The APSIM Soybean Module -(soybean)

Introduction

The soybean module was developed Michael Robertson with contributions from Peter Carberry. APSIM-Soybean belongs to the PLANT family of crop modules in APSIM. The reader is referred to the science document for the plant module for a comprehensive description of the processes simulated by APSIM-Soybean. This document outlines some soybean-specific issues that are not covered by the legume science document.

Notable features of APSIM-SOYBEAN

• The phenology of soybean cultivars are responsive to temperature and photoperiod, but not vernalisation. There is no photoperiod effect on post-flowering duration, even though it is known that such an effect exists.

• There are a limited number of cultivars available and users should consult the module owner if they need advice specifying a new cultivar

• Account is taken of the energy costs involved in synthesising the high energy content grain in soybean.

• Oil content is not simulated dynamically in response to any cultivar or environmental effects.

• APSIM-Soybean is not phosphorus-responsive, this is currently under development.

• Crop growth is not sensitive to waterlogging.

• The module does not simulate the differences between determinant and indeterminant types in terms of canopy expansion and flowering.

Cultivars and crop classes

There are two crop classes. One is the conventional type, and the other is a promiscuous nodulator, often grown in the developing world. The promiscuous crop class has low N fixation capacity.

There are 8 cultivars able to be simulated: Davis, Buchanan, CPI26671, Durack, Valiant, Roan, Magoye and Dragon. Cultivars differ in terms of biomass partitioning to grain and phenology. Cultivar Magoye, listed below, is a promiscuous type. It has a lower harvest index.

Validation

APSIM-Soybean has received testing across northern Australia, with factors such as cultivars, sowing date, irrigation, soil type, plant population density row spacing varying. Papers describing validation of APSIM-Soybean are by Robertson and Carberry (1998) and Denner et al. (1998). The accompanying figure demonstrates the performance of the module against Australian datasets.

Figure 1: Performance of the soybean module (observed versus simulated grain yield in g/m2) against test datasets reported by Robertson and Carberry (1998).

References

Denner, M. T.; James, A. T.; Robertson, M. J., and Fukai, S. 1998. Optimum soybean cultivars for possible expansion area: a modelling approach. Proceedings 10th Australian Soybean Conference, Brisbane 15-17 September, 1998:137-141.

Robertson, M. J. and Carberry, P. S. 1998. Simulating growth and development of soybean in APSIM. Proceedings 10th Australian Soybean Conference, Brisbane 15-17 September, 1998:130-136.