Regulated deficit irrigation - a means to control growth in woody ornamentals

Improving plant quality and the uniformity of a crop are major objectives for growers of ornamental nursery stock. The potential to control excess vigour and to improve quality through regulated deficit irrigation (RDI) was investigated using a range of woody ornamental species. RDI regimes reduced vegetative growth consistently across different species and growing seasons. Plants adapted to reduced water supplies primarily via stomatal control, but also by osmotic adjustment when grown under the most severe RDI regimes. Only plants exposed to <= 25% of potential evapo-transpiration demonstrated any evidence of leaf injury, and the extent was slight. Growth inhibition increased as the severity of RDI increased. Improvements in quality were attained through a combination of shorter internodes and final shoot lengths, yet the number of 'formative' primary shoots remained unaffected. Compact, well-branched plants could be formed without a requirement for mid-season pruning. In addition to severity, the timing of RDI also influenced growth responses. Applying 50% ETp for 8 weeks during July-August resulted in the formation of good quality plants, which retained their shape until the following Spring. Re-positioning irrigation drippers within the pots of well-watered plants, in an attempt to induce a partial root drying (PRD) treatment, reduced growth, but not significantly. The adoption of irrigation scheduling, based on 50-100% ETp, has the potential to improve commercial crop quality across a range of ornamental species.

Regulation of plant growth in container-grown ornamentals through the use of controlled irrigation

The aim of this research was to determine whether shoot growth could be regulated and plant quality improved through two controlled irrigation techniques: Regulated Deficit Irrigation (RDI) or Partial Root Drying (PRD). An additional benefit of such techniques is that they would also improve the efficiency of irrigation application and reduce the volume of water used on commercial nurseries. Results from two ornamental woody plant species (Cotinus and Forsythia) demonstrated that plant quality could be significantly improved when RDI was applied at ≤ 60% of potential evapo-transpiration (ETp). Stomatal closure and reduced leaf and internode growth rates were associated with both the RDI and PRD techniques, but reduced leaf water potential was only recorded in the RDI system. Changes in xylem sap pH and ABA concentrations were correlated with changes in shoot physiology, and thought to be generated by those roots exposed to drying soil. By adopting such controlled irrigation systems on commercial holdings it is estimated that water consumption could be reduced by 50 to 90%.

Use of HNO3 as the source of NO to prepare a nitric oxide complex of ruthenium

Reaction of cis-Ru(bisox)(2)Cl-2, where bisox is 4,4,4',4'-tetramethyl-2,2'-bisoxazoline, with HNO3 in 1 : 4 molar proportion in boiling water under N-2 atmosphere and subsequent addition of an excess of NaClO4 center dot H2O yields [Ru(bisox)(HL)(NO)](ClO4)(NO3) (1). HL is a hydrolysed form of bisox where one of the oxazoline rings opens up. X-Ray crystallography shows that 1 contains an octahedral RuN5O core. HL binds the metal through an imino N, an amide N and an alcoholic O atom. Reaction of cis-Ru(bisox)(2)Cl-2 with an excess of NaNO2 in water gives cis-Ru(bisox)(2)(NO2)(2) (2). On acidification by HClO4 in methanol, 2 is smoothly converted to cis-[Ru(bisox)(2)(NO2)(NO)](ClO4)(2) (3) due to equilibrium (1).

Diet, fecal water, and colon cancer - development of a biomarker

Colorectal cancer (CRC) is a leading cause of cancer incidence worldwide. Lifestyle factors, especially dietary intake, affect the risk of CRC development. Suitable risk biomarkers are required in order to assess the effect that specific dietary components have on CRC risk. The relationship between dietary intake and indicators of fecal water activity has been assessed using cell and animal models as well as human studies. This review summarizes the literature on fecal water and dietary components with a view to establishing further the potential role of fecal water as a source of CRC risk biomarkers. The literature indicates that fecal water activity markers are affected by specific dietary components linked with CRC risk: red meat, saturated fats, bile acids, and fatty acids are associated with an increase in fecal water toxicity, while the converse appears to be true for calcium, probiotics, and prebiotics. However, it must be acknowledged that the study of fecal water is still in its infancy and a number of issues need to be addressed before its usefulness can be truly gauged.

Link between DOC in near surface peat and stream water in an upland catchment

Hydrologic transport of dissolved organic carbon (DOC) from peat soils may differ to organo-mineral soils in how they responded to changes in flow, because of differences in soil profile and hydrology. In well-drained organo-mineral soils, low flow is through the lower mineral layer where DOC is absorbed and high flow is through the upper organic layer where DOC is produced. DOC concentrations in streams draining organo-mineral soils typically increase with flow. In saturated peat soils, both high and low flows are through an organic layer where DOC is produced. Therefore, DOC in stream water draining peat may not increase in response to changes in flow as there is no switch in flow path between a mineral and organic layer. To verify this, we conducted a high-resolution monitoring study of soil and stream water at an upland peat catchment in northern England. Our data showed a strong positive correlation between DOC concentrations at − 1 and − 5 cm depth and stream water, and weaker correlations between concentrations at − 20 to − 50 cm depth and stream water. Although near surface organic material appears to be the key source of stream water DOC in both peat and organo-mineral soils, we observed a negative correlation between stream flow and DOC concentrations instead of a positive correlation as DOC released from organic layers during low and high flow was diluted by rainfall. The differences in DOC transport processes between peat and organo-mineral soils have different implications for our understanding of long-term changes in DOC exports. While increased rainfall may cause an increase in DOC flux from peat due to an increase in water volume, it may cause a decrease in concentrations. This response is contrary to expected changes in DOC exports from organo-mineral soils, where increase rainfall is likely to result in an increase in flux and concentration.

Approximate Riemann solutions of the two-dimensional shallow-water equations

A finite-difference scheme based on flux difference splitting is presented for the solution of the two-dimensional shallow-water equations of ideal fluid flow. A linearised problem, analogous to that of Riemann for gasdynamics, is defined and a scheme, based on numerical characteristic decomposition, is presented for obtaining approximate solutions to the linearised problem. The method of upwind differencing is used for the resulting scalar problems, together with a flux limiter for obtaining a second-order scheme which avoids non-physical, spurious oscillations. An extension to the two-dimensional equations with source terms, is included. The scheme is applied to a dam-break problem with cylindrical symmetry.

An efficient numerical scheme for the two-dimensional shallow water equations using arithmetic averaging

A finite difference scheme based on flux difference splitting is presented for the solution of the two-dimensional shallow water equations of ideal fluid flow. A linearised problem, analogous to that of Riemann for gas dynamics is defined, and a scheme, based on numerical characteristic decomposition is presented for obtaining approximate solutions to the linearised problem, and incorporates the technique of operator splitting. An average of the flow variables across the interface between cells is required, and this average is chosen to be the arithmetic mean for computational efficiency leading to arithmetic averaging. This is in contrast to usual ‘square root’ averages found in this type of Riemann solver, where the computational expense can be prohibitive. The method of upwind differencing is used for the resulting scalar problems, together with a flux limiter for obtaining a second order scheme which avoids nonphysical, spurious oscillations. An extension to the two-dimensional equations with source terms is included. The scheme is applied to the one-dimensional problems of a breaking dam and reflection of a bore, and in each case the approximate solution is compared to the exact solution of ideal fluid flow. The scheme is also applied to a problem of stationary bore generation in a channel of variable cross-section. Finally, the scheme is applied to two other dam-break problems, this time in two dimensions with one having cylindrical symmetry. Each approximate solution compares well with those given by other authors.

Speciation and variation in the occurrence of haloacetic acids in three water supply systems in England

An investigation into the speciation and occurrence of nine haloacetic acids (HAAs) was conducted during the period of April 2007 to March 2008 and involved three drinking water supply systems in England, which were chosen to represent a range of source water conditions; these were an upland surface water, a lowland surface water and a groundwater. Samples were collected seasonally from the water treatment plants and at different locations in the distribution systems. The highest HAA concentrations occurred in the upland surface water system, with an average total HAA concentration of 21.3 μg/L. The lowest HAA levels were observed in the groundwater source, with a mean concentration of 0.6 μg/L. Seasonal variations were significant in the HAA concentrations; the highest total HAA concentrations were found during the autumn, when the concentrations were approximately two times higher than in winter and spring. HAA speciation varied among the water sources, with dichloroacetic acid and trichloroacetic acid dominant in the lowland surface water system and brominated species dominant in the upland surface water system. There was a strong correlation between trihalomethanes and HAAs when considering all samples from the three systems in the same data set (r2=0.88); however, the correlation was poor/moderate when considering each system independently.

Oxygen isotope composition of bivalve seasonal growth increments and ambient water in the rivers Rhine and Meuse

The application of oxygen isotope ratios ({delta}18O) from freshwater bivalves as a proxy for river discharge conditions in the Rhine and Meuse rivers is investigated. We compared a dataset of water temperature and water {delta}18O values with a selection of recent shell {delta}18O records for two species of the genus Unio in order to establish: (1) whether differences between the rivers in water {delta}18O values, reflecting river discharge conditions, are recorded in unionid shells; and (2) to what extent ecological parameters influence the accuracy of bivalve shell {delta}18O values as proxies of seasonal, water oxygen isotope conditions in these rivers. The results show that shells from the two rivers differ significantly in {delta}18O values, reflecting different source waters for these two rivers. The seasonal shell {delta}18O records show truncated sinusoidal patterns with narrow peaks and wide troughs, caused by temperature fractionation and winter growth cessation. Interannual growth rate reconstructions show an ontogenetic growth rate decrease. Growth lines in the shell often, but not always, coincide with winter growth cessations in the {delta}18O record, suggesting that growth cessations in the shell {delta}18O records are a better age estimator than counting internal growth lines. Seasonal predicted and measured {delta}18O values correspond well, supporting the hypothesis that these unionids precipitate their shells in oxygen isotopic equilibrium. This means that (sub-) fossil unionids can be used to reconstruct spring-summer river discharge conditions, such as Meuse low-discharge events caused by droughts and Rhine meltwater-influx events caused by melting of snow in the Alps.

In vitro bioaccessibility and gut biotransformation of polyphenols present in the water-insoluble cocoa fraction

Scope: Cocoa, especially the water-insoluble cocoa fraction (WICF), is a rich source of polyphenols. In this study, sequential in vitro digestion of the WICF with gastrointestinal enzymes as well as its bacterial fermentation in a human colonic model system were carried out to investigate bioaccessibility and biotransformation of WICF polyphenols, respectively. Methods and results: The yield of each enzymatic digestion step and the total antioxidant capacity (TAC) were measured and solubilized phenols were characterized by MS/MS. Fermentation of WICF and the effect on the gut microbiota, SCFA production and metabolism of polyphenols was analyzed. In vitro digestion solubilized 38.6% of WICF with pronase and Viscozyme L treatments releasing 51% of the total phenols from the insoluble material. This release of phenols does not determine a reduction in the total antioxidant capacity of the digestion-resistant material. In the colonic model WICF significantly increased of bifidobacteria and lactobacilli as well as butyrate production. Flavanols were converted into phenolic acids by the microbiota following a concentration gradient resulting in high concentrations of 3-hydroxyphenylpropionic acid (3-HPP) in the last gut compartment. Conclusion: Data showed that WICF may exert antioxidant action through the gastrointestinal tract despite its polyphenols being still bound to macromolecules and having prebiotic activity.

Sub-irrigation of Petunia: benefits in dry summers

With the increasing frequency and magnitude of warmer days during the summer in the UK, bedding plants which were a traditional part of the urban green landscape are perceived as unsustainable and water-demanding. During recent summers when bans on irrigation have been imposed, use and sales of bedding plants have dropped dramatically having a negative financial impact on the nursery industry. Retaining bedding species as a feature in public and even private spaces in future may be conditional on them being managed in a manner that minimises their water use. Using Petunia x hybrida ‘Hurrah White’ we aimed to discover which irrigation approach was the most efficient for maintaining plants’ ornamental quality (flower numbers, size and longevity), shoot and root growth under water deficit and periods of complete water withdrawal. Plants were grown from plugs for 51 days in wooden rhizotrons (0.35 m (h) x 0.1 m (w) x 0.065 m (d)); the rhizotrons’ front comprised clear Perspex which enabled us to monitor root growth closely. Irrigation treatments were: 1. watering with the amount which constitutes 50% of container capacity by conventional surface drip-irrigation (‘50% TOP’); 2. 50% as sub-irrigation at 10 cm depth (‘50% SUB’); 3. ‘split’ irrigation: 25% as surface drip- and 25% as sub-irrigation at 15 cm depth (‘25/25 SPLIT’); 4. 25% as conventional surface drip-irrigation (‘25% TOP’). Plants were irrigated daily at 18:00 apart from days 34-36 (inclusive) when water was withdrawn for all the treatments. Plants in ‘50% SUB’ had the most flowers and their size was comparable to that of ‘50% TOP’. Differences between treatments in other ‘quality’ parameters (height, shoot number) were biologically small. There was less root growth at deeper soil surface levels for ‘50% TOP’ which indicated that irrigation methods like ‘50% SUB’ and ‘25/25 SPLIT’ and stronger water deficits encouraged deeper root growth. It is suggested that sub-irrigation at 10 cm depth with water amounts of 50% container capacity would result in the most root growth with the maximum flowering for Petunia. Leaf stomatal conductance appeared to be most sensitive to the changes in substrate moisture content in the deepest part of the soil profile, where most roots were situated.

Dispersion of a point-source release of a passive scalar through an urban-like array for different wind directions

The dispersion of a point-source release of a passive scalar in a regular array of cubical, urban-like, obstacles is investigated by means of direct numerical simulations. The simulations are conducted under conditions of neutral stability and fully rough turbulent flow, at a roughness Reynolds number of Reτ = 500. The Navier–Stokes and scalar equations are integrated assuming a constant rate release from a point source close to the ground within the array. We focus on short-range dispersion, when most of the material is still within the building canopy. Mean and fluctuating concentrations are computed for three different pressure gradient directions (0◦ , 30◦ , 45◦). The results agree well with available experimental data measured in a water channel for a flow angle of 0◦ . Profiles of mean concentration and the three-dimensional structure of the dispersion pattern are compared for the different forcing angles. A number of processes affecting the plume structure are identified and discussed, including: (i) advection or channelling of scalar down ‘streets’, (ii) lateral dispersion by turbulent fluctuations and topological dispersion induced by dividing streamlines around buildings, (iii) skewing of the plume due to flow turning with height, (iv) detrainment by turbulent dispersion or mean recirculation, (v) entrainment and release of scalar in building wakes, giving rise to ‘secondary sources’, (vi) plume meandering due to unsteady turbulent fluctuations. Finally, results on relative concentration fluctuations are presented and compared with the literature for point source dispersion over flat terrain and urban arrays. Keywords Direct numerical simulation · Dispersion modelling · Urban array

Catchment phosphorous losses: an export coefficient modelling approach with scenario analysis for water management

This paper presents the development of an export coefficient model to characterise the rates and sources of P export from land to water in four reservoir systems located in a semi-arid rural region in southern of Portugal. The model was developed to enable effective management of these important water resource systems under the EU Water Framework Directive. This is the first time such an approach has been fully adapted for the semi-arid systems typical of Mediterranean Europe. The sources of P loading delivered to each reservoir from its catchment were determined and scenario analysis was undertaken to predict the likely impact of catchment management strategies on the scale of rate of P loading delivered to each water body from its catchment. The results indicate the importance of farming and sewage treatment works/collective septic tanks discharges as the main contributors to the total diffuse and point source P loading delivered to the reservoirs, respectively. A reduction in the total P loading for all study areas would require control of farming practices and more efficient removal of P from human wastes prior to discharge to surface waters. The scenario analysis indicates a strategy based solely on reducing the agricultural P surplus may result in only a slow improvement in water quality, which would be unlikely to support the generation of good ecological status in reservoirs. The model application indicates that a reduction of P-inputs to the reservoirs should first focus on reducing P loading from sewage effluent discharges through the introduction of tertiary treatment (P-stripping) in all major residential areas. The fully calibrated export coefficient modelling approach transferred well to semi-arid regions, with the only significant limitation being the availability of suitable input data to drive the model. Further studies using this approach in semi-arid catchments are now needed to increase the knowledge of nutrient export behaviours in semi-arid regions.

Natal nest locations of the Asian house rat (Rattus tanezumi) in lowland rice–coconut cropping systems: a coconut penthouse or rice bunds with water frontage?

CONTEXT. Rattus tanezumi is a serious crop pest within the island of Luzon, Philippines. In intensive flood-irrigated rice field ecosystems of Luzon, female R. tanezumi are known to primarily nest within the tillers of ripening rice fields and along the banks of irrigation canals. The nesting habits of R. tanezumi in complex rice–coconut cropping systems are unknown. AIMS. To identify the natal nest locations of R. tanezumi females in rice–coconut systems of the Sierra Madre Biodiversity Corridor (SMBC), Luzon, during the main breeding season to develop a management strategy that specifically targets their nesting habitat. METHODS. When rice was at the booting to ripening stage, cage-traps were placed in rice fields adjacent to coconut habitat. Thirty breeding adult R. tanezumi females were fitted with radio-collars and successfully tracked to their nest sites. KEY RESULTS. Most R. tanezumi nests (66.7%) were located in coconut groves, five nests (16.7%) were located in rice fields and five nests (16.7%) were located on the rice field edge. All nests were located above ground level and seven nests were located in coconut tree crowns. The median distance of nest sites to the nearest rice field was 22.5m. Most nest site locations had good cover of ground vegetation and understorey vegetation, but low canopy cover. Only one nest location had an understorey vegetation height of less than 20 cm. CONCLUSIONS. In the coastal lowland rice–coconut cropping systems of the SMBC, female R. tanezumi showed a preference for nesting in adjacent coconut groves. This is contrary to previous studies in intensive flood-irrigated rice ecosystems of Luzon, where the species nests mainly in the banks of irrigation canals. It is important to understand rodent breeding ecology in a specific ecosystem before implementing appropriate management strategies. IMPLICATIONS. In lowland rice–coconut cropping systems, coconut groves adjacent to rice fields should be targeted for the 20 management of R. tanezumi nest sites during the main breeding season as part of an integrated ecologically based approach to rodent pest management.

Poisoning the mind: Arsenic contamination of drinking water wells and children's educational achievement in rural Bangladesh

Bangladesh has experienced the largest mass poisoning of a population in history owing to contamination of groundwater with naturally occurring inorganic arsenic. Prolonged drinking of such water risks development of diseases and therefore has implications for children's cognitive and psychological development. This study examines the effect of arsenic contamination of tubewells, the primary source of drinking water at home, on the learning outcome of school-going children in rural Bangladesh using recent nationally representative data on secondary school children. We unambiguously find a negative and statistically significant correlation between mathematics scores and arsenic-contaminated drinking tubewells at home, net of the child's socio-economic status, parental background and school specific unobserved correlates of learning. Similar correlations are found for an alternative measure of student achievement and subjective well-being (i.e. self-reported measure of life satisfaction), of the student. We conclude by discussing the policy implication of our findings in the context of the current debate over the adverse effect of arsenic poisoning on children.