Experiments conducted from 1977 to 1979, at Rutherglen, north-eastern Victoria, investigated seed production, seed longevity, seasonal emergence and phenological development in wild radish (Raphanus raphanistrum L.), a weed of field crops. Seed production of wild radish reached 17 275 seeds/m2; seeds retained viability and germinated over a period of three years. The loss of viability was faster at the soil surface or at 1 cm depth than at 5 or 10 cm. Of 1000 wild radish seeds buried at 1 cm depth, 737 emerged after three years, compared with 367, 167 and 5 at 0.5 and 10 cm, respectively. Phenological development of wild radish was affected by time of planting, and the duration of the period from plant emergence to plant senescence ranged from 5 to 10 months. Temperature appeared to influence development up to flowering, but photoperiod affected the length of flowering. Plants emerging at any time during the year were able to flower and seed successfully. The implications of these findings for control programs are discussed.

A 3-year study was conducted to measure the effect of sowing time and seeding rate on the development and yield of wheat (Triticum aestivum L.) grown under high-yielding conditions in north-eastern Victoria. A range of wheat cultivars with different development responses, including 'winter' types, was used in 2 experiments in each season. High grain yields for dryland wheat were measured in the first 2 seasons (1985-86), and in 1985, near-optimal water use efficiencies (>18 kg/ha. mm effective rainfall) were obtained. In the third season (1987) grain yield was limited by adverse climatic conditions-in the me- and post-anthesis period. In each season, grain yield declined with delay in sowing time. In 1985 there was a loss of 200-250 kg grain/ha for each week's delay in sowing time. In 1987, yield loss with delayed sowing was 50-110 kg grain/ha. In each season, cultivars with late or midseason maturity development gave the highest mean yields, and the use of these maturity types allowed earlier sowing, in mid April. However, with late sowing of wheat there was a trend for early maturity types to give higher yields, and so the use of 2 wheat cultivars with distinct maturity development responses to climate is recommended. If only 1 wheat cultivar is to be used, then a late maturity type is recommended. Higher wheat yields were also obtained as spike density increased, as a result of higher seeding rates. Our data suggest that in the higher rainfall region of north-eastern Victoria, a spike density of about 500 spikes/m2 is required to optimise wheat yields.

The effect of five densities of annual ryegrass {Lolium rigidum Gaud.) on the growth, moisture usage and grain yield of wheat at three sowing times was determined in the fieid. The presence of ryegrass reduced wheat dry matter production and grain yields by decreasing fertile tiller and fertile spikelet production. Ryegrass was more competitive in the later sown crops and its etfect on wheat grain yield was directly proportional to the square root of its density. The relationship between ryegrass density and wheat yield reduction is quantitatively described.Effet du ray-grass annuel (Lolium rigidum Gaud.) sur le rendement du bU. L'effet de cinq densit^s dc ray-grass annuel {Lolium rigidum Gaud.) sur la croissance, le taux d'humidit^ et le rendement en grain du bl^, a 6t6 d6termin6 au champ, par trois ^poques de semis. La presence du ray-grass a reduit la production dc matiere seche du b16 et le rendement en grain par diminution du nombre de talles fertiles et d'^pillets fertiles. Le ray-grass s'est montr6 plus competitif dans Ics bles sem6s tardivcment ct son effet sur Ie rendement en grain a h\t directement proportionncl k la racine carrte de sa density. La relation entre la density du ray-grass et la reduction de rendement du ble est repr^sent^e quantitativement. Die Wirkung vonLolium rigidum Gaud, auf den Weizenertrag. Es wurde die Wirkung von ftinf Dichtcn von Lolium rigidum Gaud. auT das Wachstum, den Wasscrverbrauch und den Kornertrag von Weizen bei drei verschiedcnen Saat-termincn in Feldversuchen fcstgestellt. Lolium rigidum erniedrigtc die Trockenmassen-und die Kornproduktion durch vcrringerte Bildung fcrtiler Bestockungstriebe und Ahrchen. Lolium rigidum war in der spSter gesSten Kultur konkurrenzkraftigcr und die Wirkung auf den Kornertrag war der Quadratwurzel der Dtchte direkt proportional. Die Beziehung zwischen Lolium rigidum-l>\c)\Xe und der Reduktion des Weizencrtrags ist quantitativ beschrieben.

In 1989, funding was provided to establish a large-scale (16-ha), long-term trial at Roseworthy campus. The trial aims to compare organic, biodynamic, integrated, and conventional broadacre farming systems for attributes of sustainability. It is overseen by a 13-member management committee comprising farmers with experience in each practice, agronomists, and soil scientists. Through the monitoring of indicators such as soil physical, chemical, and biological changes, product quality, economics, crop water usage, and energy requirements, the comparative advantages or disadvantages of each system are being evaluated in terms of productivity, profitability, and environmental sustainability. After 6 years, significant differences between systems are apparent in economic returns and soil available phosphorus (P) levels. The biodynamic treatment has the highest gross margins, followed by conventional, organic, and integrated. Conversely, available P levels on the biodynamic and organic treatments have declined 12 and 9%, respectively, since the start of the trial, while both the integrated and conventional treatments have increased soil P levels. In summary, it is too early in the trial to state categorically that any one system is more sustainable than another, although trends are now emerging. Weed management remains the main impediment to high production levels on the organic and biodynamic treatments, while input costs, variable yields, and low returns for grazed pastures are major constraints to high economic returns on the integrated and conventional systems.

Three experiments, begun in successive years, were conducted between 1974 and 1979 in north-eastern Victoria to investigate the effects of rotating wheat (cv. Olympic) and 'sweet' lupins (Lupinus angustifolius cv. Uniharvest) on crop yields, soil fertility and crop diseases. The grain yield of continuous wheat was 2.58 t/ha and of continuous lupins 0.66 t/ha (P<0.05). Wheat, grown after a lupin crop, yielded 750 kg/ha more than wheat after wheat, and a second wheat crop, after lupins, yielded 420 kg/ha more than a third successive wheat crop. Lupins, grown after wheat, yielded 50-165% more than lupins after lupins. Grain nitrogen of wheat was significantly increased after lupins (P<0.01). Differences in soil mineral nitrogen were apparent ten weeks after sowing, with mean nitrogen levels of 37 and 55 kg/ha under wheat and lupins, respectively. Soil mineral nitrogen (0-20 cm) was consistently greater after lupins than after wheat (P<0.01) when measured just before seeding the succeeding crop. Overall, mean accretion of mineral nitrogen under lupins was 4 1 kg/ha.year. Residual nitrogen from lupins, after one succeeding wheat crop had been grown, was also evident (mean 23 kg/ha). Crop rotation influenced the incidence of crop diseases in wheat and lupins. Lupins after lupins suffered severely from brown leaf spot (Pleiochaeta setosa), up to 63% of plants being infected compared with only 18% after wheat. Disease incidence (mainly Gaeumannomyces graminis) in wheat increased from less than 1% in the first year of cropping, to 36% infection in year 3. When wheat was grown after lupins, disease incidence was negligible.