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Measham P.F.,University of Tasmania | Wilson S.J.,University of Tasmania | Gracie A.J.,University of Tasmania | Bound S.A.,Tasmanian Institute of Agriculture
Agricultural Water Management | Year: 2014

This study explores vascular influx of water in sweet cherry (Prunus avium L.) fruit because water is a key component of fruit quality and has been implicated in cherry fruit cracking. Flow to fruit is influenced by changing water potential of the fruit, and of potential gradients between the fruit and the spur. Water potential was influenced by vapour pressure deficit. In all seasons of this study, the most negative fruit water potential occurred in mid-afternoon when the magnitude of fruit water potential (ΨF) was greater than leaf water potential (ΨL) and analysis showed that there was a significant difference in this potential gradient between days with and without rainfall. Frequency analysis of days monitored over seasons further showed a significant association between the incidence of natural or simulated rainfall and the direction of sap flow to the fruit. This implies that manipulation of the driving forces within sweet cherry trees could be a viable management strategy for the prevention of cracking in cherry fruit. Furthermore, it suggests a role for orchard irrigation, in avoiding development of water potential gradients of fruit that favour rapid vascular influx of water following rainfall. © 2014.


Adediran S.A.,University of Tasmania | Adediran S.A.,University of Toronto | Ratkowsky D.A.,University of Tasmania | Donaghy D.J.,Tasmanian Institute of Agriculture | And 2 more authors.
Journal of Dairy Science | Year: 2012

Fourteen lactation models were fitted to average and individual cow lactation data from pasture-based dairy systems in the Australian states of Victoria and Tasmania. The models included a new "log-quadratic" model, and a major objective was to evaluate and compare the performance of this model with the other models. Nine empirical and 5 mechanistic models were first fitted to average test-day milk yield of Holstein-Friesian dairy cows using the nonlinear procedure in SAS. Two additional semiparametric models were fitted using a linear model in ASReml. To investigate the influence of days to first test-day and the number of test-days, 5 of the best-fitting models were then fitted to individual cow lactation data. Model goodness of fit was evaluated using criteria such as the residual mean square, the distribution of residuals, the correlation between actual and predicted values, and the Wald-Wolfowitz runs test. Goodness of fit was similar in all but one of the models in terms of fitting average lactation but they differed in their ability to predict individual lactations. In particular, the widely used incomplete gamma model most displayed this failing. The new log-quadratic model was robust in fitting average and individual lactations, and was less affected by sampled data and more parsimonious in having only 3 parameters, each of which lends itself to biological interpretation. © 2012 American Dairy Science Association.


McPhee J.E.,Tasmanian Institute of Agriculture | Neale T.,CTF Solutions | Aird P.L.,Serve Ag Pty Ltd
Biosystems Engineering | Year: 2013

Controlled traffic farming (CTF) maintains the same machinery wheel tracks in cropping fields year after year, thereby isolating the impacts of traffic compaction from the soil used for crop growth. The benefits of CTF include reduced energy use, improved soil health and crop yield, better timeliness of field operations and improved economics.The simplest adoption of CTF occurs in flat landscapes, and mildly sloping landscapes are an advantage in relation to surface drainage. The adoption of CTF in the Australian grain and cane industries has, to a large extent, been in flat to mildly sloping topographies. The Tasmanian vegetable industry faces a very different scenario, with topographies ranging from very flat, which present potential drainage issues, to steeply undulating, which present machine tracking and erosion challenges.Two significant challenges to the adoption of CTF in a vegetable and mixed cropping based industry were investigated - (1) working and track width compatibility of current equipment, and (2) farm layouts suited to steeply undulating topography.Farm layout can dictate success or failure in the adoption of CTF, with the risk of concentrated runoff and consequent erosion in wheel tracks. Mapping of representative farms in north-west Tasmania showed effective CTF layouts are possible, despite undulating topography and infrastructure challenges. The direction of run for many fields is already close to that required for CTF.Issues related to machinery aspects of this topic are covered in a companion paper (McPhee & Aird, 2013). © 2013 .


McPhee J.E.,Tasmanian Institute of Agriculture | Aird P.L.,Serve Ag Pty Ltd
Biosystems Engineering | Year: 2013

Controlled traffic farming (CTF) maintains the same machinery wheel tracks in cropping fields year after year, thereby isolating the impacts of traffic compaction from the soil used for crop growth. Benefits of CTF include improved energy efficiency, soil health, crop yield, timeliness and economics.The successful adoption of CTF in the Australian grain and cane industries has been largely based on a limited equipment suite and flat to mildly sloping topography. The Tasmanian vegetable industry faces a very different scenario, with a wide diversity of machinery, and topography ranging from gently to steeply undulating.Two key technical challenges to the adoption of CTF in vegetable and mixed cropping were investigated - 1) working and track width compatibility of current equipment, and 2) farm layouts suited to steeply undulating topography.Almost no machines are currently compatible with a common track or working width, although some are suitable for modification to enable CTF operation. Some harvest machinery (e.g. single row potato harvesters) provides few options for change. Seasonal CTF represents a possible starting place for adoption until more compatible machinery is available.Findings in relation to farm layouts are reported in a companion paper (McPhee, Neale, & Aird, 2013). © 2013 .


McRae J.M.,Australian Wine Research Institute | Dambergs R.G.,Australian Wine Research Institute | Dambergs R.G.,Tasmanian Institute of Agriculture | Kassara S.,Australian Wine Research Institute | And 4 more authors.
Journal of Agricultural and Food Chemistry | Year: 2012

The phenolic composition of red wine impacts upon the color and mouthfeel and thus quality of the wine. Both of these characteristics differ depending on the age of a wine, with the purple of young wines changing to brick red and the puckering or aggressive astringency softening in older wines. This study investigated the color parameters, tannin concentrations and tannin composition of a 50 year series of Cabernet Sauvignon wines from a commercial label as well as 30 year series of Cabernet Sauvignon and Shiraz wines from a separate commercial label to assess the impact of wine age on phenolic composition and concentration. The wine color density in wines of 40 to 50 years old was around 5 AU compared with 16 AU of wine less than 12 months old, which correlated well with the concentration of non-bleachable pigments and pigmented polymers. Conversely, the anthocyanin concentrations in 10 year old wines were substantially lower than that of recently bottled wines (around 100 mg/L compared with 627 mg/L, respectively), adding further evidence that non-bleachable pigments including pigmented polymers play a much larger role in long-term wine color than anthocyanins. No age-related trend was observed for tannin concentration, indicating that the widely noted softer astringency of older red wines cannot necessarily be directly related to lower concentrations of soluble wine tannin and is potentially a consequence of changes in tannin structure. Wine tannins from older wines were generally larger than tannins from younger wines and showed structural changes consistent with oxidation. © 2012 American Chemical Society.

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