Simulation models for strategic and tactical management of crops and pastures

Abstract

Australian crops and pastures are grown in climates which are relatively variable at present and may become more variable if the global climate changes. Optimal management in relation to this variability has two strands. The best-bet management strategy must be identified for the long-term climate and modified with any climate change. Variation in weather between years, however, is already greater than changes in the mean expected from climate change, so improved management tactics to cope with current variabilitywill lead to systems with longterm resilience. Examples using the SIMTAG and maNage models are described for improved strategic and tactical management of rainfed wheat. SIMTAG is used to clarify the extent to which regional yields are currently limited by weather and to make a strategic assessment of optimal sowing date. The maNage model is used for tactical management of supplementary N fertiliser for dryland wheat. maNage shows that the reliability of yield response is increased if the N is applied at the terminal spikelet stage but only ifthe amount of stored soil water is above a defined threshold. Future integration of crop models with pasture models is discussed. Pastures make up the largest landuse on farms in the region. They have special importance because they influence the growth of crops grown in sequence. Modelling the interaction of pastures-crop sequences and crop-crop sequences in relation to weather is important for increasing yields ofboth crops and pastures. © 1993, The Society of Agricultural Meteorology of Japan. All rights reserved.