No abstract

A field experiment was conducted to study the effects of irrigation and nitrogen applied at different growth stages on the oil and anethole yields of fennel (Foeniculum vulgare Mill.), and its yield components. Irrigation increased the yield of whole plant dry matter, with the stem elongation stage being the most sensitive. Full irrigation and irrigation applied during the flowering and late flowering growth stages increased umbel and oil yields. Irrigation during the late flowering stage made the greatest contribution to oil yield, accounting for >80% of the yield due to full irrigation. This was attributed to the concurrent timing of irrigation during the late flowering stage with dry conditions and the development of the main oil-bearing structures, the secondary and tertiary umbels. Irrigation had no significant effect on the anethole concentration of the oil. The best economic return was achieved by irrigating during the late flowering stage. There was no significant effect of nitrogen on any of the yield components measured in this study.

S U M M A R YGrowth, yield and incidence oflodging of poppies were studied in Tasmania at 10-200 plants/m 2 and at nominal rectangularities (within-row: between-row spacing) ranging from 1:1 to 10:1. In 1983/84 and 1988/89, there were asymptotic relationships between plant population density and both total dry-matter production and total head (capsule plus seed) yield at maturity. In 1983/84, a season with above-average wind, the incidence of lodging increased as density increased to > 50 plants/m 2 ; morphine concentration decreased as density increased to > 100 plants/m 2 . This resulted in parabolic relationships between yield of erect (machine-harvestable) heads and yield of morphine from erect heads with plant density, the maximum morphine yield from erect heads being achieved at 70 plants/m 2 . In 1988/89, a season with below-average wind, the effects oflodging were less severe at high densities and the components of 'erect' yield were adequately fitted by an asymptotic function. Rectangularity of 1:1 gave higher total dry matter production, total head yield, yield of erect heads and morphine yield from erect heads than 4:1 and 10:1. Since calm conditions similar to those of 1988/89 occur only once in every 4 years, growers should be encouraged to establish c. 70 plants/m 2 . As most commercial crops in Tasmania are drilled in 150-175 mm rows, growing at 70 plants/m 2 to maximize the effect of plant density would also approximate to the ideal rectangularity (2:1 in this case).

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The effects of four irrigation treatments on the growth and yield of poppies were studied in two 'drought' seasons in Tasmania. Irrigation increased total dry-matter production, leaf area index and delayed leaf senescence in both seasons. Irrigation, which continued until leaf senescence, increased total morphine yield by 5-20 kg/ha compared with no irrigation. This yield increase was attributed to the increase in the number and yield of lateral heads, the yield of terminal heads and capsule morphine concentration.As the effects of irrigation on head yield reflect the effects on total dry-matter production, irrigation guidelines for poppies were developed from an analysis of plant growth during the season. For maximum yield, one irrigation of 50 mm should be applied at the 50 % hook stage, at 50 % flowering, at the end of flowering and 2 weeks after the end of flowering. Growers who currently cease irrigation at 50 % flowering can expect yield increases of 4-13 kg/ha if they apply two further irrigations thereafter.