationary values with further increase in lags) in the case of the most commonly employed model (incorporating a correlation structure) assumed to represent real-life data situations (uniformity trial or designed experiments, RBD/LSD).

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Impact of cereal diseases on the qualitative traits of spring barley breeding lines

.F., Jensen H.P., Ostergard H. (1995): A Japanese powdery mildew isolate with exceptionally large infection efficiency on Mlo-resistant barely. Plant Pathology. 44: 786- 790. Mila A.L. Carriquiry A.L. Yang X.B. (2004): Modeling the prevalence of Sclerotinia stem rot of soybeans in the North Central region of the United States. Phytopathology. 94: 102-110. Rao C.R., Toutenburg H. (1999): Linear Models. 2nd ed. Springer-Verlag New York. Statkevičiūtė G., Leistrumaitė A. (2010): Modern varieties of spring barley as a genetic

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