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M. Stapper, C.J. Crispin, C. Davies and J.F. Angus

CSIRO Plant Industry, Canberra, ACT 2601


The ShowDevel software package links simulated wheat development with visual images of plant development and risks of weather extremes such as frosts. It will assist growers in the planning and management of wheat crops on their farm and will stimulate and support crop monitoring. ShowDevel 1.0 will be further developed and tested during 1998 for release in 1999.

Key words: Wheat phenology, modelling, plant images, frost.

Choosing a variety of the right maturity for sowing opportunities in paddocks across a farm is important to keep flowering spread over the optimum period to avoid frost damage. It is also important for scheduling timely harvesting operations to avoid weather damage and shattering risks. The optimum flowering period for winter cereals is a balance between frost risk during heading to flowering, and terminal drought and high temperatures towards maturity. Heat stress, believed to be caused by temperatures above 32oC during grain filling and ripening, impairs dough quality and should be avoided.

Towards higher production levels crops become more sensitive to the correct timing of management practices in relation to stage of plant development, for example, with topdressing and herbicide application. Seasonal weather and aspect of location (farm in district, paddocks on farm) affect crop development, making applicability of general recommendations difficult. Crop simulation models are increasingly being developed and used to support local decision making, for example, WHEATMAN (8), APSIM (3) and maNage rice (2).

Growers aiming for high yields need to be able to accurately identify crop growth stages and be aware of key crop characteristics or standards associated with high yields. Crop monitoring programs for farmers have been developed since the mid-80's, from SIRAGCROP, RiceCheck, CanolaCheck, MEY-Check to TopCrop, a national program funded by the GRDC (1). A video is available explaining wheat development and demonstrating plant observations between sowing and harvest using the decimal code of Zadoks et al. (7).

The ShowDevel package, which links wheat development calculated from weather data with visual images of plant development, will help growers to understand the interactions between sowing date, variety and stage of development as affected by temperature and day-length. It will assist growers in the planning and management of their wheat crops, and will stimulate and support crop monitoring.

Development of ShowDevel 1.0

ShowDevel 1.0 is being developed as a management aid to predict and visualise expected wheat development after selecting location and variety from pick-lists and sowing date on a time bar. ShowDevel is a Windows software package written in Delphi. Growth stages are being calculated with wheat model SIMTAG (6). Key factors simulated are leaf and tiller appearance, first node formation, flowering and maturity, with markers for last acceptable frost risk and harvest date. Calculations are based on photoperiod and mean daily temperatures, which are included in the package for over 400 locations in the Australian wheat growing areas. Temperature data are generated from latitude, longitude and altitude with ESOCLIM (4). ShowDevel 1.0 will be further developed. A heat stress indicator will be included. It will be tested during 1998 for release in 1999.

Plant animations

Images of plant development are displayed sequentially from sowing to provide on the screen an animated display of plant development concurrently with the printed model calculation. Buttons to play, stop, pause or step day-by-day forward or backward can be used with the animation. Images of growing wheat plants were developed in Corel Move. Animations of plants with 7 to 15 leaves on the main stem were developed using 134 to 206 animation frames, respectively. The user can set the speed of display from four to 25 frames per second. Final leaf number is determined in SIMTAG at floral initiation and the animation then continues using the virtual plant with that number of leaves.

Final number of leaves and nodes on main stems in a crop do vary and average in fractions, for example, 8.7 leaves and 3.4 nodes. It was, however, not possible to display plants with an unexpanded (ie. remaining fraction) final leaf or internode as the chosen software does not allow skipping the frames of remaining parts when the calculated stage has been reached. Only plants with whole numbers of leaves (7-15) and nodes (3-5) are therefore animated. Consequently, the time from flag leaf to spike emergence is being lengthened or shortened and the last node appears earlier or later to adjust to these differences.

Phenology simulation

The SIMTAG phenology component is being improved with recent crop development data from field and literature. The leaf appearance has been changed and vernalisation is being included to accommodate winter wheats. There is not yet a universal wheat development model as most models have been developed and tested with limited data sets. One of those limitations is the use of different varieties in regions and countries. Environmental effects (daylength-temperature interaction) are then translated as genotypic effects. The representativeness of air (screen) temperature for crop temperature is another matter that can be highly variable between crops (healthy-stressed), locations (soil type) and years (wet-dry). It is , therefore, very difficult to satisfactorily calibrate current models for one variety covering the whole Australian wheat belt.

Frost risk

A frost marker for the chosen location can be displayed on the time bar. Supported by experience at various locations, the last acceptable frost date in spring was defined as the 10% probability of having: (i) two days per week with minimum screen temperatures below 1.3oC or (ii) one day with a minimum temperature lower then -1oC, whichever is later. Locations were used with MetAccess (5) weather data that had 20 or more years of temperature records with a 5% tolerance for missing data. Differences in frost can be substantial between paddocks and nominated local weather station (+2 oC) as was demonstrated by the WHEATMAN project (8). Topography and aspect of weather stations are important. For example, a research station and nearby Post Office gave more than a month difference in last acceptable frost date. A more sensitive or less sensitive frost marker can be chosen by the operator if the frost risk is known to differ from the nominated location. ANUSPLIN (4) is being used to fit topographically dependent surfaces to the calculated last frost data. This will provide a systematic interrogation of these surfaces for each chosen location.


1. Andrews, R. and Till, S.G. 1996. Proc. 8th Aust. Agron. Conf. Toowoomba. pp. 64-67.

2. Angus, J.F., Williams, R.L. and Durkin, C.O. 1996. Proc. 8th Aust. Agron. Conf. Toowoomba. pp. 72-75.

3. Foale, M.A., Carberry, P.S., McCown, R.L., Probert, M.E. and Dimes, J.P. 1996. Proc. 8th Aust. Agron. Conf. Toowoomba. pp. 258-261.

4. Hutchinson, M.F., Nix, H.A., Houlder, D.J. and McMahon, J.P. 1997. ANUCLIM User Guide, Version 1.2. (Centre for Resource and Environmental Studies, ANU, Canberra.

5. MetAccess weather software. Horizon Agriculture Pty Ltd, Roseville, NSW.

6. Stapper, M. 1984. SIMTAG: a Simulation Model of Wheat Genotypes. Model Documentation. ICARDA, Syria and University of New England, Armidale. 108 pp.

7. Stapper, M. 1987. Identification of Development Stages in Wheat. SIRAGCROP Video. NSW Agriculture Media Unit, Orange.

8. Woodruff, D.R. 1989. Proc. 5th Aust. Agron. Conf. Perth. p. 665.

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