Rohan Nelson and Howard Cox

Whopper Cropper is a software tool designed to apply cropping systems modelling and seasonal climate forecasting to crop management in farmer-driven workshops. It was developed in response to a demand by extension professionals for access to the cropping systems modelling capability of APSIM and seasonal climate forecasting using the Southern Oscillation Index (SOI). It provides information on the impact of climate risk on crop yields for crop management alternatives beyond the experience of individual farmers, using historical climate records to obtain a long term perspective. Whopper Cropper's graphical user interface is designed to support workshops that enable farmers to explore management strategies at the beginning of each cropping season.

Climate and market risk threaten the efficiency and sustainability of cropping systems in the grain/cotton belt of northern New South Wales and Queensland, and one policy response has been to enhance farmers' ability to manage risk. Australia's northern grainbelt has an extremely variable climate, with highly variable rainfall rarely exceeding evaporative demand in any month (Scoccimarro et al. 1994, Hammer et al. 1996). There is evidence that climatic variability can lead to poor intuitive judgement. For example, Hayman et al (1996) reported that farmers’ estimates of the distribution of wheat and sorghum yields had a lower mean and a higher variance than those suggested by the APSIM mdoel. This bias was attributed to the influence on farmers' judgement of boom and bust seasons experienced in the previous 5 years.

Crop management decisions can be supported using decision support systems that simulate the effects of management and climate variability on crop yields. Decision support systems can organise and process large quantities of information, helping farmers to identify and concentrate on the most important information for each management decision (Kearney 1992). Feedback regarding earlier decision support systems such as FCDA and Wheatman has highlighted the need for risk management decision support systems in agriculture to focus on farming outcomes such as yields and gross margins. Providing data to managers, such as rainfall, increases the information surrounding complex management decisions, but may not help managers focus on the outcomes that are important to them. Consequently, Whopper Cropper is designed to provide distributions of crop yields that enable the likely impact of management options to be rapidly evaluated.

Whopper Cropper was developed in response to a demand by extension professionals for access to the cropping systems modelling capability of the APSIM model (McCown et al. 1996) and to seasonal climate forecasting using the SOI phase forecasting system of Stone et al. (1996). It was developed using an iterative development process that involved extension professionals, the target user group, from the first prototype. Through this feedback process, Whopper Cropper developed into a software tool that extension professionals could use interactively in discussion with farmers about management options. An evolving recognition of the effectiveness of Whopper Cropper in this role has led the development team to refer to it as a discussion support system.

Whopper Cropper (Nelson et al. 1999) is a database of pre-run APSIM simulations with an easy-to-use graphical interface facilitating time series, probability and diagnostic analyses. To create the Whopper Cropper database, a team of researchers from the Agricultural Production Systems Research Unit (APSRU) have used the APSIM model to simulate a variety of crops with different starting soil conditions and management options, for 16 regions between Gunnedah in Central New South Wales and Clermont in Central Queensland. Whopper Cropper's graphical user interface can be used to view probability distributions of crop yields by SOI phase to discuss the best management options for the coming season. Future versions of Whopper Cropper will include a facility to simulate distributions of gross margins, using Monte-carlo simulation to combine distributions of yield and price for each crop management option.

The Whopper Cropper database and graphical user interface are currently distributed to accredited operators via CD, with 2 CDs required to accommodate the current database. Extension professionals become accredited users through a one-day training course providing an overview of crop modelling, seasonal climate forecasting and decision analysis. The training module focuses on how to use the software in farmer-driven workshops to analyse cropping options prior to each summer and winter cropping season.

Whopper Cropper has been designed to support workshops in which farmers can explore crop management options for the coming season. Much of the development of these workshops has taken place in Central Queensland, and they can be readily adapted to other areas for which the APSIM model has been validated.

Yield outcomes are very variable in Central Queensland (Figure 1). The mean sorghum yield associated with a positive SOI phase for September/October is 1000 kg/ha greater than that for a negative SOI. Whopper Cropper provides insight into the management options that may be varied to improve the reliability of crop production. Growers can explore management strategies by varying area sown, forward selling, N fertiliser input, irrigation planning, plant density and other crop choices etc.

Figure 1 Comparison of grain yields of sorghum sown in November at Biloela with negative and positive SOI phases for September/October (170mm PAWC 67% full medium maturity, 7 plants/m², 50 kgN/ha)

If the SOI remains near zero (Spring 2000) through September and October there is little difference in the potential outcome from a November or a January sowing time (Figure 2). However, if the SOI became positive, November sowing opportunities offer an advantage in terms of expected yield. This last occurred in spring 1998 when several local growers took advantage of the opportunity. However, if the SOI became negative, as it was in spring 1997, the January sowing time appears slightly more favourable.

Figure 2: Modelled yield distributions of sorghum sown in November or January with three SOI phases for September and October (170mm PAWC, 67% full, medium maturity, 7 plants/m²)

Whopper Cropper was developed in response to a growing demand from extension professionals for access to cropping systems modelling and seasonal climate forecasting to enhance the management of cropping systems. The development and extension of Whopper Cropper is an incremental step in the evolution of decision/discussion support systems in Australian Agriculture, focusing on management outcomes rather than farming system inputs. Whopper Cropper enables users to easily manipulate and view a wide range of crop management options, and evaluate likely outcomes given current seasonal climate forecasting information. It has proved to be an effective discussion support system for enhancing the management of climate risk in cropping systems.