The Interactive Effect of Pruning Level and Irrigation Strategy on Water Use Efficiency of Vitis vinifera L. cv. Shiraz

A partial rootzone drying (PRD) irrigation technique (0.5 ML/ha) was compared with a standard irrigation treatment(1 ML/ha) at three different pruning levels of 30, 60 and 120 nodes per grapevine in Vitis vinifera L. cv Shiraz. The PRDirrigation technique was applied to a single side of the grapevine rootzone at a time, 45 cm from the trunk, and the sideswere switched in 10-day cycles. For the standard irrigation treatment, both sides of the grapevine were irrigated. At theend of an irrigation cycle, the PRD treatment resulted in reduced midday readings of stomatal conductance and stem (ψS)and leaf (ψL) water potential relative to the control treatment. During the switch between irrigation cycles, when the soilwater profile of both the ‘wet’ and ‘dry’ sides of the PRD-treated grapevines was refilled, stomatal conductance, ψS andψL were restored to the same levels as for the control experiment. As node number per grapevine increased, berry size andwinter pruning weight were reduced and yield increased. In the first season of the experiment, the PRD treatment did nothave a significant effect on berry size, yield and pruning weight, although shoot length was reduced in response to PRD forall the pruning treatments. In a subsequent season, PRD was found to reduce yield, primarily through a reduction in berryset. Water use efficiency measured as t/ML irrigation water applied was increased significantly as crop load increased, andwas enhanced in response to the PRD irrigation technique

The Interactive Effect of Pruning Level and Irrigation Strategy on Grape Berry Ripening and Composition in Vitis vinifera L. cv. Shiraz

A partial rootzone drying (PRD) irrigation technique (0.5 ML/ha) was compared with a standard irrigation treatment(1 ML/ha) at three different pruning levels of 30, 60 and 120 nodes per grapevine in Vitis vinifera L. cv Shiraz. Berrysize was found to decrease as node number per grapevine increased, but was not significantly altered by the PRDtreatment. The influence of these treatments on the accumulation of total soluble solids per berry was investigatedduring berry ripening and was shown to be reduced at higher node number (120 nodes). There was no effect ofPRD on the accumulation of total soluble solids. Juice titratable acidity and the concentration (per g) and content(per berry) of grape anthocyanins and phenolics were compared between treatments at harvest. In one season ofthe study, juice titratable acidity, anthocyanin and phenolic concentration was unaltered by the PRD treatment. Ina further season, juice titratable acidity was decreased in response to the PRD treatment and was associated withincreases in grape anthocyanin and phenolic concentration in response to PRD. Where there was a small increasein anthocyanin concentration in response to PRD, this was found to be independent of berry size. In addition, linearregression analysis showed a poor relationship between berry size and anthocyanin concentration, but a significantrelationship was found between berry size and anthocyanins per berry

A Preliminary Investigation on Partial Rootzone Drying (PRD) Effects on Grapevine Performance, Nitrogen Assimilation and Berry Composition

Partial rootzone drying (PRD) is an irrigation management technique designed to reduce water use in grapevines without a decline in yield, thereby increasing water use efficiency (WUE). Experiments consisted of field-grown Cabernet Sauvignon, where the PRD grapevines were irrigated with half the amount of water as control grapevines, and Shiraz, where the PRD grapevines received the same amount of water as control grapevines.  PRD treatments showed no significant differences in yield or berry composition at harvest, except that PRD grapevines that received half the amount of water had significantly smaller berries than control grapevines. Cabernet Sauvignon PRD grapevines receiving half the amount of water as control grapevines showed a 34 % reduction in main shoot growth and up to a 74% reduction in lateral shoot growth. Shoot growth was inhibited to a lesser extent in Shiraz PRD grapevines receiving the same amount of water, with a 20% reduction in main shoot.growth and a 33% reduction in lateral shoot growth. PRD also significantly reduced stomatal conductance in Cabernet Sauvignon on average by 31 % and 16% in Shiraz. Nitrate reductase (NR) activity in grapevine leaves was significantly lowered in response to PRD, irrespective of the amount of water applied. The reduction in NR activity was closely correlated with the development of the PRD cycle and the associated reduction in stomatal conductance

1H and 13C solution- and solid-state NMR investigation into wax products from the Fischer-Tropsch process

(1)H and (13)C solid- and solution-state NMR have been used to characterise waxes produced in the Fischer-Tropsch reaction, using Co-based catalysts either unpromoted or promoted with approximately 1 wt% of either cerium or rhenium. The aim was to measure average structural information at the submolecular level of the hydrocarbon waxes produced, along with identification of the minor products, such as oxygenates and olefins, which are typically observed in these waxes. A parameter of key interest is the average number of carbon atoms within the hydrocarbon chain (N(C)). A wax prepared using an unpromoted Co/Al(2)O(3) catalyst had N(C)similar to 20, whilst waxes made using rhenium- or cerium-promoted Co/Al(2)O(3) catalysts were found to have N(C)similar to 21. All three samples contained small amounts of oxygenates and alkenes. The subtle differences found in the waxes, in particular the minor species produced, demonstrate that the different promoters have different effects during the reaction, with the Re-promoted catalyst producing the fewest by-products. It is shown in (13)C solid-state NMR spectra that for that for longer chain (compared to the lengths of chain in previous studies) waxes that the lack of resolution and the complexities added by the differential cross-polarisation (CP) dynamics mean that it is difficult to accurately determine N(C) from this approach. However the N(C) determined by (13)C CP magic angle spinning NMR is broadly consistent with the more accurate solution approaches used and suggest that the wax characteristics do not change in solution. On this basis an alternative approach for determining N(C) is suggested based on (1)H solution state NMR that provides a higher degree of accuracy of the chain length as well as information on the minor constituents

Potential of partial rootzone drying as an alternative irrigation technique for potatoes (Solanum tuberosum)

The increasing demands on limited water supplies worldwide require the adoption of more efficient irrigation techniques for sustainable production in agriculture. Partial rootzone drying (PRD) is one of the techniques that offer potential saving of irrigation water. This technique involves alternate irrigation to two sides of a plant root system. The studies reported here investigated PRD irrigation regimes and the optimum time of starting PRD in potatoes grown in a protected environment. In the first experiment, plants of the potato cv. Estima were exposed to five different irrigation treatments and a fully watered control at tuber initiation. The treatment that performed most similar to the control was alternate PRD to field capacity (APRD100). This treatment produced similar total leaf area, haulm fresh and dry weights, plant water status and no significant yield reduction compared with the control plants. The APRD100 treatment utilised 29% less water and increased water use efficiency (WUE) by 19%. In the second experiment, the APRD100 irrigation was started at 2, 4, 6, 8 and 10 weeks after plant emergence. Vegetative growth and yield increased with the delay of the APRD100. APRD100 started at 6 weeks after emergence did not significantly reduce fresh tuber yield but received 21% less total water with a 19% increase in WUE. The results indicate that PRD may have potential use in the potato crop for conserving irrigation water with minimal loss of yield. <br