Modelling Soil Organic Matter Dynamics – Global Challenges - Sustainable Management of Soil Organic Matter - page 66

P.J.Thorburnet al. ModellingDecomposition of Sugarcane Surface Residues

2.4

Modelling Decomposition of
Sugarcane Surface Residues
and the Impact on Simulated
Yields

P.J. T HORBURN 1 , F.A. R OBERTSON 2 , S.N. L ISSON 3
AND J.S. B IGGS 1

1
CSIRO Tropical Agriculture, 306CarmodyRd, St Lucia Qld 4067;
2
CRC for Sustainable Sugar Production,BSES,PMB57, Mackay
MC, Qld 4740; and 3 CRC for Sustainable Sugar Production and
CSIROTropical Agriculture,PMB, POAitkenvale, Queensland
4814, Australia

Introduction

The Agricultural Productions Systems Simulator (APSIM; McCown et al .,
1996) describes the dynamics of crop growth (for various crops), soil water,
soil nitrogen (N) and carbon (C), and plant residues as a function of cli-
mate, cropping history (e.g. crop type, sowing date) and soil management
(e.g. tillage, fertilizer application). APSIM's linking of crop growth with soil
water and N/C dynamics makes it particularly suited for extrapolating the
results of agronomic experiments to different soil, management and/or
climatic conditions (Probert et al ., 1995, 1998b; McCown et al ., 1996;
Keating et al ., 1997). Despite its wide application for this purpose, to date
some APSIM modules have been developed and tested in grain and
legumes systems in semiarid, rain-fed areas (Probert et al ., 1995, 1998a,b;
Carberry et al ., 1996) and so could benefit from wider testing. This
is particularly so of the APSIM-Residue module that describes the

decomposition of surface residues.
Recently, increasing attention has been paid to the impact of crop
residue retention on soil water and N dynamics of sugarcane systems in the
environmentally sensitive humid coastal areas of Australia. APSIM pro-
vides a means of modelling these systems (Keating et al ., 1997; Thorburn
et al ., 1999). While the overall agreement between measured and modelled
data has been good (Thorburn et al ., 1999), the climate, soils and
agronomic characteristics (e.g. residue mass, N fertilizer application rates,