The influence of nutrient solution adjustment and replacement (management), its electrical conductivity (EC) and plant spacing on yield and quality of strawbeny fruit (var. Torrey) produced in a recirculating hydroponic system was studied at Gosford, New South Wales. Four ways of managing the nutrient solution were examined: (i) pH and EC adjusted daily and the solution replaced every 8 weeks (current grower practice); (ii) as above except that a topping up solution with lower potassium to nitrogen (K: N) ratio was used for EC adjustment; (iii) no daily adjustment of EC or pH and one-third of solution replaced every 2 weeks; and (iv) no daily adjustment of solution volume, EC or pH and full replacement after 8 weeks. Compared with grower practice, these alternative solution management strategies provided no advantage in yield, fruit number, or in the �Brix, citric acid, sweetness or flavour of fruit. Use of a topping up solution supplemented with ammonium nitrate (NH4NO3) and calcium nitrate [Ca(NO3)2] to reduce the K : N ratio from 1.7:1.0 to 1.4:1.0 had no effect (P>0.05) on yield but significantly increased (P<0.05) berry weight and improved fruit aroma. Regardless of which method of nutrient solution adjustment and replacement was used, the chemical composition of the recirculating solution changed markedly over 53 days. The method of nutrient solution management significantly (P<0.05) affected leaf phosphorus (P), calcium (Ca), magnesium (Mg), manganese (Mn), and zinc (Zn) but only Mg fell to a suboptimal level for growth of strawberries. Reducing the EC of the nutrient solution from 3 to 2 dS/m at early fruit set gave heavier (P<0.05) berries compared with constant EC of 2 dS/m. Increasing the EC from 2 to 3 or reducing it from 3 to 2 at early fruit set resulted in sweeter (P<0.05) berries and reducing the EC from 4 to 2 improved fruit aroma. Yield declined (P<0.05) when EC was increased from 2 to 4 dS/m. Solution EC bad significant effects (P<0.05) on leaf P, Mg, Mn and Zn. An increase in planting density from 5.35 to 9.35 plants/m2 lowered (P<0.05) marketable yield per plant and fruit acidity but gave 41% higher (P<0.05) yield on an area basis.

Girdling, thinning and trimming bunches and gibberellic acid (GA) treatments were imposed on sultana vines over three years to study their effects on berry size, yield, skin strength, pedicel features and bunch characteristics. A double cut stem girdle (4.8 mm) combined with three GA sprays of 60 p.p.m. (applied at bloom, shatter and two weeks after shatter) and bunch thinning and trimming produced large berries weighing up to 5 g each. However this treatmen1 delayed fruit maturity and produced more compact bunches. Similar sized berries with no delay in maturity and looser bunches were obtained by using the same combination of treatments but reducing the GA sprays to two, one at 10 p.p.m. applied at 50 per cent bloom and the second at 60 p.p.m, at 3-4 mm berry diameter, which was two weeks after shatter. A double cut was more effective than a single cut girdle. Bunch thinning and trimming were necessary for best results but there were no differences in results between trimming to four or six laterals per bunch. Thinning to 15 bunches per vine produced more compact bunches and lower yield than 20 bunches per vine. Berry skin resistance to puncture was increased more effectively by bunch trimming and thinning than by girdling or applying GA. Pedicel length and thickness were increased substantially by applying GA.

Effects of trellising together with the use of various foliage wire arrangements on the production and quality of harvest-pruned sultanas were studied over 4 years. In one experiment a single wire and four narrow 0.4 m 'T' trellis systems, and in a second experiment four 0.9 m wide 'T' trellis and one 0.4 m narrow 'T' trellis system, were tested. Other treatments superimposed on all trellises included crown bunch removal in early spring or at harvest pruning, one and two alkaline oil-in-water sprays (oil sprays) and gibberellic acid (GA) or no GA spray. There were no differences between the four narrow trellises. Dried fruit yield of these four trellises was greater than that of the single wire by an average of 27%, because of higher bunch and cane numbers. There were also no differences between the four wide trellises except that two of the complex ones had more canes. The narrow trellis NTI (used in both experiments) yielded 27% less than the wide trellises because of fewer bunches per vine, caused by lower cane numbers and fruitfulness. Trellising had no effect on fruit quality and only marginal effects on rate of fruit drying, most probably due to low vigour of the experimental vines. As the complex trellis systems had no advantage over the simpler two wire 'T' trellises, their use in harvest pruning is not advocated. In both experiments two oil sprays produced slightly better fruit quality with faster drying of fruit. Use of two oil sprays is warranted where fruit has to be dried rapidly to minimise risk due to rain damage. Early crown bunch removal did not reduce yield and the best time for bunch removal was 6 weeks after bud burst. Use of GA in harvest pruning is not recommended as it does not improve fruit quality and in some years leads to slower fruit drying.

No abstract

The long-term, annual application of nitrogen (N), phosphorus (P), and potassium (K) to the drip area of Valencia orange trees growing in a Tiltao sandy loam soil in the Sunraysia district of the lower Murray was investigated for its effect on soil pH, Bray 1 extractable soil P, and exchangeable cations calcium (Ca), magnesium (Mg), K, sodium (Na), and aluminium (Al) at 5 soil depths.Nitrogen (applied as ammonium nitrate) generally lowered soil pH to a depth of 30 cm, the effect increasing with rate of applied N. At 20 cm depth, the highest rate of applied N (450 kg/ha) reduced soil pH from 7.6 to 3.9, while 150 kg N/ha resulted in a soil pH of 5.0. Consequently, levels of exchangeable Ca, Mg, K, and Na in the soil were lower. There was a strong negative correlation between soil A1 and soil pH. At soil depths of 10-30 cm, the highest rate of applied N resulted in high levels (>20%) of exchangeable A1 as a proportion of the effective cation exchange capacity (CEC). Available soil P increased with rate of applied P, but the effect decreased with depth. Significantly (P<0.05) increased levels of available P were found to 30 cm depth when P was applied at 30 and 90 kg/ha, and to 60 cm depth at 180 kg P/ha. At 180 kg P/ha, Ca from superphosphate decreased Mg to 60 cm depth. Soil K levels were higher with increased rate of applied K and increased soil depth. The highest rate of applied K (360 kg/ha) depressed available P to 90 cm depth. Exchangeable Mg, K and Na percentages of the CEC in most treatments and at most soil depths were above the desirable range. Soil Na levels for some treatments and depths approached the level for sodic soils.