Partial rootzone drying and deficit irrigation in cotton for use under large mobile irrigation machines

[Abstract]: There is currently a shortage of irrigation water available for cotton production in Australia due to recent climatic and legislative conditions. Some growers have responded to this water shortage by changing from traditional furrow irrigation to alternative irrigation systems such as centre pivots and lateral move irrigations (collectively known as large mobile irrigation machines – LMIMs). Improved efficiency of irrigation application, as well as labour savings, have been the main reasons for the increased adoption of LMIMs. The use of LMIMs also enables a higher level of control in water application in terms of irrigation volume, timing and placement. As a result, growers now have much greater control over soil moisture conditions which enables the implementation of improved irrigation management strategies that have the potential for improved crop water use productivity (yield/ML). Two irrigation strategies which have been demonstrated to achieve benefits in terms of crop water use are partial rootzone drying (PRD) and deficit irrigation (DI). PRD and DI involve manipulating the placement of irrigation water and the moisture deficit maintained in the root zone, respectively. Neither PRD nor DI is able to be applied easily under furrow irrigation. However, both PRD and DI may be able to be implemented under LMIMs within the Australian cotton industry. Deficit irrigation has been shown to be effective at improving water use productivity in cotton, although it is not widely used within the Australian cotton industry. Similarly, there has been little research conducted to identify whether cotton responds to partial rootzone drying and there is currently little understanding of the way in which DI and PRD strategies could be implemented commercially using LMIMs. This research carried out from 2002 to 2005 investigated the response of cotton to a range of PRD and deficit irrigation strategies for use under LMIMs. Assessment of the biochemical and physiological response of cotton to PRD and regulated deficit irrigation strategies was conducted under glasshouse conditions in Toowoomba, Qld. Field trials conducted under a commercial centre pivot and lateral move situated on the Darling Downs assessed the crop response, soil moisture movement, yield and gross production water use associated with the implementation of a range of PRD and deficit treatments. Modelling of rainfall probability and soil moisture movement were also undertaken to quantify constraints to the successful commercial implementation of irrigation management strategies such as PRD within the Australian cotton industry. PRD applied to cotton grown in split-pot containers under glasshouse conditions was found to produce a biochemical response in the form of a four fold increase in xylem Abscisic Acid concentration. The application of alternated PRD strategies was generally found to reduce both vegetative (i.e. height, leaf area) and reproductive (i.e. fruiting sites) plant growth compared to Control treatments irrigated on both sides of the plant. Increasing the period between PRD alternations from 5 to 15 days when the soil moisture potential in the wet root zone was maintained between 30 and 60 kPa also reduced the plant height and the number of fruiting sites. However, where the soil moisture in the wetted root zone was maintained at <3 kPa and alternation was based on the dry root zone moisture levels 16% (~350 kPa) and 10% (>1500 kPa) there was no difference in the major plant growth indicators (i.e. height, fruiting branches, fruiting sites, leaf area) between the various alternated PRD treatments. This suggests that the level of moisture availability in the wet root zone area is a key factor influencing water uptake and crop stress under alternated PRD conditions. No significant difference in crop growth or yield was found as a result of the PRD treatments implemented under commercial field conditions. However, this may have been attributed to the inability to apply and maintain a sufficient soil moisture gradient across the root zone to successfully induce biochemical signalling from PRD. Practical limitations in the successful application of PRD in cotton production are attributed to the soil hydraulic properties, current irrigation practices (i.e. volume and frequency of water applied) and the occurrence of in-season rainfall events. Rainfall probability and soil moisture modelling were used to evaluate the practical application of PRD within the Australian cotton industry. This work suggested thatthe creation of a soil moisture gradient across the plant root zone large enough to trigger a PRD response is most likely to be achieved on light textured soils located in semi-arid regions which experience minimal in-season rainfall events. However, the conditions are only met for a relatively small proportion of the current Australian cotton industry. Hence, it would seem that further research into the benefits of implementing PRD in cotton under LMIMs is not warranted. Regulated deficit irrigation applied under glasshouse conditions was found to have a controlling influence over partitioning between vegetative and reproductive growth. Improved physiological and gross production to water use benefits were measured as a result of deficit irrigation under field conditions and regulated deficit irrigation under glasshouse conditions. Deficit irrigation (79% of predicted ET) under field conditions produced a 31.5% improvement in gross production water use index (GPWUI = Yield / Total water applied (rainfall, irrigation and stored soil moisture)) over commercial practice (i.e. applying 100% of predicted ET). However, the largest benefits derived from deficit irrigation were associated with the management of crop agronomics (i.e. vegetative growth, retention rate and crop earliness) and the increased ability for capture of in-crop rainfall. Hence, deficit irrigation may provide substantial benefits for the cotton industry in terms of productivity of irrigation water applied as well as total water applied (irrigation, rainfall and soil moisture reserves). The ability to implement a suitable deficit irrigation strategy is regionally and seasonally dependent as the uncertainty over the timing of rainfall events and irrigation allocation both within and between seasons makes the optimal use of water resources difficult. Hence, future research should aim to enhance current crop production models to predict crop growth and response to a range of deficit irrigation treatments. Greater knowledge and adoption in the use of climatic predictors (such as SOI) are required to improve the volume and timing of deficit irrigations applied. An economics framework should be developed which encompasses resource costs and constraints on a farm basis to enable the identification of optimal management practices based on the risk profiles of the various deficit irrigation strategies. Irrigation scheduling under LMIMs is also currently limited by the use of point scale soil moisture measurements (especially under low energy precision applicator LEPA) socks) and this may be improved by the use of plant based sensors

What do gas-rich galaxies actually tell us about modified Newtonian dynamics?

It has recently been claimed that measurements of the baryonic Tully-Fisher relation (BTFR), a power-law relationship between the observed baryonic masses and outer rotation velocities of galaxies, support the predictions of modified Newtonian dynamics for the slope and scatter in the relation, while challenging the cold dark matter (CDM) paradigm. We investigate these claims, and find that: 1) the scatter in the data used to determine the BTFR is in conflict with observational uncertainties on the data; 2) these data do not make strong distinctions regarding the best-fit BTFR parameters; 3) the literature contains a wide variety of measurements of the BTFR, many of which are discrepant with the recent results; and 4) the claimed CDM "prediction" for the BTFR is a gross oversimplification of the complex galaxy-scale physics involved. We conclude that the BTFR is currently untrustworthy as a test of CDM.Comment: 5 pages, 2 figures; minor revisions to match published versio

The Limits of Anthropocene Narratives

The rapidly growing transdisciplinary enthusiasm about developing new kinds of Anthropocene stories is based on the shared assumption that the Anthropocene predicament is best made sense of by narrative means. Against this assumption, this article argues that the challenge we are facing today does not merely lie in telling either scientific, socio-political, or entangled Anthropocene narratives to come to terms with our current condition. Instead, the challenge lies in coming to grips with how the stories we can tell in the Anthropocene relate to the radical novelty of the Anthropocene condition about which no stories can be told. What we need to find are meaningful ways to reconcile an inherited commitment to narrativization and the collapse of storytelling as a vehicle of understanding the Anthropocene as our current predicament

SkyMapper Southern Survey: First Data Release (DR1)

We present the first data release (DR1) of the SkyMapper Southern Survey, a hemispheric survey carried out with the SkyMapper Telescope at Siding Spring Observatory in Australia. Here, we present the survey strategy, data processing, catalogue construction and database schema. The DR1 dataset includes over 66,000 images from the Shallow Survey component, covering an area of 17,200 deg$^2$ in all six SkyMapper passbands $uvgriz$, while the full area covered by any passband exceeds 20,000 deg$^2$. The catalogues contain over 285 million unique astrophysical objects, complete to roughly 18 mag in all bands. We compare our $griz$ point-source photometry with PanSTARRS1 DR1 and note an RMS scatter of 2%. The internal reproducibility of SkyMapper photometry is on the order of 1%. Astrometric precision is better than 0.2 arcsec based on comparison with Gaia DR1. We describe the end-user database, through which data are presented to the world community, and provide some illustrative science queries.Comment: 31 pages, 19 figures, 10 tables, PASA, accepte

Tidal tails in CDM cosmologies

We study the formation of tidal tails in pairs of merging disk galaxies with structural properties motivated by current theories of cold dark matter (CDM) cosmologies. In a recent study, Dubinski, Mihos & Hernquist (1996) showed that the formation of prominent tidal tails can be strongly suppressed by massive and extended dark haloes. For the large halo-to-disk mass ratio expected in CDM cosmologies their sequence of models failed to produce strong tails like those observed in many well-known pairs of interacting galaxies. In order to test whether this effect can constrain the viability of CDM cosmologies, we construct N-body models of disk galaxies with structural properties derived in analogy to the analytical work of Mo, Mao & White (1998). With a series of self-consistent collisionless simulations of galaxy-galaxy mergers we demonstrate that even the disks of very massive dark haloes have no problems developing long tidal tails, provided the halo spin parameter is large enough. We show that the halo-to-disk mass ratio is a poor indicator for the ability to produce tails. Instead, the relative size of disk and halo, or alternatively, the ratio of circular velocity to local escape speed at the half mass radius of the disk are more useful criteria. This result holds in all CDM cosmologies. The length of tidal tails is thus unlikely to provide useful constraints on such models.Comment: 17 pages, mn.sty, 13 included eps-figures, submitted to MNRA

An exploration of the multiplicative effect of "Other people" and other environmental effects on violence in the night-time environment

Background: The characteristics of night-time environments (NTEs) in which alcohol is consumed and that contribute to violence are poorly described. We explore competing explanations for violence in the NTE, with a particular focus on the number of patrons and its association with assault-related visits to a hospital emergency department. Other environmental features including the weather and notable events were also considered. The primary aim was to stimulate debate around the causal mechanisms responsible for violence. Methods: Assault-related ED visits occurring between 8 pm and 4 am were recorded at the University Hospital of Wales, the single Emergency Department (ED) serving Cardiff, Wales, United Kingdom. Footfall was derived from the total number of unique MAC addresses recorded per hour collected from ten wireless fidelity monitoring tools located in the city centre. A narrative review of the literature concerning alcohol and violence informed exploratory analyses into the association between night-time footfall, sporting events, the weather, and other potential predictors of assault-related visits to the ED. We developed analytic methods from formal accounts of queueing. Results: International rugby matches at home, the weather (temperature), national holidays, the day of the week, and number of patrons in the NTE predicted assault-related injury (R2 = 0.70), with footfall yielding a positive non-linear exponential association consistent with predictions derived from mathematical models of queueing. Discussion: Assault-related visits to the ED have a non-linear association with the number of people socialising in the night-time environment and are further influenced by the weather and notable events. Opportunities for further research that might inform policy and interventions aimed at better managing NTEs are discussed

Multiple Histogram Method for Quantum Monte Carlo

An extension to the multiple-histogram method (sometimes referred to as the Ferrenberg-Swendsen method) for use in quantum Monte Carlo simulations is presented. This method is shown to work well for the 2D repulsive Hubbard model, allowing measurements to be taken over a continuous region of parameters. The method also reduces the error bars over the range of parameter values due the overlapping of multiple histograms. A continuous sweep of parameters and reduced error bars allow one to make more difficult measurements, such as Maxwell constructions used to study phase separation. Possibilities also exist for this method to be used for other quantum systems.Comment: 4 pages, 5 figures, RevTeX, submitted to Phys. Rev. B Rapid Com

A Modular Toolkit for Distributed Interactions

We discuss the design, architecture, and implementation of a toolkit which supports some theories for distributed interactions. The main design principles of our architecture are flexibility and modularity. Our main goal is to provide an easily extensible workbench to encompass current algorithms and incorporate future developments of the theories. With the help of some examples, we illustrate the main features of our toolkit.Comment: In Proceedings PLACES 2010, arXiv:1110.385