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K. Verburg1, B.A. Keating2, K.L. Bristow3, N.I. Huth2, and P.J. Ross3

1CSIRO Division of Soils, 306 Carmody Road, St Lucia, Qld 4067
CSIRO Division of Tropical Crops and Pastures, 306 Carmody Road, St Lucia, Qld 4067
CSIRO Division of Soils, PMB, PO Aitkenvale, Townsville, Qld 4814

Agricultural management decisions must increasingly consider production, profit and environmental impacts of whole systems. Some of the system components are, however, difficult or impossible to measure directly. Combining measurement with modelling is therefore becoming an increasingly used methodology. The comprehensive modelling capability that has been developed within the APSIM (3) framework is particularly suited to this approach. Recently the soil-water model SWIMv2 (5), which is based on the Richards’ and advection-dispersion equations, has been interfaced with APSIM (1). This combination allows a detailed description of the movement of water and solutes in the soil to be combined with other plant, soil and environmental modules available in APSIM. In this poster we show how APSIM-SWIM can be used to examine management strategies that might limit nitrate leaching under sugarcane crops.


The experimental data used in this evaluation come from a field study in Bundaberg, Qld (which is funded in part by SRDC and LWRRDC). The fate of a combined application of N-fertiliser and bromide tracer was monitored by regular soil sampling during the 1992/93 season. Soil hydraulic properties were obtained in the field (hydraulic conductivity near saturation) and using undisturbed soil cores in the lab (water retention curves). APSIM-SWIM was configured to run with a crop module for sugarcane (2) and a soil nitrogen module (SOILN) (4).


Based on the assumption that nitrate will move in a similar fashion to bromide, the first step was to test the solute transport model using the bromide tracer data. Satisfactory predictions were obtained throughout the growing season. Good agreement between model results and experimental data was also obtained for nitrogen movement and uptake. These results provided confidence for the next step of examining strategies for managing water and nitrogen fertiliser. An example of such a strategy is presented and evaluated in terms of its impact on crop production and nitrate leaching.


1. Huth, N.I., Keating, B.A., Bristow, K.L. and Verburg, K. 1996. Proc. 8th Aust. Agronomy Conf., Toowoomba, Qld.

2. Keating, B.A., Robertson, M.J., Muchow, R.C. and Huth, N.I. 1996. Proc. 8th Aust. Agronomy Conf., Toowoomba, Qld.

3. McCown, R.L., Hammer, G.L., Hargreaves, J.N.G., Holzworth, D.P. and Freebairn, D.M. 1995, Agric. Systems 49 (in press).

4. Probert, M.E., Dimes, J.P., Dalal, R.C. and Strong, W.M. 1996. Proc. 8th Aust. Agronomy Conf., Toowoomba, Qld.

5. Ross, P.J., Bristow,K.L., Bailey, S.W. and Smettem, K.R.J. 1992. Agronomy Abstracts. Proc. 1992 Annual Meetings of the Am. Soc. Agronomy, Minneapolis, U.S.A. p.83.

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