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The effect of pH and incubation temperature on the nitrogen (N) drawdown index (NDI) of woodwaste potting media was investigated. A sand/pinebark/sawdust medium (1:1:8) was amended with seven rates of dolomite to give seven media with pH in the range 5.3 to 6.6. Nitrogen Drawdown Indices (NDI) for the addition of 75 mg N/L (NDI75) and 150 mg N/L (NDI 150 ) were measured for each medium after incubation at 10, 13, 20, and 30°C. NDI was unaffected by pH of the medium but was significantly influenced by incubation temperature. Nitrogen immobilisation was minimal at 10°C but increased with rising temperature such that at 30°C even the NDI 150 was zero. It is suggested that NDI tests be performed under conditions similar to those in which the potting media will be used in order to accurately assess potential N immobilisation under production conditions. A significant relationship between NDI assessed as NDI 75 and NDI 150 is reported. The relationship indicates that potting media with NDI 150 >0.42 and NDI 150 >0.81 will conform to the requirements of the Australian standard for regular and premium grade media respectively.

Cut flower production of 2 Australian native daisies, Helipterum roseum and Helichrysum bracteatum, was investigated in the glasshouse and outdoors at 4 planting times. Both species exhibited a long day response with floral initiation occurring in any photoperiod but with peak production following longer days. Peaks in bloom production occurred during the spring and summer regardless of planting time. Floral abnormalities were observed in Helipterum roseum in all environments and planting times with the exception of the outdoor winter planting. There was a tendency for inflorescence diameter of both species and stem length of Helipterum roseum to decline with time from anthesis of the apical inflorescence. Optimum production of top quality blooms of Helipterum roseum extended from October to January following planting between autumn and spring. Peak production of Helichrysum bracteatum between December and March can be expected following planting during winter and spring. It may be possible to extend these seasons by weekly planting from autumn to spring. In addition, the imposition of extended photoperiod or night break treatments following summer or autumn planting may fulfil the photoperiod requirements of the plants and stimulate increased production between March and November. It is proposed that both species be considered for the fresh cut flower market, with Helipterum roseum marketed as single stems and Helichrysum bracteatum as sprays.

Four granular formulations of preemergence herbicides-oxadiazon, oxadiazon in combination with simazine, dichlobenil, and oxyfluorfen + oryzalin-were evaluated for weed control and phytotoxic effects on 10 species of container-grown Australian rain forest plants. Herbicides were applied at half and at one and two times the manufacturer's recommended rate. Oxyfluorfen + oryzalin, oxadiazon, and oxadiazon + simazine controlled all weed species at half the recommended rates (1.0 + 0.5, 2.0, and 2.0 + 0.5 kg·ha-1, respectively) with no phytotoxic effects after 10 weeks to nine of the 10 rain forest species tested: broad-leafed lilly-pilly [Acmena hemilampra (F. Muell. ex Bailey) Merr. and Perry], red ash [Alphitonia excelsa (Cunn. ex Fenzl) Reisseck ex Benth.], rusty bean [Dysoxylum rufum (A. Rich.) Benth.], macaranga [Macaranga tanarius (L.) Muell. Arg.], fibrous satinash [Syzygium fibrosum (Bailey) T. Hartley and Perry], Queensland golden myrtle [Metrosideros queenslandica L.S. Smith], cluster fig [Ficus racemosa L.], corduroy tamarind [Arytera lautereriana (Bailey) Radlk.], and celerywood [Polyscias elegans (F. Muell and C. Moore) Harms]. Dichlobenil depressed plant growth of red ash and failed to control bittercress (Cardamine hirsuta L.) and green amaranth (Amaranthus viridus L.), even at twice the recommended rate (4.0 kg·ha-1). All herbicides applied at half the recommended rates produced minor to moderate plant injury within 5 weeks of the first application to corduroy tamarind and northern silky oak [Cardwellia sublimis F. Muell.]. A second application 10 weeks after the first caused no significant plant injury to corduroy tamarind but resulted in severe plant injury to northern silky oak. This finding validates the previously reported sensitivity of Proteaceous spp. to preemergence herbicides. Chemical names used: (2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-Δ2-1,3,4 oxadiazoline-5-one) (oxadiazon); (2-chloro-4,6-bisethylamino-1,3,5-triazine) (simazine); 2,6-dichlorobenzonitrile (dichlobenil); 2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene (oxyfluorfen); and 3,5-dinitro-N4,N4 -dipropylsulfanilamide (oryzalin).

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