A number of crop simulation models use as model inputs certain coefficients that account for differences among cultivars. These coefficients, often referred to as genotype coefficients, allow the models to simulate performance of diverse genotypes under different soil, weather, and management conditions. The models therefore can potentially be used to resolve the genotype × environment interaction into underlying coefficients. GENCALC (Genotype Coefficient Calculator) is a software package that facilitates the calculation of these coefficients for use in existing crop models. In GENCALC, the coefficients for a genotype are estimated iteratively by running the appropriate crop model with model input data and approximate coefficients, comparing the model output with actual data, and then altering the coefficients until the simulated and measured values match. The coefficients are determined in a specified sequence, starting with those that relate to developmental aspects. GENCALC also allows for calculation of averages (±SD) for the coefficients determined from specific experiments. This facilitates the selection of coefficients with the lowest variability, which can then be stored in crop‐specific database files. GENCALC comprises several programs and requires additional models and model input files, so a hard disk with =2 Mb free space is required. GENCALC will run on any IBM or IBM‐compatible computer with DOS version 3.0 or later.

Hunt, L. A., van

weather scenarios]roiw-heat, a number of simulation models are already available, but most of these do not appear to be set-up to facilitate easy comparison of model outputs with experimental data, to allow easy modification for new cultivars' and to facilitate the addition of disease routines, an aspect necessary for models to be useful in the general field situation. Cropsimwheat was developed to help overcome some of these deficiencies.The model assumes ttrat a crop consists of a collection of uniform plants, and performs calculations on a daily basis. It is driven by daily weather data dealing with solar radiation receipt, maxinum and minimum temperatures, and precipitation' W-ater and nitrogen u"t"o"" subroutines arl included, and the rate ofvarious crop processes is modularcd through the use of multipliers that reflect the water and nitrogen states of the crop. Developmenal processes are simulated using the concept of "biological days", a time measure that eqirates to chronological days under optimum conditions. The phases into which the life-cycle is broken relate closely to those in the widely usea "ZaAorc'; scale. Drymatter accumulation is calculated from intercepted radiatiol' and distributed largely on the basis of dtmand. A minimum fraction of daily assimilate, however, is reserved for root growth, paf area is compited on the basis of potential leaf size and available dry matter, whereas stem and spike areas are calculated from the stem a11d spike weights. Bothleaf and stem area arc used in calculating radiation inlelcenrion, Critical stresses' water saturation during *ly r""dfig growth and low temperature during the winter perid, can result in plant death. Low temperatures' when they occur around heading, can also result in sterility and reduced grain number.

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durant le remplissage du grain debl6 (Triticum aestivum L.) diffbre lorsqu'on l'6value )r I'ext6rieur ou d I'int6rieur. La pr6sente 6tude devait pr6ciser si l'6cart provient d'une variation entre la temperature de l'6pi et Ia tempdrature ambiante. On a ddtermin6 la tempdrature de l'6pi et (ou) des 9n{t9tq du bl6 cultiv6 )r I'ext6rieur et d I'int6rieur avec un thermombtre infrarouge. La temp6rature de l'6pi du bl6 cultiv6 d I'ext6rieur en pr6sence d'une quantit6 suffisante d'eau d6passait la temp6rature ambiante de 1,5'C, tandis que la temp6rature des 6pillets, telle qu'6tablie par un thermocouple, s'en rapprochait 6troitement. Lorsque le bl6 est cultiv6 ir I'intdrieur cependant, peu importe la tempdrature ambiinte, la temp6rature des 6pillets d6passe celle de 1'air de 2 d 4"C avec l'6clairage. Aprds avoir estim6 la temp6rat;re basale pour le remplissage du grain ir panir des donn6es d'une 6tude ant6rieure (bl6 cultiv6 ir l'int6rieur), .n co.p.nrunt la hausse de 3-4"C observ6e au niveau des 6pillets, on a obtenu une temp6rature basale de 8;8"C, comparable )r celle observ6e dans les essais men6es ir I'ext6rieur. L'6cart ielev6 dans les 6tudes d l'ext6rieur et )r I'int6rieur pourrait donc refl6ter la diff6rence entre la temp6rature des 6pis et la temp6rature ambiante. Estimer la temp6rature basale pour le remplissage du grain d'aprbs la temp6rature ambiante semble donc convenir pour les 6tudes poursuivies d I'ext6rieur.Mots cl6s: Triticum aestivum (L.), temp6rature basale, dur6e du remplissage du grain Can.