Digital images for assessing soil cover of crop plants

The main drawback by using crop soil cover in weed harrowing research is that it is assessed by visual scores, which are biased and context dependent. This problem may be solved by using digital image analysis. In this paper a new image capture standard and digital image analysis procedure was used to illustrate three key issues in relation to weed harrowing; selectivity, resistance and recovery. All issues require reliable assessments of crop soil cover. Crop soil cover was deduced from assessments of leaf cover, which is defined as the proportion of pixels in digital images determined to be green. Objective assessments of leaf cover and crop soil cover showed that the selectivity of weed harrowing in winter wheat and spring barley was unaffected by timing within a two weeks interval. Crop recovery, defined as the ability of the crop to recover from soil cover was determined in winter wheat and highly influenced by timing of weed harrowing. Increasing intensities of harrowing in growth stage (BBCH) 22 in winter wheat increased crop yields whereas crop yields declined by increasing intensities in growth stage 23 due to differences in the crop recovery capacity. Resistance defined as the capacity of the crop to resist soil cover was tested in barley, field pea and mixtures of barley and field pea. No differences were found between the crops. Future aims in mechanical weed control research are discussed in the context of the availability of unbiased crop soil cover data

TOLERANCE OF CEREALS TO POST- EMERGENCE WEED HARROWING

This study defines crop tolerance to post-emergence weed harrowing as the combined effect of crop resistance and crop recovery. Crop resistance is the ability of the crop to resist soil covering and recovery is the ability to recover in terms of yield. In two experiments, resistance, recovery and tolerance were quantified in barley, oat, wheat and triticale by a new method based on digital image analysis. Important differences in resistance, recovery and tolerance among species were seen and resistance was not linked to recovery. Oat showed higher resistance than wheat, and barley. Triticale showed the lowest resistance. Oat and barley showed both lower ability to recover from soil covering than wheat, and triticale showed complete recovery. Triticale was the most tolerant species followed by wheat, oat and barley. Differences in tolerance caused species dependent crop yield losses in weed-free environments in the range of 0 to 10% for a practical relevant aggressiveness of weed harrowing

Assessment of leaf cover and crop soil cover in weed harrowing research using digital images

Objective assessment of crop soil cover, defined as the percentage of leaf cover that has been buried in soil due to weed harrowing, is crucial to further progress in post-emergence weed harrowing research. Up to now, crop soil cover has been assessed by visual scores, which are biased and context dependent. The aim of this study was to investigate whether digital image analysis is a feasible method to estimate crop soil cover in the early growth stages of cereals. Two main questions were examined: (1) how to capture suitable digital images under field conditions with a standard high-resolution digital camera and (2) how to analyse the images with an automated digital image analysis procedure. The importance of light conditions, camera angle, size of recorded area, growth stage and direction of harrowing were investigated in order to establish a standard for image capture and an automated image analysis procedure based on the excess green colour index was developed. The study shows that the automated digital image analysis procedure provided reliable estimations of leaf cover, defined as the as the proportion of pixels in digital images determined to be green, which were used to estimate crop soil cover. A standard for image capture is suggested and it is recommended to use digital image analysis to estimated crop soil cover in future research. The prospects of using digital image analysis in future weed harrowing research are discussed

An overlooked family-group name among bees: Availability of Coelioxoidini (Hymenoptera: Apidae)

Recent phylogenetic analysis of the family Apidae has applied the tribal name Coelioxoidini to the distinctive genus Coelioxoides Cresson, which has been thought to be related to Tetrapedia Klug.  However, the nomenclatural status of such a family-group name has not yet been assessed.  Herein, we determine that this family-group name is available and discuss its authorship and proposal date

Evasive Maneuvers

Evasive Maneuvers surveys the issue of tax havens by examining evasion terminology, evasion law, and selected relevant stories. The author uses articles and reports from the Organization for Economic Co-Operation and Development, the United States Senate, and the Internal Revenue Service, as well as from several law review articles. This paper seeks to illuminate some of the major players in the tax evasion battle and identify some of the significant types of tax evasion and avoidance techniques being used. Furthermore, the paper develops and presents the defenses and arguments of tax haven nations. Lastly, the author delves into the global impact of tax havens and discusses the future methods being implemented to combat their deleterious effects on tax revenue

Using Computational Fluid Dynamics to Predict Flow Through the West Crack Breach of the Great Salt Lake Railroad Causeway

The Great Salt Lake in Utah, USA, is a terminal, saline lake and is divided into two primary sections (northern and southern) by an east-to-west railroad causeway. Shortly after completion of the earth-fill causeway in the late 1950s, the two sections became dramatically different with differences in water surface elevation and water density. These differences cause the formation of a unique flow behavior commonly referred to as a density-driven exchange flow or bi-directional flow; a behavior observed in other lake and ocean settings where two fluids of differing densities interact. Measuring these exchange flows is a priority for lake managers who face the challenge of preserving the numerous societal and environmental benefits the lake provides. Due to rising environmental and economic concerns associated with varied lake salinity and water surface elevation, a new 50 m-wide breach was added to the railroad causeway to enhance salt and water exchange between the northern and southern sections. To support management efforts, exchange flows through the new breach were investigated using a computer modeling technique called computational fluid dynamics (CFD) supplemented by a field campaign. The results of this investigation indicate exchange flows through the breach are sensitive to fluctuations in density and water surface elevation differences in addition to the breach geometry and bathymetry. The model accurately predicted flow velocities and volumes and was used to forecast discharge through the breach as a function of the water surface elevation and density gradients under future lake conditions

Real sequence effects on the search dynamics of transcription factors on DNA

Recent experiments show that transcription factors (TFs) indeed use the facilitated diffusion mechanism to locate their target sequences on DNA in living bacteria cells: TFs alternate between sliding motion along DNA and relocation events through the cytoplasm. From simulations and theoretical analysis we study the TF-sliding motion for a large section of the DNA-sequence of a common E. coli strain, based on the two-state TF-model with a fast-sliding search state and a recognition state enabling target detection. For the probability to detect the target before dissociating from DNA the TF-search times self-consistently depend heavily on whether or not an auxiliary operator (an accessible sequence similar to the main operator) is present in the genome section. Importantly, within our model the extent to which the interconversion rates between search and recognition states depend on the underlying nucleotide sequence is varied. A moderate dependence maximises the capability to distinguish between the main operator and similar sequences. Moreover, these auxiliary operators serve as starting points for DNA looping with the main operator, yielding a spectrum of target detection times spanning several orders of magnitude. Auxiliary operators are shown to act as funnels facilitating target detection by TFs.Comment: 26 pages, 7 figure