Scoping RD&E priorities for waterlogging susceptible irrigated production systems in Tasmania using the APSIM farming systems model

[摘要] The recent expansion of irrigation schemes in the state of Tasmania has stimulated interest in the productive capacity of irrigated enterprises, and the optimum management strategies to maximise profitability while minimising impacts on the environment. While field experimentation can be used to investigate these questions, the modelling of agricultural production systems is also a widely accepted approach for conducting such investigations.While the APSIM model has achieved widespread use for simulating farming systems on mainland Australia, its application in farming systems research in Tasmania has been infrequent. Of particular concern among Tasmanian researchers is the ability of APSIM to simulate waterlogging, which typically occurs during the winter months when rainfall is high, evaporative demand is low, and regional groundwater tables (or perched water tables) rise into the crop root zone.In order to address these concerns, we conducted a ‘ground-truthing’ exercise with the objective of determining (1) whether APSIM could accurately simulate wheat growth and development (including water and nitrogen use) in a waterlogged field in Tasmania, and (2) what are the major model parameterisation and science limitations (if any) that complicate the application of APSIM in this system. In order to answer these questions, existing data sets were initially used to parameterise and calibrate APSIM to waterlogged production fields, after which standard APSIM parameterisations were adjusted for a number of site and region specific issues. Subsequently, simulation results were assessed to develop potential RD requirements that would inform more extensive farming systems analysis in the region.The results showed that APSIM could be used to successfully simulate the fluctuations in a water table, while accurately simulating soil nitrate across the course of the season, despite an extended period of waterlogging. The results also suggest that extended waterlogging during the vegetative growth phase did not have a direct negative impact on crop production in the 2009/2010 season, but reduced soil N and so reduced crop production-potential indirectly through restricted N supply.Results of the study also enabled (1) identification of primary RD knowledge gaps throughout the soil and plant systems i.e. those that prevent precise calibration of the model to the system in question, and (2) identification of production system constraints and potential management options (or environmental implications of these) that can be immediately scoped using the calibrated model, albeit with appropriate reference to assumptions made during the calibration process. Thus the study also illustrated the benefits of using APSIM as an analytic tool within a farming system.Further research is necessary to determine the extent of waterlogging across the range of soils in Tasmania, the frequency, duration and severity with which waterlogging occurs, and at what growth stage (if any) waterlogging begins to impact directly on crop growth. A range of other research questions were also identified, along with recommendations to improve future collection of field data to assist with model ground-truthing.

[发布机构] CSIRO

[学科分类] 地球科学(综合)