This paper describes the physiological basis and validation of a generic legume model as it applies to 4 species: chickpea (Cicer arietinum L.), mungbean (Vigna radiata (L.) Wilczek), peanut (Arachis hypogaeaL.), and lucerne (Medicago sativa L.). For each species, the key physiological parameters were derived from the literature and our own experimentation. The model was tested on an independent set of experiments, predominantly from the tropics and subtropics of Australia, varying in cultivar, sowing date, water regime (irrigated or dryland), row spacing, and plant population density. The model is an attempt to simulate crop growth and development with satisfactory comprehensiveness, without the necessity of defining a large number of parameters. A generic approach was adopted in recognition of the common underlying physiology and simulation approaches for many legume species. Simulation of grain yield explained 77, 81, and 70% of the variance (RMSD = 31, 98, and 46 g/m2) for mungbean (n = 40, observed mean = 123 g/m2), peanut (n = 30, 421 g/m2), and chickpea (n = 31, 196 g/m2), respectively. Biomass at maturity was simulated less accurately, explaining 64, 76, and 71% of the variance (RMSD = 134, 236, and 125 g/m2) for mungbean, peanut, and chickpea, respectively. RMSD for biomass in lucerne (n = 24) was 85 g/m2 with an R2 of 0.55. Simulation accuracy is similar to that achieved by single-crop models and suggests that the generic approach offers promise for simulating diverse legume species without loss of accuracy or physiological rigour.

Eleven genotypes of soyabean (Glycine max) of tropical, sub-tropical and temperate origin and one accession of G. soja were grown in six locations in Australia during 1986-88, and at one location in Australia and two in Taiwan during 1989-91. Dates of sowing were varied within and among locations so as to expose plants to as many as 32 environments of widely different diurnal temperature and daylength. Times from sowing to flowering (/) were recorded, from which rates of progress towards flowering (1//) were calculated. These derived data were then related to mean pre-flowering values of temperature (T) and photoperiod (P) using a threeplane linear model developed from controlled environment data. Among genotypes, mean values of/ varied between 24-49 d and between 134-291 d in the most-and least-inductive environments, respectively. These differences were associated with variations in P from about 11 to 16 h d~', in daily mean maximum temperatures from about 17° to 36°C, in daily mean minimum temperatures from about 5° to 25°C, and in T from about 11° to 30°C, that is, a very wide range of photothermal regimes. The relations of l / / t o T and P can be described in photoperiod-insensitive genotypes by a thermal plane defined by two constants, a and />, and additionally by a photothermal plane defined by three constants, a', V and c'', in the more numerous photoperiod-sensitive genotypes. If photoperiod-sensitive genotypes are grown in sufficiently long days then a third photoperiod and temperature-insensitive plane is exposed, defined by a constant, d'\ this plane indicates the maximum delay in flowering of which the Present addresses: §Queensland Department of Primary Industries, PO Box 591, Ayr, Queensland 4807, Australia; "11 Edward Crescent, Byford, Western Australia 6201. 254 R. J. SUMMERFIELD et al.genotype is capable. The constants a', b', c' and d' define the delay in flowering caused by photoperiod-sensitivity genes. The two intercepts between the three planes define, respectively, the critical photoperiod, P c , above which increase in daylength delays flowering, and the ceiling photoperiod, P ce , above which there is no further delay. The values of the six constants for any genotype can be estimated from observations of/in several natural environments. Comparisons between years in Australia and between Australia and Taiwan show that these genotypic constants can predict \/f, and so the time taken to flower, given data on latitude, sowing date and daily values of maximum and minimum air temperatures. This model is more accurate than an alternative logistic model; we also believe that all six constants in the three-plane rate model described here have biological meaning. They indicate separate genetic control of flowering responses to P and T and could form a rational basis for the genetic characterization and analysis of these responses in the soyabean germplasm. Pronostico del momento defloration II RESUMENSe cultivaron once genotipos de poroto de soja (Glyane max) de origen tropical, subtropical y te...

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.

Eight genotypes of cultivated mung bean, black gram and rice bean (Vigna mungo, Vigna radiata ssp. radiata and Vigna umbellata, respectively) were sown at six sites in Australia on various dates in order to provide a range of photothermal environments. In addition, four accessions of the related wild species Vigna radiata ssp. sublobata were sown on five occasions. Times from sowing to first flowering (/) varied between environments from 34 to 317 d; pre-flowering temperature and photoperiod means ranged from 12.7° to 29.1°C and from 11.8 to 15.5 h d~'. No effect of photoperiod was detected on rate of progress towards first flowering (1 If) in four genotypes, but in each case a significant positive relation was detected between l//*and mean temperature. These simple thermal time relations did not differ significantly among these four genotypes; the common base temperature was 7.9°C. In two genotypes observations were well described by a thermal response plane when the mean photoperiod was less than 13 h d" 1 (p < 0.01) but photoperiods greater than 14 h d~' delayed flowering. In each of the remaining genotypes the observations were best described by photothermal planes, that is, \lf was modulated by temperature and photoperiod. Predictions from the models based on our data were in good agreement with the times to first flowering observed in three genotypes in an earlier controlled environment study. 6201. 32 R. H. ELLIS et al. Pronostico del liempo hasta la floracion. IV RESUMENSe sembraron ocho genotipos de Vigna mungo, Vigna radiata ssp. radiata y Vigna umbellata en distinta fecha en seis emplazamientos en Australia a fin de proporcionar una variedad de ambientes fototermicos. Ademas, en cinco ocasiones se sembraron cuatro accesiones de las especie salvaje relacionada Vigna radiata ssp. sublobata. Los tiempos desde la siembra hasta la primera floracion (/) variaron con los distintos ambientes, de 34 d a 317 d, las medias de temperatura previa a la floracion y fotopen'odo fueron de entre 12,7°C a29,l°C, y de 11,8a 15,5 hd~'. En cuatro genotipos no se detecto efecto del fotopen'odo sobre el fndice de avance hacia la primera floracion (1 If), pero en cada uno de los casos se detecto una significativa posicion positiva entre \lfy la temperatura media. Estas relaciones de tiempo termico simple no presentaron diferencias significativas entre estos cuatro genotipos: la temperatura de base comun fue de 7,9°C. En dos genotipos las observaciones estuvieron bien representadas por un piano de respuesta termicas cuando la temperatura media fue inferior a 13 h d~ (p < 0,01), pero fotopen'odos superiores a 14 h d~ retrasaron la floracion. En cada uno de los genotipos restantes las observaciones estuvieron mejor representadas por pianos fototermicos, o sea que 1//Tue modulada por la temperatura y el fotopen'odo. Los pronosticos de los modelos basados en nuestros datos se correspondieron con los tiempos hasta la primera floracion observados en tres genotipos durante un estudio anterior en ambiente controlado.