Commercially suitable methods for application of fluazinam were evaluated in field trials conducted in Victoria and Western Australia. Incorporation of fluazinam into the soil in bands 23 cm wide along the transplant row (to a depth of about 15–20 cm) immediately before transplanting was the most effective method of application. Plants grown in soil treated in this way developed significantly less clubroot than when fluazinam was applied using either a spot drench (100 mL/plant) or a continuous spray over the plants immediately after transplanting. The banded soil incorporation treatment consistently increased the marketable yield of broccoli and cauliflower. In one trial, banded soil incorporation increased the marketable yield of both crops by at least 80% compared with the other commercial methods of application currently in use. The banded soil incorporation treatment was more reliable and effective in a range of soil types than the high volume drenches currently used. This method of application remained effective, significantly reducing clubroot severity, when the volume of water used to apply fluazinam was reduced by 80% from 2500 to 500 L/ha.
Summary. Spraytopping, the application of a low rate of non-selective herbicide (usually glyphosate or paraquat) to annual grass seed heads in the spring or early summer for seed set control is widely practised throughout Australia. While grasses are the targets of the spray treatment, annual pasture legumes may also be damaged by spraytopping, particularly if the legumes are flowering at the time of application. The effect of applying glyphosate (90, 112 or 162 g a.i./ha), paraquat (100 g a.i./ha) and glyphosate plus MCPA (90 + 150 g a.i./ha) to subterranean clover (Trifolium subterraneum L. cv. Dalkeith) and annual medic (Medicago polymorpha L. cvv. Serena, Santiago and Circle Valley) pastures at various times during flowering was investigated during the spring of 1993 and 1994. Experiments were located at Tincurrin and Tenindewa, Western Australia. Subterranean clover seed yield was most affected by applications of glyphosate (90 and 162 g a.i./ha) and glyphosate plus MCPA (90 + 150 g a.i./ha) during early–mid flowering. Seed yield was reduced by as much as 88% following application of glyphosate plus MCPA when 20% of the subterranean clover plants were flowering. Treatment with paraquat (100 g a.i./ha) during mid–late flowering reduced seed yield of subterranean clover by 25–50% in experiment 1 only. Medic seed yield was reduced up to 90% depending on cultivar when glyphosate (112 g a.i./ha) was applied during early–mid flowering. In addition to seed yield, the level of hard seed was assessed. Treatment of subterranean clover during early–mid flowering with glyphosate (90 and 162 g a.i./ha) significantly reduced the quantity of hard seed produced. Thirty–forty percent of subterranean clover seed was germinable soon after seed set, compared with 7–17% germinable for the seed from untreated plants. Treatment with glyphosate (112 g a.i./ha) reduced the proportion of hard seed in the medics when applied during mid flowering. Treatment with paraquat had little effect on the proportion of hard seed formed. This work demonstrates that using a spraytopping technique for control of seed set in annual grasses may dramatically reduce seed yield in pasture legumes. Spraytopping can further reduce the ability of legumes to persist in cropping rotations by reducing the amount of hard seed formed. Implications for practical farming systems are outlined.
2The nitrogen (N) requirements of two Australian crisp potato (Solanum tuberosum L.) varieties, Bliss and Dawmor, were compared with Atlantic in experiments over three years on loamy sands and sands in the south west of Western Australia. There was a significant response of yield to rate of applied nitrogen (N) and variety on all sites and a significant nitrogen by varietal interaction on sands. Yield increased to a maximum with rate of applied N and then decreased above this rate on sites on loamy sands and or reached a plateau with no yield decrease (exponential response) at high rates of applied N on sands. Nitrate (NO 3 )-N concentration (mg kg −1 DW) in petioles required for maximum yield of Atlantic decreased linearly (P < 0.05) from 23,947 at the 10 mm tuber stage to 13,052 at the 60 mm tuber stage, in Dawmor from 22,429 to 14,644 and in Bliss from 20,202 to 12,597 over the same tuber stages. Bliss tubers had the highest specific gravity (SG) on both soil types and Dawmor the lowest on loamy sands. The effect of rate of applied N and variety on crisp cooking color, internal defects (hollow heart and internal brown spot) of tubers and tuber nutrient concentration is also discussed.
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