In recent years, many sorghum producers in the more marginal (<600 mm annual rainfall) cropping areas of Queensland and northern New South Wales have used skip row configurations in an attempt to improve yield reliability and reduce sorghum production risk. This paper describes modifications made to the APSIM sorghum module to account for the difference in water usage and light interception between alternative crop planting configurations, and then demonstrates how this new model can be used to quantify the long-term benefits of skip sorghum production. Detailed measurements of light interception and water extraction from sorghum crops grown in solid, single and double skip row configurations were collected from on-farm experiments in southern Qld and northern NSW. These measurements underpinned changes to the APSIM-Sorghum model so that it accounted for the elliptical water uptake pattern below the crop row and the reduced total light interception associated with skip row configurations. Long-term simulation runs using long-term weather files for locations near the experimental sites were used to determine the value of skip row sorghum production as a means of maintaining yield reliability. These simulations showed a trade-off between long-term average production (profitability) and annual yield reliability (risk of failure this year). Over the long term, the production of sorghum in a solid configuration produced a higher average yield compared with sorghum produced in a skip configuration. This difference in average yield is a result of the solid configuration having a higher yield potential compared with the skip configurations. Skip configurations limit the yield potential as a safeguard against crop failure. To achieve the higher average yield in the solid configuration the producer suffers some total failures. Skip configurations reduce the chance of total failure by capping the yield potential, which in turn reduces the long-term average yield. The decision on what row configuration to use should be made tactically and requires consideration of the starting soil water, the soil’s plant-available water capacity (PAWC), and the farm family’s current attitude to risk.

. Relationships between planting date, winter survival and stress tolerances of soft white winter wheat in eastern Ontario. Can. J. Plant Sci. 77: 507-513. Reduction of populations of fall planted crops in the course of winter can result in substantial losses in economic yield. Variations in planting date of soft white winter wheat (Triticum aestivum L.) in eastern Ontario are known to influence both survival and grain yield. This study was conducted to determine relationships between fall-accumulated growing degree days (GDD), cold hardiness, ice tolerance and a number of plant characteristics with survival recorded the next spring. Locations were at Ottawa (45°23′N) and Douglas (45°33′N) with four planting dates, 27 August, 10 September, 24 September and 8 October in 4 yr, 1983-1986. Delayed planting was associated with reduced survival at Ottawa in 1987 and in all years at Douglas. Consequently, survival at Ottawa showed little association with cold hardiness and ice tolerance, but there were significant correlations at Douglas. Measurements in 3 yr showed that late planted wheats were single tillered, up to 10 times lower fresh weight than the 3-5 tillered August-planted wheat, and their cold hardiness and ice tolerance were decreased. Moisture content of the crown tissue (CrW) increased with delayed planting despite the growth of the plants in acclimating conditions. Highest CrW developed in late-planted wheat at Douglas and showed a high negative correlation with survival. Cold hardiness and ice tolerance correlated with survival at Douglas and there were significant relationships between the stress tolerances. However, no consistent associations across location-years could be defined to explain winter survival in terms of fall-measured stress tolerances and plant parameters. Key words:Cold acclimation, cold hardiness, crown moisture, winter injury, ice encasement, delayed planting Andrews, C. J., Pomeroy, M. K., Seaman, W. L., Butler, G., Bonn, P. C. et Hoekstra, G. 1997. Liens existants entre la date de semis, le taux de survie à l'hiver et la tolérance aux stress chez le blé d'automne blanc tendre dans l'est de l'Ontario. Can. J. Plant Sci. 77: 507-513. La baisse de densité de peuplement qu'on observe en hiver dans les cultures semées en automne peut se solder par des pertes importantes de rendement économique. Il est connu que les variations de la date de semis du blé d'automne blanc tendre (Triticum aestivum L.) dans l'est de l'Ontario peuvent influer à la fois sur le degré de survie à l'hiver et sur le rendement grainier. Nous avons voulu élucider les rapports existants entre les sommes de température en automne (degrés-jours de croissance), la rusticité hivernale, la tolérance à l'englacement et quelques autres caractères de la culture avec le degré de survie mesuré le printemps suivant. Les essais se déroulaient quatre années de suite (1983 à 1986) à Ottawa, 45°33′N et à Douglas (45°23′N) à 4 dates de semis soit le 27 août, le 10 et le 24 septembre et le 8 octobre. Les semis tardifs donnaient génér...