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Edmonton, Canada

Little research has been conducted on the effect of mowing and buffer width on the effectiveness of short-width (<10 m) native grass buffers to filter sediment, nutrients, and bacteria. A 2-yr (2011-2012) field study was conducted on native rangeland in southern Alberta. The treatments of mowing and buffer width (1.5, 3, 6 m) were evaluated using a randomized complete block design with four replicates. The buffer plots were pre-wet with distilled water. A spiked solution was then applied to each plot using a run-on distribution device and the runoff collected every 10 min for 30 min once the runoff started discharging from the plot. The volume of runoff, and percent reduction in concentration and mass of sediment [total dissolved solids (TSS)], phosphorus [dissolved reactive P (DRP), total P], nitrogen (total N), and bacteria (Escherichia coli, total coliforms) in runoff were determined. The findings did not support our hypothesis that percent reductions in concentrations and mass for sediment, nutrients, and bacteria were greater for mowed than unmowed buffers. In contrast, the findings supported our hypothesis that increasing buffer width would significantly (P ≤0.05) decrease mass (but not concentration) of sediment, nutrients, and bacteria in runoff. The significant mass reduction was attributed to a reduced runoff ratio caused by longer residence time and greater infiltration in the wider buffers. Mass reductions for the three buffer widths ranged from 29 to 92% for TSS, 22 to 93% for DRP, 38 to 93% for total P, 23 to 92% for total N, and between 61 and 94% for E. coli and total coliforms. These findings suggest that buffer width but not mowing may reduce runoff quantity and improve runoff quality over the short term. © 2015, Routledge. All rights reserved. Source

Walker D.J.,University of Manitoba | Wiseman G.,Agri Food Canada | Belcher B.,Royal Roads University | Dewi S.,International Center for Research in Agroforestry | And 2 more authors.
Canadian Journal of Remote Sensing

Image speckle is inherent in synthetic aperture radar (SAR) data resulting in difficulty interpreting raw radar imagery and necessitating some form of image enhancement. A wide variety of filter types are available to reduce speckle and a number of univariate or subjective methods have been proposed to evaluate their efficacy. However, there are few multivariate criteria to evaluate optimal filter type and kernel size in the analysis of multi-image datasets. Optimal selection of both is especially critical when the target features approach the pixel size of the radar images. In this study, we present principal component analysis and multiple discriminate analysis as quantitative multivariate approaches to evaluate filter performance, primarily focusing on speckle suppression in multitemporal multi-incident angle SAR datasets. We also examine application of these criteria to a texture-based filter. Five common filtering techniques are evaluated to determine which filter type and size maximized the multivariate redundancy and discrimination of classes in radar data in Kalimantan Timur, Indonesia. We found the performance of all filters increased rapidly for small kernels, but they approach a maximum after which little improvement occurs with size. Of the filters examined, the Gamma filter (11×11 kernel size) was optimal based on the multivariate criteria and, although not statistically significant, was able to detect forest age in regenerating dry rice fields (ladang). © 2011 CASI. Source

Karamanos R.E.,Viterra Ltd | Selles F.,Agriculture and Agri Food Canada | James D.C.,Agri Food Canada | Stevenson F.C.,142 Rogers Road
Canadian Journal of Plant Science

The ability of fallow to supply nitrogen (N) to crops has been questioned, particularly for crops with greater N requirements. A study was conducted to determine canola (Brassica napus L.) and wheat (Triticum aestivum L.) responses to a range ofNfertilizer rates (0-75 kg Nha-1 for canola and 0-50 kgN ha-1 for wheat) at 17 fallow sites across Saskatchewan and Alberta, Canada, from 2003 to 2005. Yield and N uptake responses to progressively greater Nfertilizer rates were curvilinear for both crops. Maximum yield occurred with 76 kgNha-1 for canola yield (2190 kg ha-1) and 47 kgNha-1 for wheat (2910 kg ha-1). MaximumNuptake occurred at about 90 kgNha-1 for both crops. Wheat grain yield and N uptake responses were mostly associated with normalized difference vegetation index (NDVI) at anthesis or flag leaf, whereas canola yields and N uptake were most associated with NDVI at five-leaf or bolting, or Cardy Nitrate meter at bolting. The preceding relationships were most apparent at the highestNfertilizer rates. Canola and wheat water use were not affected by N fertilizer rate, but water use efficiency increased linearly for both crops as N fertilizer rate was increased. Source

Reiss K.,University of Tubingen | Kirchner E.,University of Tubingen | Kirchner E.,Institute Pasteur Paris | Gijzen M.,Agri Food Canada | And 6 more authors.
Journal of Biological Chemistry

Transglutaminases (TGases) are ubiquitous enzymes that catalyze selective cross-linking between protein-bound glutamine and lysine residues; the resulting isopeptide bond confers high resistance to proteolysis. Phytophthora sojae, a pathogen of soybean, secretes a Ca 2+-dependent TGase (GP42) that is activating defense responses in both host and non-host plants. A GP42 fragment of 13 amino acids, termed Pep-13, was shown to be absolutely indispensable for both TGase and elicitor activity. GP42 does not share significant primary sequence similarity with known TGases from mammals or bacteria. This suggests that GP42 has evolved novel structural and catalytic features to support enzymatic activity.Wehave solved the crystal structure of the catalytically inactive point mutant GP42 (C290S) at 2.95Åresolution and identified residues involved in catalysis by mutational analysis. The protein comprises three domains that assemble into an elongated structure. Although GP42 has no structural homolog, its core region displays significant similarity to the catalytic core of the Mac-1 cysteine protease from Group A Streptococcus, a member of the papain-like superfamily of cysteine proteases. Proteins that are taxonomically related to GP42 are only present in plant pathogenic oomycetes belonging to the order of the Peronosporales (e.g. Phytophthora, Hyaloperonospora, and Pythium spp.) and in marine Vibrio bacteria. This suggests that a lateral gene transfer event may have occurred between bacteria and oomycetes. Our results offer a basis to design and use highly specific inhibitors of the GP42-like TGase family that may impair the growth of important oomycete and bacterial pathogens. © 2011 by The American Society for Biochemistry and Molecular Biology, Inc. Source

Elliot T.R.,University of Guelph | Reynolds W.D.,Agri Food Canada | Heck R.J.,University of Guelph

This study investigates the use of 3D soil pore characteristics (volume, surface area, and tortuosity) for prediction of saturated hydraulic conductivity (Ks). The pore characteristics were determined by cluster labeling of X-ray CT images and random-walk simulations of 3D pore space. The flow characteristics of the four soil cores were measured in the laboratory pre- and post-CT imaging. The predicted values of Ks were arrived at through the use of Darcy's equation and a modified Poiseuille equation. For comparison the 2D pore characteristics were determined from individual slice of X-ray CT imagery, and fed into three established methods of predicting Ks. The predicted Ks by the proposed method exhibited a positive correlation to both pre- and post-imaging measured Ks, and attained a greater correlation than the 2D Ks prediction. © 2010 Elsevier B.V. All rights reserved. Source

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